Spatial distribution and seasonal variation in Undaria pinnatifida ...
Spatial distribution and seasonal variation in Undaria pinnatifida ...
Spatial distribution and seasonal variation in Undaria pinnatifida ...
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Waikato Regional Council Technical Report 2013/15<strong>Spatial</strong> <strong>distribution</strong> <strong>and</strong><strong>seasonal</strong> <strong>variation</strong> <strong>in</strong> <strong>Undaria</strong>p<strong>in</strong>natifida populations aroundthe Corom<strong>and</strong>el Pen<strong>in</strong>sulawww.waikatoregion.govt.nzISSN 2230-4355 (Pr<strong>in</strong>t)ISSN 2230-4363 (Onl<strong>in</strong>e)
Prepared by:Kate James <strong>and</strong> Nick Shears,Leigh Mar<strong>in</strong>e LaboratoryUniversity of Auckl<strong>and</strong>For:Waikato Regional CouncilPrivate Bag 3038Waikato Mail CentreHAMILTON 3240July 2012Document #: 2340351
Approved for release by:Peter S<strong>in</strong>gletonDate April 2013DisclaimerThis technical report has been prepared for the use of Waikato Regional Council as a referencedocument <strong>and</strong> as such does not constitute Council’s policy.Council requests that if excerpts or <strong>in</strong>ferences are drawn from this document for further use by<strong>in</strong>dividuals or organisations, due care should be taken to ensure that the appropriate contexthas been preserved, <strong>and</strong> is accurately reflected <strong>and</strong> referenced <strong>in</strong> any subsequent spoken orwritten communication.While Waikato Regional Council has exercised all reasonable skill <strong>and</strong> care <strong>in</strong> controll<strong>in</strong>g thecontents of this report, Council accepts no liability <strong>in</strong> contract, tort or otherwise, for any loss,damage, <strong>in</strong>jury or expense (whether direct, <strong>in</strong>direct or consequential) aris<strong>in</strong>g out of the provisionof this <strong>in</strong>formation or its use by you or any other party.Doc # 2340351
<strong>Spatial</strong> <strong>distribution</strong> <strong>and</strong> <strong>seasonal</strong> <strong>variation</strong> <strong>in</strong> <strong>Undaria</strong> p<strong>in</strong>natifida populationsaround the Corom<strong>and</strong>el Pen<strong>in</strong>sulaJuly 2012Kate James <strong>and</strong> Nick ShearsLeigh Mar<strong>in</strong>e LaboratoryUniversity of Auckl<strong>and</strong>kjam015@auckl<strong>and</strong>uni.ac.nz,A report prepared for the Waikato Regional Council
11. Executive Summary<strong>Undaria</strong> p<strong>in</strong>natifida (hereafter called <strong>Undaria</strong>) was first officially recorded <strong>in</strong> the Hauraki Gulf, on mussel farm <strong>in</strong>frastructure<strong>in</strong> the Firth of Thames, <strong>in</strong> 2002, <strong>and</strong> subsequently at Hobson West Mar<strong>in</strong>a <strong>in</strong> the Waitemata Harbour <strong>in</strong> 2004. The warmerwaters of the Hauraki Gulf had been considered to be outside the optimal range for <strong>Undaria</strong> growth. However, this hasproven to be <strong>in</strong>accurate. Prior to this report no quantitative <strong>in</strong>formation was available on the <strong>distribution</strong> or ecology of<strong>Undaria</strong> populations <strong>in</strong> the Corom<strong>and</strong>el region.Between November 2011 <strong>and</strong> February 2012 spatial surveys were carried out to <strong>in</strong>vestigate the <strong>distribution</strong> of <strong>Undaria</strong>populations <strong>and</strong> the level of <strong>in</strong>festation present on mussel farms <strong>and</strong> adjacent coastal sites around the Corom<strong>and</strong>elPen<strong>in</strong>sula. In addition, beg<strong>in</strong>n<strong>in</strong>g <strong>in</strong> June 2011 <strong>Undaria</strong> populations were monitored monthly at two sites with<strong>in</strong>Corom<strong>and</strong>el Harbour <strong>and</strong> fortnightly at two sites at Westhaven Mar<strong>in</strong>a <strong>in</strong> the Waitemata Harbour.Sites where mussel farms are established provide suitable habitat for <strong>Undaria</strong> growth. The water quality, flow <strong>and</strong> nutrientlevels required for mussel farm<strong>in</strong>g are <strong>in</strong> l<strong>in</strong>e with ideal <strong>Undaria</strong> grow<strong>in</strong>g conditions <strong>and</strong> the well-illum<strong>in</strong>ated, artificialstructures promote <strong>Undaria</strong> establishment without competition from other macroalga. A survey of <strong>Undaria</strong> was conductedacross all mussel farm sites <strong>and</strong> large areas of adjacent coastl<strong>in</strong>e around the Corom<strong>and</strong>el Pen<strong>in</strong>sula. Further areas of<strong>in</strong>terest surveyed were high use public boat ramps, sw<strong>in</strong>g moor<strong>in</strong>gs, Hannaford’s Jetty <strong>and</strong> the mussel load<strong>in</strong>g facility atTe Kouma. At each site environmental data was collected <strong>and</strong> <strong>in</strong>formation on <strong>Undaria</strong> population structure <strong>and</strong> densitywere recorded. Other <strong>in</strong>vasive species present were also recorded.<strong>Undaria</strong> was found to be widespread on mussel farms around the Corom<strong>and</strong>el Pen<strong>in</strong>sula. It is well established on musselfarm structures from Moturua Isl<strong>and</strong> to Wilson Bay on the west coast of the Corom<strong>and</strong>el Pen<strong>in</strong>sula. Although notprevalent, dur<strong>in</strong>g this survey, on mussel farms at Kennedy Bay or Port Charles, <strong>Undaria</strong> was found on artificial substrateat these sites. Thirty one mussel farms were surveyed, levels of <strong>Undaria</strong> <strong>in</strong>festation were def<strong>in</strong>ed as low to medium (1-100plants per 50 m length of mussel l<strong>in</strong>e) on seventeen, high (>100 plants per 50 m of mussel l<strong>in</strong>e) on eleven <strong>and</strong> <strong>Undaria</strong>was not seen on three farms. Higher density populations were found at poorly ma<strong>in</strong>ta<strong>in</strong>ed mussel farms <strong>and</strong> on mussell<strong>in</strong>es with large mussels, 80-120mm. The exception to this was the high densities of <strong>Undaria</strong> at all mussel farms surveyedat the Wilson Bay Mar<strong>in</strong>e Farm<strong>in</strong>g Zone (WBMFZ) <strong>in</strong> the Firth of Thames, a well ma<strong>in</strong>ta<strong>in</strong>ed site. The vigour <strong>and</strong> density ofthe population seen with<strong>in</strong> the WBMFZ, by far the largest aquaculture site surveyed, may be due to the fact that this is themost long-established population. The size <strong>and</strong> nature of the WBMFZ ensures a constant <strong>and</strong> immense supply of sporesat this site. This high propagule pressure is likely to perpetuate the dense population at this site despite differ<strong>in</strong>g stages ofmussel growth <strong>and</strong> l<strong>in</strong>e/float rotation at <strong>in</strong>dividual farms with<strong>in</strong> the site. Further <strong>in</strong>vestigation <strong>in</strong>to environmental <strong>in</strong>fluencescould reveal other factors promot<strong>in</strong>g the growth <strong>and</strong> proliferation of <strong>Undaria</strong> at this site. <strong>Undaria</strong> is likely spread betweenmussel farms, <strong>in</strong> its sporophyte or microscopic gametophyte phase, via fouled mussel barge hulls, mussel farm<strong>in</strong>gequipment (such as ropes <strong>and</strong> floats) <strong>and</strong> with mussel spat.<strong>Undaria</strong> has not extensively <strong>in</strong>vaded coastal reef areas adjacent to mussel farms. Approximately 12km of coastl<strong>in</strong>eadjacent to mussel farms was surveyed around the Corom<strong>and</strong>el Pen<strong>in</strong>sula. <strong>Undaria</strong> was found at six out of the twenty sixcoastal sites surveyed. This is the first time <strong>Undaria</strong> has been recorded on the Corom<strong>and</strong>el Coast. Total numbersrecorded at any coastal site were between two <strong>and</strong> fifty plants, <strong>in</strong>clud<strong>in</strong>g reproductively mature plants. Relatively lowdensities at coastal sites could reflect poor dispersal to coastal sites, high levels of predation <strong>and</strong> competition <strong>in</strong> theseareas, <strong>in</strong>sufficient time to allow extensive populations to establish <strong>in</strong> these coastal reef communities, or <strong>seasonal</strong> lows dueto the tim<strong>in</strong>g of some of the surveys.No <strong>Undaria</strong> was found at the mussel load<strong>in</strong>g facility/boat ramp at Te Kouma, the sw<strong>in</strong>g moor<strong>in</strong>g sites at W<strong>in</strong>dy po<strong>in</strong>t/PuheRare <strong>and</strong> Takawhare Bay, Hannaford’s Jetty or the two other boat ramp sites surveyed at Colville <strong>and</strong> Waikawau.Monitor<strong>in</strong>g studies found <strong>Undaria</strong> plants to be present, at vary<strong>in</strong>g densities, on Corom<strong>and</strong>el Harbour mussel farmstructures <strong>and</strong> at Westhaven Mar<strong>in</strong>a year round (June 2011 to July 2012). The cycle of plant growth <strong>and</strong> density wasrelated to water temperature. Size <strong>and</strong> density of <strong>Undaria</strong> plants <strong>in</strong>creased steadily from June through until lateOctober/early November when plant lengths <strong>and</strong> the presence <strong>and</strong> volume of sporophylls peaked. This peak <strong>in</strong> plant size<strong>and</strong> reproductive maturity co<strong>in</strong>cided with water temperatures reach<strong>in</strong>g ~17ºC. Average length then showed a steadydecl<strong>in</strong>e, as the mature plants degraded, with the shortest average lengths recorded at Corom<strong>and</strong>el <strong>and</strong> at Westhaven <strong>in</strong>
late February when water temperatures peaked. In general the Hauraki Gulf temperatures recorded fall above theoptimum <strong>Undaria</strong> grow<strong>in</strong>g conditions from November to May but still rema<strong>in</strong> with<strong>in</strong> the known range for sub-optimal growth<strong>and</strong> reproduction. Individual plants did not live for an entire year but overlapp<strong>in</strong>g generations occur with a cont<strong>in</strong>ualrecruitment <strong>and</strong> replacement of <strong>in</strong>dividuals. <strong>Undaria</strong> follows a dist<strong>in</strong>ct pattern of rapid recruitment <strong>and</strong> growth dur<strong>in</strong>g thecooler months of w<strong>in</strong>ter-spr<strong>in</strong>g.Results <strong>in</strong>dicate that the warmer waters of the Hauraki Gulf may produce smaller plants with a slower growth rate thanthose found <strong>in</strong> cooler waters.The impact of <strong>Undaria</strong> on mussel farm<strong>in</strong>g activities <strong>and</strong> on native rocky reef flora <strong>and</strong> fauna has not been exam<strong>in</strong>ed <strong>in</strong> theHauraki Gulf. The dense populations of large plants seen at the WBMFZ <strong>and</strong> on the four other heavily <strong>in</strong>fested farmssurveyed could potentially have strong impacts on light availability, nutrient cycl<strong>in</strong>g <strong>and</strong> food availability for the musselsbe<strong>in</strong>g grown on these farms. It appears that careful <strong>and</strong> regular ma<strong>in</strong>tenance of exist<strong>in</strong>g mussel farms <strong>and</strong> associatedequipment will help towards mitigat<strong>in</strong>g these potential impacts as well as m<strong>in</strong>imis<strong>in</strong>g the spread of <strong>Undaria</strong> to coastalareas <strong>and</strong> new mar<strong>in</strong>e farms.It is apparent that <strong>in</strong>troduc<strong>in</strong>g mussel farm <strong>in</strong>frastructure to a site will likely result <strong>in</strong> the <strong>in</strong>troduction of <strong>Undaria</strong> that site. Ifmussel farms are to be placed <strong>in</strong> High Value Conservation sites or sites near mar<strong>in</strong>e reserves it must be taken <strong>in</strong>toconsideration that <strong>Undaria</strong> will then be <strong>in</strong>troduced to these sites. Coastal reef sites at risk of <strong>Undaria</strong> colonisation may bethose with impaired or reduced native algal canopies or abundant natural open spaces, on reefs or rocks, <strong>in</strong> the shallowsubtidal zone. We recommend that further monitor<strong>in</strong>g <strong>and</strong> research be carried out around the Corom<strong>and</strong>el region to moreaccurately ascerta<strong>in</strong> the extent of <strong>Undaria</strong> <strong>in</strong>festation around the Corom<strong>and</strong>el Coast <strong>and</strong> determ<strong>in</strong>e the factors <strong>in</strong>fluenc<strong>in</strong>gthe abundance of <strong>Undaria</strong> at mar<strong>in</strong>e farm<strong>in</strong>g <strong>and</strong> coastal sites. Annual monitor<strong>in</strong>g of <strong>Undaria</strong> populations could helpunderst<strong>and</strong> the spread of populations <strong>and</strong> the potential risks to coastal environments <strong>and</strong> native species.Two other <strong>in</strong>vasive species were prevalent on mussel farm structures. The clubbed tunicate Styela clava was found on allthe mussel farms surveyed <strong>and</strong> the green seaweed Codium fragile ssp. tomentosoides was present on twenty eight out ofthe thirty one farms surveyed. The Asian paddle crab Charybdis japonica was found at two coastal sites.2
2. Introduction<strong>Undaria</strong> p<strong>in</strong>natifida (Harvey) Sur<strong>in</strong>gar is a large lam<strong>in</strong>arian kelp. <strong>Undaria</strong> is an annual with several different life stages. Itwas <strong>in</strong>troduced to New Zeal<strong>and</strong> waters <strong>in</strong> the 1980’s by Asian fish<strong>in</strong>g vessels (Parsons, 1994; Verlaque, 2007). <strong>Undaria</strong> isknown to have direct negative impacts on <strong>in</strong>digenous biota <strong>and</strong> it can change the entire structure of mar<strong>in</strong>e ecosystems(M<strong>in</strong>istry of Fisheries [MoF], 2001; Neill, 2008; Stuart, 2004). A s<strong>in</strong>gle <strong>Undaria</strong> plant can produce one hundred millionzoospores (Akiyama <strong>and</strong> Kurogi, 1982), mean<strong>in</strong>g the establishment of a s<strong>in</strong>gle mature plant is enough to found a vigorousnew population (Hay <strong>and</strong> Luckens, 1987). <strong>Undaria</strong> grows rapidly <strong>in</strong> favourable conditions <strong>and</strong> can form densemono‐specific st<strong>and</strong>s, allow<strong>in</strong>g it to out‐compete native species (Russell et al, 2008; Verlaque, 2007). <strong>Undaria</strong> has thepotential to displace macroalgae (e.g. Carpophyllum mascalocarpum, <strong>and</strong> Cystophora species) <strong>and</strong> other native speciessuch as paua (Hay <strong>and</strong> Luckens, 1987; Hay, 1990; MoF, 2001; Stuart, 2004), alter habitat for commercial species such asmussels, disrupt aquaculture activities, <strong>and</strong> may affect the cultural values of some mar<strong>in</strong>e sites (Cecere et al, 2000;Henkel <strong>and</strong> Hofmann, 2008; MoF, 2001; Neill, 2008; Russell et al, 2008; S<strong>in</strong>ner et al, 2000; Verlaque, 2007). Although<strong>Undaria</strong> can survive <strong>and</strong> reproduce at temperatures between zero <strong>and</strong> thirty degrees Celsius (Floc’h et al, 1991), growthof <strong>Undaria</strong> sporophytes (hereafter called plants) is optimum at 15-17 °C with growth cont<strong>in</strong>u<strong>in</strong>g slowly to 20°C (Saito,1975).S<strong>in</strong>ce its detection <strong>in</strong> Well<strong>in</strong>gton <strong>in</strong> 1987 (Hay & Luckens, 1987) <strong>Undaria</strong> has spread rapidly around New Zeal<strong>and</strong> coasts.Vessel hulls <strong>and</strong> aquaculture equipment are known to be the ma<strong>in</strong> dispersal pathways (Hay, 1990; Neill, 2008; Russell etal, 2008; S<strong>in</strong>ner et al, 2000; Verlaque, 2007). <strong>Undaria</strong> is now widespread around most of New Zeal<strong>and</strong>’s eastern <strong>and</strong>southern coastl<strong>in</strong>es from Auckl<strong>and</strong> to Bluff (Neill, 2008; Russell et al, 2008; Verlaque, 2007).<strong>Undaria</strong> was first officially recorded, on mussel farm <strong>in</strong>frastructure, <strong>in</strong> the Firth of Thames <strong>in</strong> 2002 (Stuart, 2004). Musselfarmers report the presence of <strong>Undaria</strong> <strong>in</strong> the Firth of Thames s<strong>in</strong>ce 1999 (Jessop, 2006). It was officially recorded <strong>in</strong> theWaitemata Harbour at Hobson West mar<strong>in</strong>a, <strong>in</strong> 2004. A subsequent <strong>in</strong>vestigation <strong>in</strong>to the <strong>distribution</strong> <strong>and</strong> density of thispopulation by Stuart <strong>and</strong> McClary (2004) concluded <strong>Undaria</strong> had at that time been present <strong>in</strong> the Waitemata Harbour,<strong>in</strong>clud<strong>in</strong>g Westhaven Mar<strong>in</strong>a, for 3-4 years. Quantitative data on the extent <strong>and</strong> nature of <strong>Undaria</strong> populations <strong>in</strong> the widerHauraki Gulf <strong>in</strong>clud<strong>in</strong>g the Corom<strong>and</strong>el area are currently lack<strong>in</strong>g. The potential exists for this highly <strong>in</strong>vasive species tospread to regions regarded as hav<strong>in</strong>g high conservation values such as mar<strong>in</strong>e reserves <strong>and</strong> Hauraki Gulf Isl<strong>and</strong>s (MoF,2001; Neill, 2008). The impacts of <strong>Undaria</strong> are not well understood, but are expected to vary considerably depend<strong>in</strong>g onthe location (MAF, 2010; Parsons, 1994). Data on the <strong>distribution</strong> <strong>and</strong> biology of <strong>Undaria</strong> <strong>in</strong> the Hauraki Gulf is necessaryto determ<strong>in</strong>e the risks of future spread, the potential impact on environmental values <strong>and</strong> on mar<strong>in</strong>e farm<strong>in</strong>g, <strong>and</strong> <strong>in</strong>general to <strong>in</strong>form management decisions regard<strong>in</strong>g this <strong>in</strong>vasive species.The present study has two ma<strong>in</strong> objectives:1. Investigate the spatial <strong>distribution</strong> of <strong>Undaria</strong> populations <strong>and</strong> levels of <strong>in</strong>festation on mussel farms <strong>and</strong> adjacentcoastal sites around the Corom<strong>and</strong>el Pen<strong>in</strong>sula.2. Investigate <strong>seasonal</strong> <strong>variation</strong> <strong>in</strong> the structure <strong>and</strong> biology of <strong>Undaria</strong> populations at sites around the Corom<strong>and</strong>elPen<strong>in</strong>sula <strong>and</strong> at Westhaven Mar<strong>in</strong>a <strong>in</strong> the Waitemata Harbour. Sites at Corom<strong>and</strong>el <strong>and</strong> Westhaven weremonitored from June 2011 to July 2012.The first objective was <strong>in</strong>vestigated by carry<strong>in</strong>g out field surveys on mussel farms <strong>and</strong> areas of coast adjacent to musselfarms between November 2011 <strong>and</strong> February 2012 (Figure 1). The second objective was exam<strong>in</strong>ed with monthlymonitor<strong>in</strong>g of <strong>Undaria</strong> populations on two mussel farms <strong>in</strong> the Corom<strong>and</strong>el Harbour <strong>and</strong> fortnightly monitor<strong>in</strong>g atWesthaven Mar<strong>in</strong>a. Areas around the Corom<strong>and</strong>el with high boat traffic such as sw<strong>in</strong>g moor<strong>in</strong>g sites <strong>and</strong> boat ramps werealso surveyed <strong>in</strong> order to gather <strong>in</strong>formation around the potential mechanisms of spread of <strong>Undaria</strong>.3
4Figure 1: Ma<strong>in</strong> study locations for <strong>Undaria</strong> <strong>in</strong> the Hauraki Gulf. Red symbols <strong>in</strong>dicate monitor<strong>in</strong>g sites at Corom<strong>and</strong>elHarbour <strong>and</strong> Westhaven Mar<strong>in</strong>a. Yellow symbols <strong>in</strong>dicate areas where <strong>Undaria</strong> surveys were carried out <strong>in</strong>clud<strong>in</strong>g thelarge western Corom<strong>and</strong>el area (yellow box), which <strong>in</strong>cludes the Wilson Bay Mar<strong>in</strong>e Farm<strong>in</strong>g Zone.
3. Methods3.1. <strong>Spatial</strong> <strong>distribution</strong> surveyThe start<strong>in</strong>g po<strong>in</strong>t for this survey was mussel farm structures. Mussel farm locations were identified from Waikato RegionalCouncil survey maps <strong>and</strong> although not all <strong>in</strong>dividual mussel farms could be surveyed at least one farm at each geographicgroup<strong>in</strong>g of farms was <strong>in</strong>spected. The possible spread of <strong>Undaria</strong> from mussel farm <strong>in</strong>frastructure to adjacent coastal reefsystems was exam<strong>in</strong>ed by survey<strong>in</strong>g coastal sites adjacent to every mussel farm or group of mussel farms around theCorom<strong>and</strong>el Pen<strong>in</strong>sula. Mussel farms <strong>and</strong> adjacent reef habitats were accessed from the University of Auckl<strong>and</strong> researchvessel R.V. Hawere. A comb<strong>in</strong>ation of snorkell<strong>in</strong>g <strong>and</strong> div<strong>in</strong>g observations were used as required.Other “high risk” areas for <strong>Undaria</strong> colonisation are those frequented by recreational <strong>and</strong> commercial boat traffic (Hay <strong>and</strong>Luckens, 1987; Hay, 1990, Russell et al, 2007; Verlaque, 2007). Areas with high boat traffic such as sw<strong>in</strong>g moor<strong>in</strong>g sites<strong>and</strong> boat ramps were surveyed. In-water surveys were carried out at most sites. Some shore <strong>and</strong> kayak based <strong>in</strong>spectionswere also carried out..3.1.1. Mussel farm locationsThe mussel farms around the Corom<strong>and</strong>el Pen<strong>in</strong>sula were split <strong>in</strong>to twelve survey locations. Ten locations are on thewestern side of the Pen<strong>in</strong>sula <strong>and</strong> the other two are on the eastern coastl<strong>in</strong>e at Kennedy Bay <strong>and</strong> Port Charles (Figure 1).Survey locations comprised between one <strong>and</strong> seven mussel farms, except for the Wilson Bay Mar<strong>in</strong>e Farm<strong>in</strong>g Zone(WBMFZ) <strong>in</strong> the Firth of Thames which comprises more than 150 mussel farms <strong>in</strong> 1250ha of water approximately twokilometres offshore. Operational details <strong>and</strong> site maps for the eleven smaller locations were supplied by the WaikatoRegional Council. A site map of the WBMFZ was supplied by the Sealord Mar<strong>in</strong>e Farms manager. These details wereused to contact mussel farm owners <strong>and</strong>/or operators to ensure access was approved before visit<strong>in</strong>g farms. Some farmscould not be accessed due to operational reasons. Of the 53 <strong>in</strong>dividual mussel farms listed at the eleven smaller locationsa total of 24 farms were surveyed. Seven representative farms were surveyed with<strong>in</strong> the WBMFZ.For each farm surveyed the outermost l<strong>in</strong>es at each end of the mussel farm <strong>and</strong> a selection of <strong>in</strong>ner l<strong>in</strong>es were assessed.Mussel farm size was typically ten to sixteen l<strong>in</strong>es <strong>and</strong> at least three l<strong>in</strong>es at every farm were surveyed. The numbers ofmussel l<strong>in</strong>es surveyed at each farm was generally relative to the total number <strong>and</strong> size of l<strong>in</strong>es present. However, somefarms were surveyed less thoroughly than others due to poor weather conditions <strong>and</strong> some farms did not have l<strong>in</strong>es <strong>in</strong> thewater at the time of survey<strong>in</strong>g. Farms with bare l<strong>in</strong>es were not surveyed.Surveys of l<strong>in</strong>es were conducted on snorkel <strong>and</strong>/or SCUBA. Effort was concentrated near the surface as the vertical<strong>distribution</strong> of <strong>Undaria</strong> has been found to be mostly at the surface layers on artificial structures such as mar<strong>in</strong>e farms(Chen, 2012; Duder, 2009; Hay <strong>and</strong> Luckens, 1987; Hay <strong>and</strong> Villouta, 1993; Jessop, 2006). At each farm surveyors swamthe length of each designated mussel l<strong>in</strong>e, on or near the surface, not<strong>in</strong>g the presence <strong>and</strong> density of <strong>Undaria</strong> per fiftymetre length of mussel l<strong>in</strong>e. Most mussel l<strong>in</strong>es were approximately 100m long so comprised two transects each. A total of268 transects were run along 132 mussel l<strong>in</strong>es at 31 different mussel farms. Notes were taken on the size <strong>distribution</strong> <strong>and</strong>reproductive status of the <strong>Undaria</strong> surveyed at each l<strong>in</strong>e. The presence of other <strong>in</strong>vasive species was also noted.Representative photographs were taken of <strong>Undaria</strong> <strong>and</strong>/or other <strong>in</strong>vasive species present. A m<strong>in</strong>imum of five musselswere measured on every l<strong>in</strong>e surveyed <strong>and</strong> the average mussel size was calculated for each of these l<strong>in</strong>es.Surveys of farms were carried out between November 22 nd 2011 <strong>and</strong> February 3 rd 2012. To exam<strong>in</strong>e the potential fordifferences <strong>in</strong> tim<strong>in</strong>g of surveys to <strong>in</strong>fluence the presence or <strong>in</strong>festation level of <strong>Undaria</strong> some farms were visited on bothNovember <strong>and</strong> February sampl<strong>in</strong>g trips.5
3.1.2. Coastal reef locationsContiguous 50 x 10m transects were run along sections of coast adjacent to all mussel farm locations on the Corom<strong>and</strong>elPen<strong>in</strong>sula. A total of twenty six coastal reef areas were surveyed via SCUBA <strong>and</strong>/or snorkel. In New Zeal<strong>and</strong>, <strong>Undaria</strong>populations that occur on native reef habitats are typically densest from the low <strong>in</strong>tertidal fr<strong>in</strong>ge down to approximatelythree metres (Brown <strong>and</strong> Lamare, 1994; Parsons, 1994; S<strong>in</strong>ner et al, 2000; Stuart, 2004; Russell et al, 2007). Much of thereef adjacent to the farms <strong>in</strong> the western Corom<strong>and</strong>el is relatively shallow, with a s<strong>and</strong>-reef border at depths of less than5m <strong>and</strong> a limited offshore extent of 15-30m. Sampl<strong>in</strong>g was concentrated on the shallow-subtidal marg<strong>in</strong> of the reef,typically just below the low-tide mark. The depth of the surveys conducted ranged from one to five metres, depend<strong>in</strong>g onhabitat <strong>and</strong> tide levels, with an average depth across the total 244 transects of 2.4m. In the case of the WBMFZ, wherethere is more than five kilometres of adjacent coastl<strong>in</strong>e, five coastal sites were selected where subtidal reef habitatoccurred that could potentially be colonised by <strong>Undaria</strong>. A total of 2250 meters of this adjacent coast was surveyed. Thenature of the benthic environment <strong>and</strong> algal species present was recorded for each 50m transect. The presence of other<strong>in</strong>vasive species was noted.Surveys were carried out between November 22 nd 2011 <strong>and</strong> February 3 rd 2012. To exam<strong>in</strong>e the potential for differences <strong>in</strong>tim<strong>in</strong>g of surveys to <strong>in</strong>fluence the presence or <strong>in</strong>festation level of <strong>Undaria</strong> two sites where <strong>Undaria</strong> was recorded <strong>in</strong>November were revisited <strong>in</strong> February <strong>and</strong> <strong>Undaria</strong> populations were qualitatively compared.3.1.3. Other “high risk” locationsIn order to <strong>in</strong>vestigate the potential spread of <strong>Undaria</strong> by recreational vessels, seven “high risk” sites of <strong>in</strong>terest weresurveyed <strong>in</strong> February 2012. These were comprised of two sw<strong>in</strong>g moor<strong>in</strong>g sites <strong>in</strong> the Corom<strong>and</strong>el Harbour at Takawharebay <strong>and</strong> W<strong>in</strong>dy Po<strong>in</strong>t/Puhi Rare, three boat ramps; Waikawau (Thames coast), Port Charles <strong>and</strong> the Sugarloafrecreational <strong>and</strong> mussel load<strong>in</strong>g ramp at Te Kouma, a set of moor<strong>in</strong>g buoys <strong>in</strong> Kennedy bay <strong>and</strong> the <strong>in</strong>frastructure atHannaford’s Jetty <strong>in</strong> the Corom<strong>and</strong>el Harbour were also surveyed. Boat ramp sites were surveyed via snorkel <strong>and</strong>/orSCUBA, surveyors searched artificial structures <strong>and</strong> surround<strong>in</strong>g coastal reef sites. The sw<strong>in</strong>g moor<strong>in</strong>g site at W<strong>in</strong>dyPo<strong>in</strong>t/Puhe Rare was surveyed via SCUBA, divers <strong>in</strong>spected a r<strong>and</strong>om subset of moor<strong>in</strong>gs <strong>and</strong> mussel barge hulls. Therecreational sw<strong>in</strong>g moor<strong>in</strong>gs at Takawhare Bay were surveyed from kayaks, a r<strong>and</strong>om subset of moor<strong>in</strong>g floats/l<strong>in</strong>es <strong>and</strong>vessel hulls were <strong>in</strong>spected from the surface or moor<strong>in</strong>g floats were lifted out of the water <strong>and</strong> <strong>in</strong>spected aboard thekayaks. The moor<strong>in</strong>g buoys at Kennedy bay were <strong>in</strong>spected <strong>in</strong> a similar manner, by lift<strong>in</strong>g them aboard a d<strong>in</strong>ghy. AtTakawhare Bay 43 out of 120 listed moor<strong>in</strong>gs were surveyed. At Puhi Rare 12 out of the seventy listed moor<strong>in</strong>gs were<strong>in</strong>spected, very poor visibility prevented more <strong>in</strong>spections at this site.3.1.4. Semi-quantitative measurements of <strong>Undaria</strong> abundanceFor each 50m section of mussel l<strong>in</strong>e or coast surveyed the number of <strong>Undaria</strong> plants sighted was placed <strong>in</strong> one of fivecategories, these are shown <strong>in</strong> Table 1:Table 1: <strong>Undaria</strong> <strong>in</strong>festation categoriesCategory Number of plants per 50m Level of Infestation0 0 None (green)1 1-10 Low (orange)2 11-100 Medium (orange)3 101-500 High (red)4 >500 Heavily <strong>in</strong>fested (red)6
For mapp<strong>in</strong>g purposes the <strong>Undaria</strong> categories were used to create colour coded levels of <strong>in</strong>festation (Table 1). Numbersare for <strong>Undaria</strong> plants per 50 of mussel l<strong>in</strong>e or coast surveyed: Green = no <strong>Undaria</strong> observed. Orange = 1-100 <strong>Undaria</strong>plants recorded. Red = >100 <strong>Undaria</strong> plants recorded.3.1.5. Other <strong>in</strong>vasive speciesDirect surveyor observations as well as underwater photographs <strong>and</strong> some video records were taken at each site <strong>and</strong>used to assess the presence or absence of thirteen <strong>in</strong>vasive species (<strong>in</strong> addition to <strong>Undaria</strong>): Ascidiella aspersa (tunicate),Bugula nerit<strong>in</strong>a (bryozoan), Caulerpa taxifolia (alga), Charybdis japonica (crustacean), Ciona <strong>in</strong>test<strong>in</strong>alis (bryozoan),Codium fragile ssp. tomentosoides (alga), Musculista senhousia (mollusc), Polysiphonia brodiei (alga), Sabellaspallanzanii (annelid), Schizoporella errata (bryozoan), Tubastraea cocc<strong>in</strong>ea (coral) <strong>and</strong> Watersipora subtorquata(bryozoan).7
3.2. Seasonal monitor<strong>in</strong>g of <strong>Undaria</strong> populationsTo <strong>in</strong>vestigate the phenology of <strong>Undaria</strong> populations <strong>in</strong> the Hauraki Gulf monitor<strong>in</strong>g sites were set up <strong>in</strong> June 2011 onmussel farms <strong>in</strong> the Corom<strong>and</strong>el Harbour (Figure 2) <strong>and</strong> on the pontoons at Westhaven Mar<strong>in</strong>a <strong>in</strong> Auckl<strong>and</strong> (Figure 3).Due to the different nature of these habitats the sampl<strong>in</strong>g methods used varied between these sites.3.2.1. Corom<strong>and</strong>el monitor<strong>in</strong>gThe monitor<strong>in</strong>g site with<strong>in</strong> Corom<strong>and</strong>el Harbour is located on two adjacent mussel farms (Figure 2). Mussels grown at thissite are on the l<strong>in</strong>es for approximately n<strong>in</strong>e to twelve months, until mussels reach a size of 95-100mm when they areprocessed. After harvest<strong>in</strong>g the floats are cleaned before re-deploy<strong>in</strong>g them – <strong>and</strong> they usually go back to the same site(Peter James, pers comm., 11/7/2011). Monitor<strong>in</strong>g consists of boat based snorkell<strong>in</strong>g along mussel l<strong>in</strong>es. At both of thedesignated mussel farms, two mussel l<strong>in</strong>es were chosen at r<strong>and</strong>om for <strong>in</strong>spection <strong>in</strong> June 2011. These l<strong>in</strong>es weresurveyed each month until the mussels were harvested. The harvest<strong>in</strong>g process removes <strong>Undaria</strong> from the floats. So,when l<strong>in</strong>es surveyed the previous month have been harvested, surveillance shifts to the nearest parallel l<strong>in</strong>es with musselspresent. Inspection occurs along the first ten mussel floats along the four designated mussel l<strong>in</strong>es. All <strong>Undaria</strong> present onthe mussel floats is counted <strong>and</strong> measured. Measurements are taken of the total length of the plants <strong>and</strong> the length <strong>and</strong>width of the reproductive tissue at the base of the plant, the sporophyll (if present). The submerged area of the float isapproximately 1m by 1.2m. Consequently, densities are expressed on a mˉ2 basis. Data from both sites will be comb<strong>in</strong>ed<strong>in</strong> this report. Representative photographs of <strong>Undaria</strong> are taken at each visit.Figure 2: Corom<strong>and</strong>el Harbour monitor<strong>in</strong>g sites8
3.2.2. Westhaven monitor<strong>in</strong>gWesthaven Mar<strong>in</strong>a was chosen as a study site <strong>in</strong> the Waitemata harbour as it provides an easily accessible <strong>Undaria</strong>population to the University of Auckl<strong>and</strong>. <strong>Undaria</strong> grows from the pontoons of the Mar<strong>in</strong>a. Surveys are pier based counts<strong>and</strong> measurements. Surveys have been conducted fortnightly at Pier Z <strong>and</strong> Pier W (Figure 3) s<strong>in</strong>ce July 2011. Data fromboth piers will be comb<strong>in</strong>ed <strong>in</strong> this report.Figure 3: Westhaven Mar<strong>in</strong>a monitor<strong>in</strong>g sitesPier WPier ZSurvey sites are at the ends of Pier Z <strong>and</strong> Pier W <strong>and</strong> consist of approximately 75m <strong>and</strong> 45m of concrete pontoon edgerespectively. Surveys are carried out fortnightly. At both pier Z <strong>and</strong> Pier W. Measurements are taken of the total plantlength <strong>and</strong> length <strong>and</strong> width of the sporophyll (if present) for forty r<strong>and</strong>om plants per survey visit. Once a month 24 r<strong>and</strong>omone metre sections of pontoon at pier Z <strong>and</strong> 12 r<strong>and</strong>om one metre sections at pier W are <strong>in</strong>spected <strong>and</strong> all <strong>Undaria</strong> plantsto a depth of approximately 0.3m <strong>in</strong> each one metre section are counted (<strong>Undaria</strong> is typically only found <strong>in</strong> this depthrange on the pontoons). Counts are expressed on a mˉ2 basis.Twenty plants at each pier were tagged <strong>in</strong> July 2011, us<strong>in</strong>g a cable tie placed around the base of the stipe, <strong>and</strong> growthrate was monitored. Each fortnight a 5mm diameter hole was punched beside the midrib of each plant, 100mm above theblade/stipe junction <strong>and</strong> beyond the meristematic region (Stuart, 1999). The lateral displacement of the hole relative to theblade/stipe junction was then measured every two weeks to determ<strong>in</strong>e growth rate. This hole-punch technique isnecessary due to the dis<strong>in</strong>tegration of the blade which occurs early <strong>in</strong> the life cycle of <strong>Undaria</strong> (Castric-Fey, 1999).Representative photographs of <strong>Undaria</strong> are taken at each visit.3.3. Environmental dataEach time a monitor<strong>in</strong>g or survey site was visited record<strong>in</strong>gs were made of sal<strong>in</strong>ity us<strong>in</strong>g a Eutech Salt 6+ sal<strong>in</strong>ity meter<strong>and</strong> three surface water samples were taken <strong>in</strong> order to determ<strong>in</strong>e nitrate, nitrite, ammonium <strong>and</strong> phosphate levels.Temperature is logged at each monitor<strong>in</strong>g site via a HOBO© temperature logger, a pendant suspended <strong>in</strong> the waterapproximately 1 m below the surface <strong>and</strong> set to log temperature every thirty m<strong>in</strong>utes 24 hrs a day. Secchi depth wasmeasured at each mussel farm <strong>in</strong> the spatial <strong>distribution</strong> survey with a st<strong>and</strong>ard 30 cm diameter secchi disk.9
4. Results4.1. <strong>Spatial</strong> <strong>distribution</strong> survey4.1.1. Coastal surveyThe <strong>in</strong>festation levels of <strong>Undaria</strong> at coastal locations surveyed on the western Corom<strong>and</strong>el Pen<strong>in</strong>sula are mapped <strong>in</strong>Figure 4. <strong>Undaria</strong> was found at five out of the twenty six coastal reef sites surveyed from R.V. Hawere <strong>and</strong> one sitesurveyed separately from the shore (Waitataramoa bay). More detailed maps show<strong>in</strong>g all sites <strong>in</strong>clud<strong>in</strong>g Kennedy Bay <strong>and</strong>Port Charles are shown <strong>in</strong> Appendix 1. Descriptions of the sites where <strong>Undaria</strong> was found are given <strong>in</strong> Table 2 <strong>and</strong><strong>in</strong>formation on all sites surveyed is summarised <strong>in</strong> Appendix 2.Table 2: Summary of coastal sites where <strong>Undaria</strong> was observedDate29/7/2011LocationWaitataramoabay *GPSCo-ord<strong>in</strong>ates36º 48’ 27 S175º 27’ 41 ENumber of<strong>Undaria</strong>plants6<strong>Undaria</strong> SubstrateRocky reef edge at<strong>in</strong>ter-tidal/subtidalboundary. Mediumboulders.Surround<strong>in</strong>g Habitat DescriptionRocky reef shelf with bare rock,Homosira banksii <strong>and</strong> patches ofcorall<strong>in</strong>e turf. Medium boulderswith sparse Ecklonia radiata.6/12/2011 Wilson Bay7/12/20117/12/2011Corom<strong>and</strong>elHarbourManaiaHarbour(WekaruaIsl<strong>and</strong>)36º 53’ 24 S175º 25’ 35 E36º 48‘ 27 S175º 27’ 11 E36º 50’ 30 S175º 25’ 17 E253Small boulders <strong>and</strong>pebble patches.Inside edge of reefon rocks border<strong>in</strong>gs<strong>and</strong> flats.Small boulders <strong>in</strong>open spaces <strong>in</strong>sidekelp b<strong>and</strong>.Mixed algae on boulders. Ma<strong>in</strong>lyEcklonia radiata withCarpophyllum flexuosum <strong>and</strong>some Carpophyllum plumosum.S<strong>and</strong> patches.Rocky boulder reef, mixed algae-Ecklonia radiata, Carpophyllummaschalocarpum, Carpophyllumflexuosum.Small boulders <strong>and</strong> lots of openreef Low density algae -Carpophyllum flexuosum <strong>and</strong>Ecklonia radiata.7/12/2011<strong>and</strong>3/2/2012Kirita bay36º 51’ 49 S175º 24’ 41 E49Corall<strong>in</strong>e flats <strong>and</strong>on mediumboulders betweens<strong>and</strong> flats.Low density mixed algal canopies–Ecklonia radiata, Carpophyllummaschalocarpum (dom<strong>in</strong>ant),Carpophyllum plumosum.2/02/2012MotukopakeIsl<strong>and</strong>36º 45’ 16 S175º 25’ 11 E2 Small boulders.Small boulders with sparseSargassum s<strong>in</strong>clairii <strong>and</strong>Carpophyllum flexuosum*These plants were discovered outside the official survey dur<strong>in</strong>g a separate site <strong>in</strong>spection from the shore.10
Figure 4: Western Corom<strong>and</strong>el Pen<strong>in</strong>sula coastal survey sites: Green paths <strong>in</strong>dicate no <strong>Undaria</strong> was sighted<strong>and</strong> orange represents sites where <strong>Undaria</strong> plants were present.<strong>Undaria</strong> was found <strong>in</strong> shallow reef habitats with easily colonisable open spaces, it was not found to be present atcomparable sites with dense algal canopies. Plants were seen to be colonis<strong>in</strong>g areas of small to medium boulders orpatches of clear rocky reef <strong>in</strong>side the subtidal algal belt or adjacent to it (low-<strong>in</strong>tertidal or reef-s<strong>and</strong> border). Infestationlevels were low (Category 1) at five of the coastal sites. Between two <strong>and</strong> six plants were recorded at these five sites, ateach site the <strong>Undaria</strong> seen was clustered with<strong>in</strong> one 50m transect only. A medium level of <strong>in</strong>festation (Category 2) wasseen at Kirita Bay where forty-n<strong>in</strong>e plants were counted. This site comprised a relatively large area (~30 x 30m) ofrelatively flat reef at ~mean low water that was dom<strong>in</strong>ated by corall<strong>in</strong>e turf (Corall<strong>in</strong>a offic<strong>in</strong>alis). A sparse mixed algalassemblage, compris<strong>in</strong>g Ecklonia radiata, Carpophyllum maschalocarpum (dom<strong>in</strong>ant) <strong>and</strong> Carpophyllum plumosum,occurred <strong>in</strong> a marg<strong>in</strong>al subtidal fr<strong>in</strong>ge <strong>and</strong> s<strong>and</strong> occurred at about one meter depth.11
The low densities <strong>and</strong> <strong>in</strong>festation levels of <strong>Undaria</strong> at coastal sites may have been <strong>in</strong>fluenced by the tim<strong>in</strong>g of surveys,with n<strong>in</strong>e sites hav<strong>in</strong>g been surveyed <strong>in</strong> February when temperatures were warmest <strong>and</strong> <strong>Undaria</strong> is typically at its lowestdensities (see Section 4.2). However, to <strong>in</strong>vestigate the potential for <strong>seasonal</strong> <strong>variation</strong> to have <strong>in</strong>fluenced our results werevisited the Kirita site (mentioned above), where <strong>Undaria</strong> was reported <strong>in</strong> the November surveys, <strong>in</strong> February. All lifestages of <strong>Undaria</strong> were seen grow<strong>in</strong>g here both the site visits carried out on the 7/12/2011 <strong>and</strong> 3/2/2012 (Figures 5A <strong>and</strong>5B). <strong>Undaria</strong> rema<strong>in</strong>ed prevalent on the mussel farms dur<strong>in</strong>g February surveys, if only as large degraded sporophylls atsome sites.Figure 5: <strong>Undaria</strong> plantlets <strong>in</strong> corall<strong>in</strong>e turf dom<strong>in</strong>ated habitat <strong>in</strong> the low <strong>in</strong>tertidal zone (A) <strong>and</strong>mature <strong>Undaria</strong> sporophyte on the reef-s<strong>and</strong> border (~1m depth) (B). Kirita Bay, 3/2/12.AB12
4.1.2. Mussel farm survey<strong>Undaria</strong> was recorded at all of the mussel farms surveyed on the western Corom<strong>and</strong>el Pen<strong>in</strong>sula (Figure 6). No <strong>Undaria</strong>was seen on the two mussel farms surveyed at Kennedy Bay <strong>and</strong> one of the farms surveyed at Port Charles. Moredetailed maps are shown <strong>in</strong> Appendix 1. The highest <strong>in</strong>festation levels were recorded at all Wilson Bay farms (>500 plantsper 50m transect; Figure 7B), followed by three farms off Motukopake Isl<strong>and</strong>, Figure 7A, <strong>and</strong> one farm off WhanganuiIsl<strong>and</strong> (>100 plants per 50m transect). Levels of <strong>Undaria</strong> <strong>in</strong>festation were def<strong>in</strong>ed as low to medium (1-100 plants per 50mtransect) on seventeen mussel farms, high (>100 plants per 50m transect) on eleven mussel farms <strong>and</strong> zero on threemussel farms. A trend of decreas<strong>in</strong>g density of plants with <strong>in</strong>creas<strong>in</strong>g depth was observed (Figure 7A). Although depthprofiles were not taken at all sites, <strong>Undaria</strong> was generally seen to be most prevalent <strong>in</strong> the top two metres of water at allmussel farms. Plants were seen grow<strong>in</strong>g down to a depth of six metres at some sites (e.g. Motukopake <strong>and</strong> Wilson Bay).Figure 6: Western Corom<strong>and</strong>el Pen<strong>in</strong>sula mussel farm survey locations: Orange paths <strong>in</strong>dicate a mediumlevel of <strong>Undaria</strong> <strong>in</strong>festation <strong>and</strong> red represents sites where <strong>Undaria</strong> <strong>in</strong>festation levels were high. See Appendix 1for detailed maps <strong>and</strong> maps for Port Charles <strong>and</strong> Kennedy Bay.13
Figure 7: Heavily <strong>in</strong>fested mussel l<strong>in</strong>es, Motukopake Isl<strong>and</strong>, 23/11/12 (A) <strong>and</strong> Wilson Bay,6/12/11 (B).ABLevels of <strong>Undaria</strong> <strong>in</strong>festation were weakly positively related to the size of mussels. Mussel size is a general <strong>in</strong>dicator ofhow long the l<strong>in</strong>es have been <strong>in</strong> the water <strong>and</strong> can vary between <strong>in</strong>dividual l<strong>in</strong>es with<strong>in</strong> the same mussel farm. The highest<strong>Undaria</strong> <strong>in</strong>festation levels were generally seen on mussel l<strong>in</strong>es with mussels larger than 50-60mm (Figure 8), which wouldhave been <strong>in</strong> the water for at least 5-7 months.14
Figure 8: Mussel length <strong>and</strong> <strong>Undaria</strong> <strong>in</strong>festation4.1.3. “High risk” sitesHigh risk survey site results are summarised <strong>in</strong> Table 3 <strong>and</strong> are mapped <strong>in</strong> Appendix 1. No <strong>Undaria</strong> was found at themussel load<strong>in</strong>g facility/public boat ramp at Te Kouma, the sw<strong>in</strong>g moor<strong>in</strong>g sites at W<strong>in</strong>dy po<strong>in</strong>t/Puhe Rare <strong>and</strong> TakawhareBay, Hannaford’s jetty or the two other boat ramp sites surveyed <strong>in</strong> February 2012. A medium level of <strong>in</strong>festation(Category 2) was found on a s<strong>in</strong>gle moor<strong>in</strong>g float <strong>and</strong> l<strong>in</strong>e <strong>in</strong>spected at Kennedy Bay <strong>in</strong> February 2012.Table 3: “High risk” survey sitesDate Location Site <strong>Undaria</strong> plants sighted1/2/2012 Port CharlesPublic boat ramp <strong>and</strong>benthic surrounds.01/2/2012 Kennedy Bay Sw<strong>in</strong>g moor<strong>in</strong>gs.30 mature <strong>and</strong> degrad<strong>in</strong>g plants on as<strong>in</strong>gle moor<strong>in</strong>g buoy <strong>and</strong> l<strong>in</strong>e.3/2/2012Waikawau (Thames Public boat ramp <strong>and</strong>Coast)benthic surrounds.03/2/2012W<strong>in</strong>dy Po<strong>in</strong>t/Puhe Mussel barge sw<strong>in</strong>gRaremoor<strong>in</strong>gs <strong>and</strong> barge hulls.0Mussel barge load<strong>in</strong>g3/2/2012 Te Kouma/ Sugar Loaf facility/boat ramp <strong>and</strong>benthic surrounds.06/2/2012 Takawhare Bay Public sw<strong>in</strong>g moor<strong>in</strong>gs. 06/2/2012 Hannaford’s JettyPublic jetty <strong>and</strong> benthicsurrounds.015
4.1.4. Other Invasive SpeciesOther <strong>in</strong>vasive species recorded dur<strong>in</strong>g coastal surveys are shown <strong>in</strong> Appendix 2. The <strong>in</strong>vasive tunicate Styela Clava wasrecorded at ten of the twenty six coastal sites surveyed. The <strong>in</strong>vasive alga Codium fragile ssp. tomentosoides wasrecorded at two coastal sites <strong>and</strong> the Asian paddle crab Charybdis japonica was also seen two coastal sites. Results for<strong>in</strong>vasive species recorded on mussel farms are shown <strong>in</strong> Appendix 3A. All the mussel farms surveyed had Styela Clavagrow<strong>in</strong>g on the l<strong>in</strong>es <strong>and</strong>/or <strong>in</strong>frastructure. Twenty eight of the thirty one mussel farms surveyed had Codium fragile ssp.tomentosoides present. Styela Clava <strong>and</strong> Codium fragile ssp. tomentosoides were abundant on the moor<strong>in</strong>g l<strong>in</strong>es atTakawhare Bay. Styela Clava, Codium fragile ssp. tomentosoides <strong>and</strong> Charybdis japonica were recorded at the Waikawauboat ramp site <strong>and</strong> at Kirita Bay.4.1.5. Environmental DataSite environmental <strong>in</strong>formation for the spatial survey is shown <strong>in</strong> Appendix 3B. Dur<strong>in</strong>g this survey average sal<strong>in</strong>ityrecorded at mussel farm sites was 34.7 ppt with a range of only two parts per thous<strong>and</strong> recorded across all sites,maximum 35.5 ppt, <strong>and</strong> m<strong>in</strong>imum 33.5 ppt. The average temperature recorded over the survey was 18.7ºC with am<strong>in</strong>imum of 16ºC <strong>and</strong> a maximum of 20.6ºC. Temperatures were measured at different times of day <strong>and</strong> <strong>in</strong> vary<strong>in</strong>gweather conditions so cannot be directly compared between sites. Secchi depths are shown (from northern (left), tosouthern (right) locations) <strong>in</strong> Figure 9. Sites had an average secchi depth of 5.9m across all mussel farm sites with amaximum of 8.5 recorded at Wilson Bay <strong>and</strong> a m<strong>in</strong>imum of 4m at Koputauaki Bay.Figure 9: Secchi depths: <strong>Spatial</strong> survey locationsSeawater nutrient data is shown <strong>in</strong> Figure 10. Very high ammonia read<strong>in</strong>gs seen at Port Charles, Motorua Isl<strong>and</strong>,Koputauaki Bay, Motukopaki Isl<strong>and</strong>, Motukakarikitahi Isl<strong>and</strong> <strong>and</strong> Whanganui Isl<strong>and</strong> were all samples taken <strong>in</strong> November.Differences <strong>in</strong> ammonia levels at the same site can be seen for Port Charles, Motukopaki East <strong>and</strong> Kirita Bay as they wereeach visited <strong>in</strong> November, visit 1 <strong>and</strong> February, visit 2. Nitrite <strong>and</strong> nitrate were relatively variable among sites, with thehighest concentrations recorded <strong>in</strong> Port Charles <strong>and</strong> Manaia Harbour, as well as at one site at Motukopake Isl<strong>and</strong>.Nitrogen concentrations were typically low at the Wilson Bay farm sites. Phosphate occurred at relatively constantconcentrations among sites <strong>and</strong> times. For details on sampl<strong>in</strong>g dates <strong>and</strong> sites see Appendix 3B.16
Figure 10: Seawater nutrient data: <strong>Spatial</strong> survey locations4.2. Seasonal monitor<strong>in</strong>g of <strong>Undaria</strong> populations4.2.1 Environmental <strong>variation</strong> at monitor<strong>in</strong>g sitesOverall, seawater nutrient concentrations were similar between the Corom<strong>and</strong>el <strong>and</strong> Westhaven monitor<strong>in</strong>g sites (Figure11). Nitrate <strong>and</strong> nitrite tend to be highest <strong>in</strong> w<strong>in</strong>ter, whereas ammonia is generally higher but highly variable over thesummer months (from November onwards). Phosphate is relatively stable through time <strong>and</strong> similar between sites.Figure 11: Seawater nutrient data at <strong>Undaria</strong> monitor<strong>in</strong>g sites: Westhaven Mar<strong>in</strong>a (A) <strong>and</strong> Corom<strong>and</strong>el (B).A17
BTemperature data recorded at Corom<strong>and</strong>el <strong>and</strong> Westhaven sites is shown <strong>in</strong> Figure 12. Monitor<strong>in</strong>g of <strong>Undaria</strong> populationsbegan <strong>in</strong> June 2011 when the average monthly temperatures were 13.4˚C <strong>and</strong> 12.8˚C at Corom<strong>and</strong>el <strong>and</strong> WesthavenMar<strong>in</strong>a respectively. Temperature then <strong>in</strong>creased through until February with average monthly temperatures of 24˚C atWesthaven <strong>and</strong> 23˚C at Corom<strong>and</strong>el. From the end of February temperatures began to drop rapidly, there is a monthlyaverage <strong>in</strong> May of 16˚C at both Westhaven Mar<strong>in</strong>a <strong>and</strong> Corom<strong>and</strong>el as temperatures head down towards 12 ˚C <strong>in</strong> June2012.Figure 12: Average daily water temperature. Note: Corom<strong>and</strong>el temperature loggers were stolen from the monitor<strong>in</strong>gsite three times dur<strong>in</strong>g the study <strong>and</strong> hence data from this site is miss<strong>in</strong>g for some months.18
4.2.2 Temporal <strong>distribution</strong> <strong>and</strong> population dynamics of <strong>Undaria</strong> populationsPlant densities were much higher on a per meter square basis at Westhaven Mar<strong>in</strong>a compared to on mussel floats at theCorom<strong>and</strong>el study site (Figure 13). Plant densities were highly variable among floats at Corom<strong>and</strong>el but generally followedthe same temporal pattern as Westhaven Mar<strong>in</strong>a, with an <strong>in</strong>crease from June through until November, followed by largedecl<strong>in</strong>es, down to near zero, at both locations between December <strong>and</strong> February. Densities at the Corom<strong>and</strong>el site beganto <strong>in</strong>crease aga<strong>in</strong> <strong>in</strong> April 2012.Figure 13: Average plant density at Westhaven Mar<strong>in</strong>a (A) <strong>and</strong> Corom<strong>and</strong>el (B). Error bars are ± one st<strong>and</strong>ard error.ABThe percentage of plants with reproductive tissue, sporophylls, is shown <strong>in</strong> Figure 14A <strong>and</strong> the average sporophyll volumeis shown <strong>in</strong> Figure 14B. Both sites had maximal reproductive plant numbers between early November <strong>and</strong> late December2011. At Westhaven Mar<strong>in</strong>a, 95% of the plants measured had sporophylls by late December, whereas at Corom<strong>and</strong>el a19
maximum of 52% of the plants measured had sporophylls at any one time. The numbers of plants with sporophylls presentat both sites collapsed from early January. No plants with sporophylls were recorded at either site <strong>in</strong> March 2012.Sporophyll volume peaked between early November <strong>and</strong> mid-December at both Westhaven Mar<strong>in</strong>a <strong>and</strong> Corom<strong>and</strong>el.Figure 14: Reproductive status of <strong>Undaria</strong> populations. Percentage of reproductive plants with sporophylls (A) <strong>and</strong>Average Sporophyll Volume (B). Error bars are ± one st<strong>and</strong>ard error.ABAverage plant length <strong>in</strong>creased steadily from June 2011 <strong>and</strong> peaked dur<strong>in</strong>g October at Westhaven Mar<strong>in</strong>a <strong>and</strong> atCorom<strong>and</strong>el (Figure 15). The largest <strong>in</strong>dividual plants were recorded <strong>in</strong> October, with maximum sizes of 102 cm atWesthaven <strong>and</strong> 120 cm at Corom<strong>and</strong>el. Average length shows a steady decl<strong>in</strong>e from October as plants decay from theapex. Although no plants were seen <strong>in</strong> the survey area <strong>in</strong> Corom<strong>and</strong>el <strong>in</strong> February <strong>Undaria</strong> was seen on surround<strong>in</strong>g<strong>in</strong>frastructure. A gradual <strong>in</strong>crease <strong>in</strong> plant length is evident from February to April 2012 as new recruits appear.20
Figure 15: Average plant length at Westhaven Mar<strong>in</strong>a <strong>and</strong> Corom<strong>and</strong>el. Error bars are ± one st<strong>and</strong>ard error.Average growth rate of <strong>Undaria</strong> plants at Westhaven is shown <strong>in</strong> figure 16. The average growth rate peaked dur<strong>in</strong>g August2011 at 0.59cm dayˉ¹. Growth rate then decl<strong>in</strong>ed steadily down to 0.28cm dayˉ¹ <strong>in</strong> November. All tagged plants had thendied <strong>and</strong> were no longer present by December 2011.Figure 16: Average growth rate at Westhaven Mar<strong>in</strong>a. Error bars are ± one st<strong>and</strong>ard error.Note: growth was only recorded at Westhaven <strong>and</strong> from July to November 2011 as tagged plants were all gone byNovember 2011.Size frequency graphs show<strong>in</strong>g plant sizes at Westhaven Mar<strong>in</strong>a <strong>and</strong> Corom<strong>and</strong>el are shown <strong>in</strong> Appendix 4. Plantlets(
The sharp decl<strong>in</strong>e <strong>in</strong> the size <strong>and</strong> abundance of <strong>Undaria</strong> plants at Westhaven Mar<strong>in</strong>a between October 2011 <strong>and</strong> January2012 can be seen <strong>in</strong> Figure 17.Figure 17: <strong>Undaria</strong> plants at Pier Z Westhaven Mar<strong>in</strong>a21/10/11 6/01/1122
5. Discussion5.1. <strong>Spatial</strong> <strong>distribution</strong> of <strong>Undaria</strong> around the Corom<strong>and</strong>el Pen<strong>in</strong>sula<strong>Undaria</strong> is widespread on mussel farms around the Corom<strong>and</strong>el Pen<strong>in</strong>sula. It is well established on mussel farmstructures from Moturua Isl<strong>and</strong> (off the Papa Aroha coast) to Wilson Bay on the west coast of the Corom<strong>and</strong>el Pen<strong>in</strong>sula.Of the thirty one mussel farms surveyed, levels of <strong>Undaria</strong> <strong>in</strong>festation were def<strong>in</strong>ed as low to medium (1-100 plants per 50m transect) on seventeen of these mussel farms, high (>100 plants per 50 m transect) on eleven farms <strong>and</strong> <strong>Undaria</strong> wasnot seen on three of the farms <strong>in</strong>spected. The three mussel farms where <strong>Undaria</strong> was not recorded were at Kennedy Bay(two farms) <strong>and</strong> Port Charles (one farm). Small amounts of <strong>Undaria</strong> were found on an adjacent mussel farm at PortCharles <strong>and</strong> on a moor<strong>in</strong>g l<strong>in</strong>e at Kennedy Bay which is an <strong>in</strong>dication that <strong>Undaria</strong> is likely to be present on the musselfarms dur<strong>in</strong>g peak grow<strong>in</strong>g season or when conditions are more favourable, such as when mussel l<strong>in</strong>es have been <strong>in</strong> thewater for longer. <strong>Undaria</strong> may have been present on l<strong>in</strong>es not <strong>in</strong>spected <strong>in</strong> this survey. <strong>Undaria</strong> is known to require highlight levels for successful growth <strong>and</strong> reproduction (Stuart, 2004). Hence <strong>Undaria</strong> was generally concentrated on the upper2 m of mussel l<strong>in</strong>es with densities decl<strong>in</strong><strong>in</strong>g rapidly at greater depths, consistent with Duder (2009) <strong>and</strong> Chen (2012).<strong>Undaria</strong> <strong>in</strong>festation levels tended to be higher on mussel l<strong>in</strong>es with mussels larger than 60mm present. Mussels of a sizeof ~60 mm will have been grow<strong>in</strong>g for 5-7 months, therefore giv<strong>in</strong>g <strong>Undaria</strong> this same amount of time to colonise the l<strong>in</strong>es.The high density <strong>Undaria</strong> populations found on the three mussel farms around Motukopake Isl<strong>and</strong> <strong>and</strong> one off WhanganuiIsl<strong>and</strong> were on l<strong>in</strong>es with large mussels, 80-120mm. These farms were also <strong>in</strong>fested with the other <strong>in</strong>vasive species StyelaClava <strong>and</strong> Codium fragile ssp. tomentosoides as well as native seaweeds (e.g., Ecklonia radiata, Sargassum ssp.) <strong>and</strong>other encrust<strong>in</strong>g organisms, <strong>in</strong>dicat<strong>in</strong>g a low level of farm ma<strong>in</strong>tenance or clean<strong>in</strong>g at these sites. Clean<strong>in</strong>g of the floats<strong>and</strong> other <strong>in</strong>frastructure at small mussel farm<strong>in</strong>g sites does appear to reduce <strong>Undaria</strong> biomass on the farms. However,even well cleaned mussel farms were seen to have “hot spots” of <strong>Undaria</strong> <strong>in</strong>festation at the ends of l<strong>in</strong>es <strong>and</strong> on warp l<strong>in</strong>eswhich are not pulled out of the water <strong>and</strong> cleaned as regularly as the rest of the floats <strong>and</strong> l<strong>in</strong>es. These “hot spots” maythen act as reservoirs from which <strong>Undaria</strong> can spread back across mussel dropper l<strong>in</strong>es <strong>and</strong> floats when they aredeployed at a site.The seven mussel farms surveyed with<strong>in</strong> the WBMFZ had <strong>Undaria</strong> present at more than 500 plants per 50m transect.These farms appeared well ma<strong>in</strong>ta<strong>in</strong>ed, with no “oversized” mussels <strong>and</strong> with low levels of other pest species present. Thevigour <strong>and</strong> density of the populations seen here, by far the largest aquaculture site surveyed, may be due to the fact thatthis is the most long established population of <strong>Undaria</strong>, it is where <strong>Undaria</strong> was first noted <strong>in</strong> the Corom<strong>and</strong>el region <strong>in</strong>1999 (Jessop, 2006). The size, ~1250ha, <strong>and</strong> nature of the WBMFZ likely ensures a constant <strong>and</strong> immense supply of<strong>Undaria</strong> spores at this site. This high propagule pressure is likely to perpetuate the dense population at this site despitediffer<strong>in</strong>g stages of mussel growth <strong>and</strong> l<strong>in</strong>e/float rotation at <strong>in</strong>dividual farms with<strong>in</strong> the Zone. Further <strong>in</strong>vestigation <strong>in</strong>toenvironmental <strong>in</strong>fluences could reveal other factors promot<strong>in</strong>g the growth <strong>and</strong> proliferation of <strong>Undaria</strong> at this site.Coastal survey results <strong>in</strong>dicate that <strong>Undaria</strong> has not extensively <strong>in</strong>vaded coastal sites adjacent to Corom<strong>and</strong>el musselfarm locations. <strong>Undaria</strong> was found at six out of the twenty six coastal sites surveyed. In general, numbers found at thecoastal sites were relatively low compared to densities found on the farms, total numbers seen at <strong>in</strong>dividual coastal siteswere between one <strong>and</strong> fifty plants. At this stage it is unknown whether the low densities are a result of recent colonisation<strong>and</strong> therefore <strong>in</strong>sufficient time for establishment of large populations, whether other mechanisms may prevent theestablishment of large populations at these coastal sites, or if the tim<strong>in</strong>g of some surveys may have co<strong>in</strong>cided with lowdensities of plants. <strong>Undaria</strong> was found <strong>in</strong> shallow reef habitats with easily colonisable open spaces. It was not found to bepresent at comparable sites with dense macroalgal canopies. Plants were seen to be colonis<strong>in</strong>g areas of small to mediumboulders or patches of clear rocky reef <strong>in</strong>side the subtidal algal belt or adjacent to it at the low-<strong>in</strong>tertidal or reef-s<strong>and</strong>border.Coastal sites adjacent to mussel farms potentially present less favourable conditions for the colonisation of <strong>Undaria</strong> thanthe mussel farms themselves. The abundance of <strong>Undaria</strong> on float<strong>in</strong>g <strong>and</strong> suspended structures may be l<strong>in</strong>ked to thereduction <strong>in</strong> graz<strong>in</strong>g pressure which occurs on these surfaces as opposed to coastal sites (Castric-Fey et al, 1993; Floc’het al, 1998; S<strong>in</strong>ner et al, 2000). Relatively low densities at coastal sites could reflect poor dispersal to these locations or23
high levels of predation <strong>and</strong> competition <strong>in</strong> these areas. While relatively low densities of grazers such as sea urch<strong>in</strong>s wereobserved on the adjacent reefs, most of the reefs adjacent to farms were dom<strong>in</strong>ated by dense macroalgal st<strong>and</strong>s ofEcklonia radiata, Carpophyllum maschalocarpum <strong>and</strong>/or C. flexuosum. Therefore it is likely that dense st<strong>and</strong>s of perennialmacroalgae adjacent to farms may play a role <strong>in</strong> prevent<strong>in</strong>g or slow<strong>in</strong>g the colonisation of <strong>Undaria</strong> at these sites. Thepresence of other kelp species (e.g. Ecklonia radiata) does however <strong>in</strong>dicate favourable conditions for <strong>Undaria</strong> growtharound these sites if it were to become established (Stuart <strong>and</strong> McClary, 2004).The short life span of <strong>Undaria</strong> spores results <strong>in</strong> a “step-wise” colonisation pattern (Gurois et al, 2011) as the short livedspores only travel 100m or so from the parent plants (Forrest et al, 2001). Drift<strong>in</strong>g plants <strong>and</strong>/or fragments that releasespores can be important modes of spread for seaweeds (Forrest et al, 2001). The harvest<strong>in</strong>g of mussels <strong>and</strong> otheroperational procedures on <strong>Undaria</strong> <strong>in</strong>fested mussel l<strong>in</strong>es would strip off such material <strong>and</strong> release it <strong>in</strong>to the surround<strong>in</strong>genvironment. The distance these plants or fragments travel depends on the water currents (Forrest et al, 2001; Torres etal, 2004: Verlaque, 2007). Given that <strong>Undaria</strong> does not have bladders, drift is not likely to facilitate the long distancespread of <strong>Undaria</strong> (Parsons, 1994). This limited ability to spread naturally via spore release (S<strong>in</strong>ner et al, 2000) or float<strong>in</strong>greproductive material (Parsons, 1994) results <strong>in</strong> what Russell et al (2007) refer to as a lag phase which lasts “a few years”be<strong>in</strong>g observed before <strong>Undaria</strong> <strong>in</strong>vades areas beyond its found<strong>in</strong>g population. Range expansion is also reliant on theappropriate substrate be<strong>in</strong>g available for colonisation. <strong>Undaria</strong> prefers primarily to colonise areas clear of other alga (Hay,1990), but has been seen to penetrate the kelp <strong>and</strong> fucoid zone, compet<strong>in</strong>g with native species after be<strong>in</strong>g established forlong enough to overcome the <strong>in</strong>itial lag phase (Russell et al, 2007). It should be noted that “Natural rates of dispersal are,however, likely to depend on local conditions, <strong>and</strong> may <strong>in</strong> any case be secondary importance to human-mediateddispersal” (Stuart 2004). Vessel hulls <strong>and</strong> aquaculture equipment are thought to be the ma<strong>in</strong> dispersal pathways (Hay,1990; Neill, 2008; Russell et al, 2008; S<strong>in</strong>ner et al, 2000; Verlaque, 2007). The macroscopic sporophytes as well as themicroscopic gametophyte stage can be spread by vessels of all sizes (S<strong>in</strong>ner et al, 2000) <strong>and</strong> the easily transportablemicroscopic phase is present at much greater levels over the summer when water temperatures are the highest,co<strong>in</strong>cid<strong>in</strong>g with the period of most recreational boat traffic (Thornber et al, 2004). Mar<strong>in</strong>e farm<strong>in</strong>g equipment <strong>and</strong> spat areknown to facilitate the transfer of <strong>Undaria</strong> from place to place (Perez et al, 1991; Stuart, 1997), as well as general fish<strong>in</strong>ggear such as ropes, anchors, crayfish pots, nets <strong>and</strong> div<strong>in</strong>g gear (S<strong>in</strong>ner et al, 2000).Although the surveys carried out were extensive, proof of absence of <strong>Undaria</strong> <strong>in</strong> coastal areas adjacent to mussel farmsites is difficult to assert when <strong>distribution</strong> could be discont<strong>in</strong>uous <strong>and</strong> surveys were not all <strong>in</strong>clusive. Some of the coastalsurveys were carried out <strong>in</strong> late summer when <strong>Undaria</strong> is typically at its lowest abundance (see below). Nevertheless,based on our monitor<strong>in</strong>g data <strong>and</strong> observations at Kirita we would still have expected to see low numbers of plants oraged sporophylls at coastal sites dur<strong>in</strong>g the summer months. The benthic habitat surround<strong>in</strong>g the boat ramps surveyed atPort Charles, Te Kouma, Waikawau <strong>and</strong> at Takawhare Bay was similar to that of coastal sites where <strong>Undaria</strong> was foundadjacent to mussel farms. The absence of <strong>Undaria</strong> at these popular recreational boat<strong>in</strong>g sites <strong>and</strong> the sw<strong>in</strong>g moor<strong>in</strong>gs atTakawhare Bay <strong>in</strong>dicates that the spread of <strong>Undaria</strong> around the Corom<strong>and</strong>el may not be closely associated withrecreational nautical activities.No <strong>Undaria</strong> plants were sighted on the mussel barge hulls at W<strong>in</strong>dy Po<strong>in</strong>t/Puhi Rare, but presence <strong>and</strong> transport of the<strong>Undaria</strong> gametophytes via barge hulls is highly likely. The absence of <strong>Undaria</strong> plants at the mussel barge moor<strong>in</strong>g sitecould possibly be due to the unsuitable nature of the habitat found there. This site is an <strong>in</strong>ner Harbour site with highturbidity, Secchi depth 2.7m. Another reason for the absence of <strong>Undaria</strong> may be the frequent use of the barges notallow<strong>in</strong>g for the growth of visible <strong>Undaria</strong> plants.Mussel farm sites are <strong>in</strong>herently areas with good water flow <strong>and</strong> sufficient nutrients to provide for the rapid growth <strong>and</strong>health of mussels for commercial harvest<strong>in</strong>g. The provision of artificial substrates such as l<strong>in</strong>es <strong>and</strong> floats <strong>in</strong> the highlyillum<strong>in</strong>ated shallow water (
perennial macroalgae. Instead, plants were seen to be colonis<strong>in</strong>g areas of small to medium boulders or patches of rockyreef where canopy-form<strong>in</strong>g algae were lack<strong>in</strong>g such as adjacent to the reef-s<strong>and</strong> <strong>in</strong>terface or <strong>in</strong> low-<strong>in</strong>tertidal areasdom<strong>in</strong>ated by corall<strong>in</strong>e turf (Corall<strong>in</strong>a offic<strong>in</strong>alis). In general all plants recorded at coastal sites were very shallow (
zone are 50-100plants mˉ² or less (Brown <strong>and</strong> Lamare, 1994; Brown, 1999; S<strong>in</strong>ner et al, 2000). This is consistent withdata from other populations outside its native range (Castric-Fey et al, 1993; Campbell <strong>and</strong> Burridge, 1998).Seawater nutrient data showed a higher availability of nitrogen dur<strong>in</strong>g the w<strong>in</strong>ter months. Nitrogen levels <strong>in</strong> sea water areknown to be lowest <strong>in</strong> the summer <strong>and</strong> highest <strong>in</strong> w<strong>in</strong>ter with<strong>in</strong> temperate coastal waters <strong>and</strong> ammonia <strong>and</strong> phosphate arepresent at consistent concentrations throughout the year (Dean <strong>and</strong> Hurd, 2007) as was observed, although ammonialevels were highly variable over the summer months (from November onwards).The availability of seawater nutrients is one of the primary factors regulat<strong>in</strong>g the growth, reproduction <strong>and</strong> biochemistry ofseaweeds, with evidence suggest<strong>in</strong>g that N, P <strong>and</strong> Fe can limit the growth of seaweeds (Lobban <strong>and</strong> Wynne, 1981).<strong>Undaria</strong> crop yield <strong>in</strong> Asia is commonly <strong>in</strong>creased through the application of nitrogen fertilisers (Dean, 1998). Seawaternutrient levels from temporal monitor<strong>in</strong>g sites showed overall seawater nutrient concentrations were similar between theCorom<strong>and</strong>el <strong>and</strong> Westhaven Mar<strong>in</strong>a monitor<strong>in</strong>g sites, this <strong>in</strong>dicates the mussel farm does not <strong>in</strong>fluence these seawaternutrient levels at the Corom<strong>and</strong>el site. These results agree with those of an <strong>in</strong>vestigation by Duder (2009) which found thatmussel aquaculture around Great Barrier Isl<strong>and</strong> did not raise seawater nutrient levels or enhance the growth of <strong>Undaria</strong>.5.3. Other <strong>in</strong>vasive speciesStyela clava was found on all the mussel farms surveyed <strong>and</strong> Codium fragile ssp. tomentosoides was present on twentyeight out of the thirty one farms surveyed. Both these species are known for be<strong>in</strong>g <strong>in</strong>troduced <strong>and</strong> spread via shellfishaquaculture (Pagad, 2012). They also have the potential to impact negatively upon both the mussel farm<strong>in</strong>g <strong>in</strong>dustrythrough heavy foul<strong>in</strong>g <strong>and</strong> on native benthic communities by outcompet<strong>in</strong>g native species for resources. Charybdisjaponica, the Asian paddle crab, was found at two coastal sites. This species could impact negatively upon native benthiccommunities though competition for space <strong>and</strong> resources with native crab species. Charybdis japonica is also known totransmit disease <strong>and</strong> prey on native shellfish, which is a potential threat to local fisheries <strong>and</strong> shellfish (Pagad, 2012).5.4. Implications <strong>and</strong> considerationsAll the mussel farm sites surveyed had similar environmental conditions <strong>and</strong> all provide suitable habitat for the colonisation<strong>and</strong> growth of <strong>Undaria</strong>. The open structures supply shallow, well illum<strong>in</strong>ated substrate free from graz<strong>in</strong>g pressures <strong>and</strong>competitive algal species. The farms are positioned <strong>in</strong> areas of good water flow <strong>and</strong> with sufficient nutrients to provide forthe rapid growth <strong>and</strong> health of mussels for commercial harvest<strong>in</strong>g, sal<strong>in</strong>ity read<strong>in</strong>gs taken dur<strong>in</strong>g the spatial <strong>and</strong> thetemporal surveys showed little freshwater <strong>in</strong>fluence over time or between sites. These conditions are consistent with ideal<strong>Undaria</strong> habitat (Verlaque, 2007). In general the longer the mussel ropes have been <strong>in</strong> the water grow<strong>in</strong>g the mussels thegreater potential there is for <strong>Undaria</strong> to grow on the l<strong>in</strong>es. The dense populations of large <strong>Undaria</strong> plants seen at theWBMFZ <strong>and</strong> on the four other heavily <strong>in</strong>fested farms on the western Corom<strong>and</strong>el will have strong impacts on lightavailability, nutrient cycl<strong>in</strong>g <strong>and</strong> food availability for the mussels be<strong>in</strong>g grown on these farms (Cecere et al., 2000; Henkel<strong>and</strong> Hofmann, 2008).The dense population seen at the WBMFZ, where heavy <strong>in</strong>festations <strong>in</strong>cluded the presence of all life stages of <strong>Undaria</strong>plants on both site visits, ensures a constant <strong>and</strong> immense supply of spores at this site. This high propagule pressure islikely to perpetuate the extensive population at this site despite differ<strong>in</strong>g stages of mussel growth <strong>and</strong> l<strong>in</strong>e/float rotation at<strong>in</strong>dividual farms with<strong>in</strong> the MFZ. For smaller mussel farms, clean<strong>in</strong>g of the floats <strong>and</strong> other <strong>in</strong>frastructure does appear toreduce the prevalence <strong>and</strong> potential effects of <strong>Undaria</strong>, as well as other <strong>in</strong>vasive species at these sites.<strong>Undaria</strong> was found at six coastal sites. Plants were found with<strong>in</strong> one of the 50m transects at each of these sites. Sampl<strong>in</strong>gwas concentrated on the shallow-subtidal marg<strong>in</strong> of the reef, typically just below the low-tide mark. Much of the reefadjacent to the farms <strong>in</strong> the western Corom<strong>and</strong>el is of a similar physical composition, relatively shallow, with a s<strong>and</strong>-reefborder at depths of less than 5 m <strong>and</strong> a limited offshore extent of 15-30 m. Although many of the sites surveyed weresimilar <strong>in</strong> nature it was not possible to easily predict the presence or absence of <strong>Undaria</strong>. The factors <strong>in</strong>volved <strong>in</strong> theestablishment of <strong>Undaria</strong> populations at coastal sites are likely to be complex <strong>and</strong> site specific (S<strong>in</strong>ner et al, 2000).Graz<strong>in</strong>g by urch<strong>in</strong>s, fish <strong>and</strong> molluscs, <strong>and</strong> <strong>in</strong>teractions with other macroalgae are potential <strong>in</strong>fluences which are difficult toquantify but have been shown to be important <strong>in</strong> determ<strong>in</strong><strong>in</strong>g the colonisation success <strong>and</strong> impact of <strong>Undaria</strong> (Valent<strong>in</strong>e26
<strong>and</strong> Johnson, 2003). Through this survey it was apparent that <strong>Undaria</strong> will colonise open spaces as opposed to <strong>in</strong>vad<strong>in</strong>g<strong>in</strong>tact algal communities. Therefore, it seems that ensur<strong>in</strong>g the ma<strong>in</strong>tenance of healthy native macroalgal canopies willhelp <strong>in</strong> prevent<strong>in</strong>g the spread of <strong>Undaria</strong> to coastal reef habitats. As <strong>Undaria</strong> is be<strong>in</strong>g found <strong>in</strong> more northern regions ofNew Zeal<strong>and</strong> it is worth not<strong>in</strong>g that urch<strong>in</strong> barrens, where large brown macroalgae are rare, are common on waveexposedreefs <strong>in</strong> north-eastern New Zeal<strong>and</strong> (Shears <strong>and</strong> Babcock 2004). Such habitats are highly vulnerable to theestablishment of <strong>and</strong> facilitat<strong>in</strong>g the spread of <strong>Undaria</strong> (Valent<strong>in</strong>e <strong>and</strong> Johnson, 2003). Currently mussel farm<strong>in</strong>g activitiesare primarily restricted to the more sheltered locations <strong>in</strong> the Hauraki Gulf where urch<strong>in</strong> barrens habitats typically don’toccur. Any plans to exp<strong>and</strong> mussel farm<strong>in</strong>g or aquaculture activities to more exposed parts of the Hauraki Gulf should takethis <strong>in</strong>to account. <strong>Undaria</strong> may still be experienc<strong>in</strong>g a “lag phase” around the Corom<strong>and</strong>el Pen<strong>in</strong>sula which would implicatemuch more rapid establishment is likely to occur at coastal sites as found<strong>in</strong>g populations, at mussel farm sites, cont<strong>in</strong>ue toproliferate. We recommend that further monitor<strong>in</strong>g <strong>and</strong> research be carried out around the Corom<strong>and</strong>el region to moreaccurately ascerta<strong>in</strong> the extent of <strong>Undaria</strong> <strong>in</strong>festation around the Corom<strong>and</strong>el coast <strong>and</strong> determ<strong>in</strong>e the factors <strong>in</strong>fluenc<strong>in</strong>gthe abundance of <strong>Undaria</strong> at mar<strong>in</strong>e farm<strong>in</strong>g <strong>and</strong> coastal sites. Annual monitor<strong>in</strong>g of <strong>Undaria</strong> populations could helpunderst<strong>and</strong> the spread of populations, the possibility that <strong>Undaria</strong> is currently <strong>in</strong> a “lag phase” of coastal <strong>in</strong>vasion, <strong>and</strong> thepotential risks to coastal environments <strong>and</strong> native species.The <strong>in</strong>fluences of aquaculture activity on the success of <strong>Undaria</strong> are still largely unknown. Although <strong>Undaria</strong> has notspread extensively to coastal areas adjacent to mussel farms on the Corom<strong>and</strong>el Pen<strong>in</strong>sula it is apparent that <strong>in</strong>troduc<strong>in</strong>gmussel farm <strong>in</strong>frastructure to a site will likely result <strong>in</strong> the <strong>in</strong>troduction of <strong>Undaria</strong> to that site. If mussel farms are to beplaced <strong>in</strong> High Value Conservation areas or areas near mar<strong>in</strong>e reserves it must be taken <strong>in</strong>to consideration that <strong>Undaria</strong>will then be <strong>in</strong>troduced to these areas. Careful <strong>and</strong> regular ma<strong>in</strong>tenance of exist<strong>in</strong>g mussel farms <strong>and</strong> associatedequipment will help towards m<strong>in</strong>imis<strong>in</strong>g the spread of <strong>Undaria</strong> to coastal areas as well as new mar<strong>in</strong>e farms. Un-<strong>in</strong>festedcoastal reef sites at risk of <strong>Undaria</strong> colonisation may be those with impaired or reduced native algal canopies or abundantnatural open spaces <strong>in</strong> the shallow subtidal zone.27
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Appendix 1 - Maps of <strong>Undaria</strong> <strong>in</strong>festation at mussel farms, “high risk” <strong>and</strong> coastalsurvey sitesGreen paths <strong>in</strong>dicate no <strong>Undaria</strong> was sighted, orange paths represent sites where <strong>Undaria</strong> plants were seen atnumbers 1-100 per 50m transect (averaged across the transects surveyed) <strong>and</strong> red l<strong>in</strong>es <strong>in</strong>dicate <strong>Undaria</strong> waspresent at >100 plants per 50m transect when averaged across the transects.21Kennedy Bay34Port Charles30
5Moturua Isl<strong>and</strong>6101112897Koputauaki Bay, Motukakarikitahi <strong>and</strong> Motukopake Isl<strong>and</strong>s131418171615Whanganui Isl<strong>and</strong> <strong>and</strong> Corom<strong>and</strong>el Harbour31
1920232221Manaia Harbour24Kirita Bay, Wekarua Isl<strong>and</strong>, Manaia Harbour2526272829303132Wilson Bay
33Takawhare Bay, W<strong>in</strong>dy Po<strong>in</strong>t/Puhe Rare, Hannaford’s jetty <strong>and</strong> Te Kouma boat ramp
Appendix 2 –Summary of coastal transect <strong>in</strong>formationDateLocation22/11/2011 Port Charles23/11/2011 Moturua Isl<strong>and</strong>23/11/2011 Koputauaki Bay23/11/201123/11/2011MotukapakeIsl<strong>and</strong> (east)MotukakarikitahiIsl<strong>and</strong>23/11/2011 Whanganui Isl<strong>and</strong>6/12/20116/12/2011Wilson Bay(Kereta)Wilson bay(Kereta North)7/12/2011 Kirita Bay7/12/20117/12/20111/02/20121/02/20121/02/2012Corom<strong>and</strong>elHarbour west(Papakarahi Bay)Manaia (WekaruaIsl<strong>and</strong>)Kennedy BaynorthKennedy Baysouth westKennedy Baysouth east1/02/2012 Port Charles22/02/2012 Motukopake east2/02/2012 Motukopake west2/02/2012 Manaia north2/02/20122/02/20123/02/2012Manaia -Ohauhunga BayManaia - OnepotoBayCorom<strong>and</strong>elHarbour west3/02/2012 Kirita BayGPSCo-ord<strong>in</strong>ates36º 30’ 51 S175º 28’ 13 E36 º 41’ 57 S175º 23’ 48 E36 º 43’ 47 S175º 26’ 42 E36 º 45’ 22 S175º 25’ 21 E36 º 45’ 26 S175 º 27’ 07 E36º 47’ 35 S175 º 26’ 14 EWest: 36º 53’ 09 S175º 25’ 24 EEast: 36º 53’ 13 S175º 25’ 32 E36º 53’ 24 S175º 25’ 35 ENorth: 36º 51’ 49 S175º 24’ 41 ESouth: 36º 51’ 59 S175º 24’ 47 E36º 48‘ 27 S175º 27’ 11 E36º 50’ 30 S175º 25’ 17 E36º 40’ 08 S175º 34’ 21 E36º 41’ 12 S175º 34’ 04 E36º 40’ 45 S175º 34’ 45 E36º 31’ 07 S175º 28’ 15 E36º 45’ 22 S175º 25’ 21 E36º 45’ 16 S175º 25’ 11 E36º 50’ 08 S175º 25’ 46 E36º 50’ 59 S175º 25’ 21 EEast: 36º 50’ 59 S175º 24’ 38 EMid: 36º 51’ 12 S175º 24’ 37 EWest: 36º 51’ 12 S175º 24’ 28 EEast: 36º 48’ 38 S175º 26’ 13 EWest: 36º 48’ 53 S175º 25’ 59 E36º 51’ 49 S175º 24’ 41 ENumber ofTransectsTotal DistanceCovered (m)<strong>Undaria</strong>Category16 800 010 500 0 Styela Clava13 650 0 Styela Clava7 350 08 400 09 450 0 Styela Clava5 250 0 Styela Clava8 400 1 Styela Clava9 450 212 600 18 400 116 800 05 250 05 250 03 150 013 650 019 950 112 600 012 600 0 Styela Clava15 750 015 750 01 50 2Other Invasive SpeciesSightedStyela Clava, Codium fragilessp. tomentosoidesCodium fragile ssp.tomentosoides, Styela ClavaCodium fragile ssp.tomentosoides, Styela ClavaCodium fragile ssp.tomentosoides, StyelaClava, Charybdis japonica34
3/02/2012 Kereta South 36º 54’ 14 S175º 25’ 53 E3/02/2012 Waikawau 36º 56’ 12 S175º 27’ 59 E11 550 012 600 0Codium fragile ssp.tomentosoides, StyelaClava, Charybdis japonicaTotal 244 12100*GPS co-ord<strong>in</strong>ates are given for the approximate centre of the set of coastal transects surveyed or the approximate areawhere <strong>Undaria</strong> was sighted if the location was positive for <strong>Undaria</strong>.35
Appendix 3 – Summary of mussel farm survey <strong>in</strong>formationAppendix 3A: Mussel farm <strong>in</strong>vasive species <strong>in</strong>formationDateLocation1/02/2012 Kennedy Bay22/11/2011 Port Charles1/02/2012 Port Charles23/11/2011 MoturuaIsl<strong>and</strong>23/11/2011 KoputauakiBay23/11/2011 Motukakarikitahi Isl<strong>and</strong>2/02/2012MotukopakeIsl<strong>and</strong>23/11/2011 MotukopakeIsl<strong>and</strong>2/02/2012MotukopakeIsl<strong>and</strong>23/11/2011 WhanganuiIsl<strong>and</strong>7/12/20113/02/2012Corom<strong>and</strong>elHarbourCorom<strong>and</strong>elHarbour2/2/2012 Manaia North7/12/2011Manaia(WekaruaIsl<strong>and</strong>)GPSCo-ord<strong>in</strong>ates*36º 40’ 22 S175º 34’ 12 E36º 40’ 21 S175º 34’ 12 E36º 30’ 47 S175º 28’ 00 E36º 30’ 47 S175º 28’ 00 E36º 30’ 54 S175º 28’ 03 E36º 41’ 56 S175º 23’ 56 E36º 44’ 02 S175º 26’ 56 E36º 45’ 20 S175º 27’ 11 E36º 45’ 11 S175º 25’ 25 E36º 45’ 19 S175º 25’ 35 E36º 45’ 19 S175º 25’ 35 E36º 45’ 09 S175º 20’ 02 E36º 45’ 15 S175º 25’ 01 E36º 45’ 21 S175º 24’ 58 E36º 47’ 40 S175º 26’ 20 E36º 48’ 22 S175º 27’ 10 E36º 48’ 28 S175º 26’ 17 E36º 48’ 33 S175º 26’ 10 E36º 48’ 40 S175º 26’ 06 E36º 48’ 44 S175º 25’ 55 E36º 50’ 06 S175º 25’ 39 E36º 50’ 32 S175º 25’ 23 EFarmNumberL<strong>in</strong>esNumber ofTransects<strong>Undaria</strong>Category1 2,9,12,21 10 02 7,8,12,21 10 03 1,6,9 6 131,2,4,6,13,1514 04 3,5,9,10 8 0PopulationStructureDegradedsporophytes5 1,4,8,12 8 1 Sporophytes6 2,4,8 6 2 Sporophytes71,3,4,5,7,9,1414 2Plantlets <strong>and</strong>sporophytes8 1,2,3,6,10 12 2 All life stages Styela Clava9 2,5,6,7,10 12 2 Sporophytes9 1,3,4 6 3 All life stages10 1,2,4,7,9 10 3 All life stages11 1,3,4,7,9 10 1Degradedsporophylls12 1,3,6,7,10 12 3 All life stages13 2,6,10 6 3 All life stages14 1,3 4 2 Sporophytes15 1,3,4 6 1 All life stagesOther Invasive SpeciesSightedCodium fragile ssp.tomentosoidesCodium fragile ssp.tomentosoidesCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoidesCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoidesCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoidesCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides16 2,9,14 6 1 Plantlets Styela Clava17 2,4 4 2 All life stages Styela Clava18 10,15 4 1Degradedsporophytes <strong>and</strong>sporophyllsCodium fragile ssp.tomentosoides19 2,7,1,1 8 1 All life stages Styela Clava20 1,2,3,6 8 2 SporophytesCodium fragile ssp.tomentosoides, StyelaClava36
2/02/2012 Manaia7/12/20116/12/20116/12/20116/12/20113/02/20123/02/20126/12/20116/12/2011Kirita(MatarikiIsl<strong>and</strong>)Wilson BayMFZWilson BayMFZWilson BayMFZWilson bayMFZWilson BayMFZWilson BayMFZWilson BayMFZ36º 50’ 49 S175º 25’ 13 E36º 50’ 55 S175º 24’ 40 E36º50’ 56 S175º 24’ 30 E36º 50’ 56 S175º 24’ 30 E36º 51’ 55 S175º 24’ 35 E36º 53’ 55 S175º 24’ 12 E36º 54’ 36 S175º 23’ 08 E36º 55’ 35 S175º 25’ 22 E36º 55’ 37 S175º 25’ 56 E36º 55’ 52 S175º 26’ 12 E36º 56’ 16 S175º 26’ 34 E36º 56’ 45 S175º 25’ 45 E21 1,4,13,16 10 2 All life stages22 1,2,6,7 8 1 All life stages23 1,5,9,13 8 2 All life stages23 1,5,9 6 2 All life stagesCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.Tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClava24 1,2,3,5 8 1 Small sporophytes Styela Clava25 1,3,6 6 4 All life stages26 1,3,4,6 8 4 All life stages27 2,3,5 6 4 All life stages28 1,2,3,10,13 10 4 All life stages29 1,4,9,12 10Total 31 132 2684All life stages30 1,3,6 6 4 All life stages31 1,3,6 6 4 All life stagesCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClavaCodium fragile ssp.tomentosoides, StyelaClava*GPS co-ord<strong>in</strong>ates are given for the approximate centre of each mussel farm surveyed.37
Appendix 3B: Mussel farm site environmental <strong>in</strong>formationDate Location Farm Number Time Sal<strong>in</strong>ity Depth (m) Secchi depth (m) Temperature (˚C) Weather conditions22/11/2011 Port Charles 3 11:00 35.4 12.0 6.5 16.0 Sunny23/11/2011 Moturua Isl<strong>and</strong> 5 15:00 35.1 10.0 8 17.0 Overcast23/11/2011 Koputauaki Bay 6 9:00 35.1 10.0 4 17.0 Overcast23/11/2011 Motukopake Isl<strong>and</strong> (East) 8 11:15 35.5 22.0 7.5 17.0 Sunny23/11/2011 Motukakarikitahi Isl<strong>and</strong> 7 15:00 33.5 19.0 6.5 17.0 Overcast24/11/2011 Whanganui Isl<strong>and</strong> 13 17:00 35.3 7.8 5 17.0 Cloudy6/12/2011 Wilson Bay MFZ farm #27 25 9:30 34.2 24.2 8.5 18.1 Overcast/showers6/12/2011 Wilson Bay MFZ farm #39 26 11:00 34.2 23.0 6.5 18.1 Overcast/showers6/12/2011 Wilson Bay MFZ farm #89 27 13:00 34.4 19.0 4.5 18.2 Sunny/cloudy6/12/2011 Wilson Bay MFZ farm #142 31 15:15 34.4 16.0 4.5 18.2 Overcast6/12/2011 Wilson Bay MFZ farm #173 30 16:05 34.1 15.0 6.5 18.2 Overcast7/12/2011 Kirita Bay 24 8:45 34.4 6.0 6 (bottom) 18.2 Overcast7/12/2011 Wekarua Isl<strong>and</strong> 20 10:30 34.7 13.0 8 18.1 Overcast/showers1/02/2012 Kennedy Bay 1&2 12:30 34.5 8.0 7 19.3 Half cloud/overcast1/02/2012 Port Charles 4 17:30 35.5 9.2 6 19.1 Cloudy/overcast2/02/2012 Motukopake Isl<strong>and</strong> (East) 8 9:30 35.0 10.3 6.5 19.4 Overcast2/02/2012 Motukopake Isl<strong>and</strong> (West) 11 11:15 34.7 9.0 6 19.4 Overcast2/02/2012 Corom<strong>and</strong>el Harbour 16 1:30 35.0 10.4 5 19.8 Overcast2/02/2012 Manaia LI357 19 15:00 34.5 8.5 5.5 20.6 Sunny/partly cloudy2/02/2012 Manaia LI376 21 14:00 35.0 8.3 4.5 20.1 Overcast2/02/2012 Manaia LI308 23 18:00 35.0 8.3 4.5 20.1 Overcast3/02/2012 Kirita bay 24 9:00 34.5 6.0 5.5 19.2 Overcast3/02/2012 Wilson Bay MFZ 28 & 29 9:30 34.5 16.8 4.5 20.0 Overcast38
Appendix 4 - Size frequency <strong>distribution</strong> of monitored <strong>Undaria</strong> populationsWesthaven Mar<strong>in</strong>a.160 r<strong>and</strong>om plants were measured every month.1001008060July8060January40402020080604020August010080604020February008060September8060March40402020008060October8060April4040202000806040200806040200NovemberDecember1008060May40200100Total length (mm)39
Corom<strong>and</strong>el HarbourThe plants present on the 40 sampl<strong>in</strong>g floats were measured every month.Note: no sampl<strong>in</strong>g was carried out <strong>in</strong> September 201130252015105025201510502520151050252015105025201510502520151050JuneJulyAugustOctoberNovemberDecember30252015105025201510502520151050252015105025201510502520JanuaryFebruaryMarchAprilMayJune151050100100Total length (mm)40