Spatial distribution and seasonal variation in Undaria pinnatifida ...

3.1.2. Coastal reef locationsContiguous 50 x 10m transects were run along sections of coast adjacent to all mussel farm locations on the CoromandelPeninsula. A total of twenty six coastal reef areas were surveyed via SCUBA and/or snorkel. In New Zealand, Undariapopulations that occur on native reef habitats are typically densest from the low intertidal fringe down to approximatelythree metres (Brown and Lamare, 1994; Parsons, 1994; Sinner et al, 2000; Stuart, 2004; Russell et al, 2007). Much of thereef adjacent to the farms in the western Coromandel is relatively shallow, with a sand-reef border at depths of less than5m and a limited offshore extent of 15-30m. Sampling was concentrated on the shallow-subtidal margin of the reef,typically just below the low-tide mark. The depth of the surveys conducted ranged from one to five metres, depending onhabitat and 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 coastline, five coastal sites were selected where subtidal reef habitatoccurred that could potentially be colonised by Undaria. A total of 2250 meters of this adjacent coast was surveyed. Thenature of the benthic environment and algal species present was recorded for each 50m transect. The presence of otherinvasive species was noted.Surveys were carried out between November 22 nd 2011 and February 3 rd 2012. To examine the potential for differences intiming of surveys to influence the presence or infestation level of Undaria two sites where Undaria was recorded inNovember were revisited in February and Undaria populations were qualitatively compared.3.1.3. Other “high risk” locationsIn order to investigate the potential spread of Undaria by recreational vessels, seven “high risk” sites of interest weresurveyed in February 2012. These were comprised of two swing mooring sites in the Coromandel Harbour at Takawharebay and Windy Point/Puhi Rare, three boat ramps; Waikawau (Thames coast), Port Charles and the Sugarloafrecreational and mussel loading ramp at Te Kouma, a set of mooring buoys in Kennedy bay and the infrastructure atHannaford’s Jetty in the Coromandel Harbour were also surveyed. Boat ramp sites were surveyed via snorkel and/orSCUBA, surveyors searched artificial structures and surrounding coastal reef sites. The swing mooring site at WindyPoint/Puhe Rare was surveyed via SCUBA, divers inspected a random subset of moorings and mussel barge hulls. Therecreational swing moorings at Takawhare Bay were surveyed from kayaks, a random subset of mooring floats/lines andvessel hulls were inspected from the surface or mooring floats were lifted out of the water and inspected aboard thekayaks. The mooring buoys at Kennedy bay were inspected in a similar manner, by lifting them aboard a dinghy. AtTakawhare Bay 43 out of 120 listed moorings were surveyed. At Puhi Rare 12 out of the seventy listed moorings wereinspected, very poor visibility prevented more inspections at this site.3.1.4. Semi-quantitative measurements of Undaria abundanceFor each 50m section of mussel line or coast surveyed the number of Undaria plants sighted was placed in one of fivecategories, these are shown in Table 1:Table 1: Undaria infestation 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 infested (red)6