Application 124771 - Ministry of Fisheries

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MAY 2012 REPORT NO. 2134 | CAWTHRON INSTITUTE The differences in infauna communities between the reference farm and control sites were indicative of a mildly enriched benthic environment beneath farms resulting in greater abundances of opportunistic species. However, in most cases the subtle differences observed were in the abundance of species, rather than their presence or absence, suggesting that infauna communities in the wider environment are already exposed to mild enrichment. This conclusion was supported when the biological and physico-chemical data were used to calculate enrichment stage (ES), and no significant difference between the ES of control and farmed sites was found. Epibiota communities at the reference farm sites were characterised by mussels and large numbers of sea stars, sea cucumbers and ascidians, and were relatively diverse compared to the sparse epifauna observed at most control sites (see Section 5.3). Scallops and horse mussels were observed inshore of some reference farm and control sites, particularly on sand- and shell-dominated substrata. A snap-shot of water column properties at the reference farm and control sites using replicate CTD casts showed a well-mixed water column at some reference farms and control sites, but a thermo- and halo- cline (stratification of temperature or salinity) was observed between 5-10 m at several reference farm sites and control sites (Section 5.4). The greatest inter-site range in salinity and temperatures was observed in the top 5-10 m of the water column. Chlorophyll-a (chl-a) was similar between reference farms and control sites throughout much of the water column. Water column turbidity was similar between the reference farms and control sites in the top 1-2 m of the water column; but there was less turbidity between 3-5 m at farm sites. At depths of 5-7 m, farm sites were more turbid, but at depths greater than 7 m, turbidity was generally lower at farm sites. All of the 32 mussel farm sites and their proposed extension areas (Appendices 7-39) appear to have been placed away from significant inshore reef and other sensitive habitats and were mainly over muddy substrata. Consequently, effects to the benthic environment were restricted to changes in infauna and epifauna abundances, related mussel drop-off and mild enrichment from the farms. Conclusions: iv 1. Our assessment of the environment beneath the reference farms in the north and south of Coromandel Harbour (from Wilsons Bay to Colville Bay) found differences in the physical and biological characteristics of benthos, when compared to control sites. Effects included minor enrichment and increased diversity of epibiota, and were equivalent to those observed beneath mussel farms elsewhere in New Zealand. 2. Farm-related effects of mild enrichment, and increased abundances of infauna and epibiota were attributable to mussel drop-off and other farm-related deposition that are not necessarily negative and would be reversible over time. The
CAWTHRON INSTITUTE | REPORT NO. 2134 MAY 2012 depositional effects did not extend to any reef or significant inshore rocky habitat at any of the 32 mussel farm sites. 3. The top 10 m of the water column had the greatest variability in salinity and temperature across both reference farms and control sites, but no consistent patterns or differences were observed in chl-a. Reference farm sites were generally found to be less turbid than control sites below a depth of 7 m, which could be attributed to filtration of the water column by mussels. Wider-scale and longer-term monitoring and validated models will be necessary to provide a greater understanding of the contribution of aquaculture to water column properties in the Coromandel region. 4. In general, the effects of mussel farms on the benthic marine environment, in terms of enrichment and modification, have been found to be minor (Keeley et al. 2011), particularly when placed over primarily muddy substrata. Here we found that the effects to the benthic environment from Coromandel inshore mussel farms are similar, if not less, than in other areas of New Zealand. Therefore, providing the proposed additional 1 ha extensions (over and above the existing consented farm areas) are placed over similar substrata, the effects to the environment are likely to be similar to those observed in this assessment. v
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Contents 2 Contents ...............
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4 marine farm (which expires on 1 J
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6 2011) identified that the aquacul
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8 Goodwin E, 2012. Assessment of Be
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10 4.5.8 The capacity of the wharf
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12 in Appendix 1 and designed in ac
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7. Relevant Planning Provisions 14
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16 the applicant is a member of the
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7.18 Policy 6.1.3 - (Integrated Man
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Appendix 1: Survey plan showing loc
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REPORT NO. 2167 COROMANDEL MUSSEL F
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Application 124771 - Ministry of Fisheries

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