Application 124771 - Ministry of Fisheries

CAWTHRON INSTITUTE | REPORT NO. 2134 MAY 2012
placed over similar substrata, the effects to the environment are likely to be similar to
those observed in this assessment.
All of the 32 mussel farm sites assessed in this study (Appendices 7-39) had 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 to mussel drop-off
and mild enrichment from farm biodeposits.
Conclusions:
1. Our assessment of the environment beneath reference farm sites in the
Coromandel 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 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 farm 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.
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