Science Advisory Report  2014/017

Potential impacts of finfish aquaculture on hard bottom substrates and development of a standardized monitoring protocol

Summary

  • Visual imaging can be used as an appropriate primary tool for assessing benthic changes on predominately hard bottom substrates in aquaculture areas of Newfoundland.
  • Parameters for achieving good quality videos suitable for analysis were discussed. Factors included: resolution, added lighting and camera orientation. These methods can evolve with new technologies (camera systems, image processing software).
  • Using standardized area measurement, such as a quadrant, with the visual imaging equipment is essential in achieving consistency in the spatial coverage of video surveys.
  • Training observers to assess the videos as well as the use of the visual benthic identification guide are important elements in ensuring consistency and quality assessments.
  • Beggiatoa and OPC appear to be acceptable indicators of organic deposition.
  • Beggiatoa and OPC were not observed in reference sites and were found linked with aquaculture activities on a range of substrates.
  • Beggiatoa and OPC were found to decrease with distance from cage.
  • More sites need to be considered in order to validate DEPOMOD use to predict deposition from aquaculture farms in NL conditions.
  • The characterization of benthic assemblages across the study area shows a patchy distribution (including patchy substrates). Relationships with depth, substrate type, and proximity to finfish cages were studied. Some benthic communities were very poor with little fauna/flora presence. Benthic hypoxic conditions may exist in some sites prior to aquaculture site set-up.
  • Proper characterization of the spatial extent of areas of deposition necessitates the extension of sampling transects from cage edge beyond the current limit (50 m) to 120 m.
  • Beggiatoa and OPC were still present on fallowed sites. After a one-year fallow period, results suggest a reduction of the spatial extent of benthic organic indicators (Beggiatoa, OPC) to the area below the cages. More research is needed to draw conclusions on the fallow period efficiency in contributing towards assimilation of deposits and a return to baseline conditions.
  • The Fisheries Act amendments passed in 2012 create a fisheries protection program that will focus on the protection of fisheries and fish and fish habitat that support those fisheries. In the light of these changes, the findings of this work and its continuation will help inform the development of management thresholds.

This Science Advisory Report is from the Regional Peer Review meeting that was held May 22‑23, 2013 in St John’s, NL: Potential impacts of finfish aquaculture on hard bottom substrates and development of a standardized monitoring protocol. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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