Science Advisory Report 2021/038

Effects of finfish aquaculture activities on hard seabed ecosystems in British Columbia and advice on monitoring protocols

Summary

• Video survey data collected between 2008 and 2011 by the finfish aquaculture industry in British Columbia (BC) and by Fisheries and Oceans Canada’s Pacific Region Aquaculture Management, as part of their audit program, were analyzed in order to address questions related to changes in benthic epifaunal distributions, to assess differences associated with finfish aquaculture organic loading, and to provide advice on potential additional indicator species and sampling design for the purposes of site monitoring. Video data were collected around peak production at finfish aquaculture sites in Jervis Inlet, Sechelt Inlet, Queen Charlotte Strait, Johnstone Strait and Western Vancouver Island. These sites represent a variety of fine sediment, mixed sediment and hard-bottom seabeds. Baseline (pre-farm) surveys were not used in this analysis and therefore pre- and post-farm epifaunal differences were not assessed.
• Beggiatoa-like bacteria were observed on 36 of the 44 farm transects (82%) and Opportunistic Polychaete Complexes (OPCs) were observed on 17 of 44 farm transects (39%). None of the reference transects assessed had visible Beggiatoa-like bacteria or OPCs.
• In some instances, an inverse relationship was observed between Beggiatoa-like bacteria and OPCs within the near-field zone of the netpen systems, where the percent coverage trend for Beggiatoa-like bacteria had an offset-peak and showed low percent coverage while OPC had high percent coverage. The relationship between OPCs and Beggiatoa-like bacteria are likely complex. When Beggiatoa-like bacteria were visible in farm transects, the trends in terms of percent coverage along the length of the video transect (i.e., distance away from a farm) were variable (constant, offset-peak, or declining trend with distance from farm).
• Overall, Beggiatoa-like bacteria are responsive to changes in benthic oxic state associated with organic loading. However, it appears that Beggiatoa-like bacteria may exhibit a peak in abundance based on the optimal oxic-anoxic gradient and sulfide concentrations, and therefore in high organic loading areas should be used in combination with other sensitive visual indicators (e.g., OPCs) for hard bottom monitoring.
• Beggiatoa-like organisms and OPCs are currently accepted indicators of organic enrichment although their respective relationships to changes in epifauna are not established.
• There are currently no additional indicators or measures of benthic community changes associated with hard bottom finfish aquaculture sites in BC that can be used as part of a weight-of-evidence approach.
• Observations of epifauna from video surveys were qualitatively compared to reference transects for farms without accounting for substrate type. Broadly speaking there were differences in the epifauna seen between the farm transects and the reference transects, but, whether these are due to organic loading associated with farm activities or differences in substrate type or oceanographic conditions, cannot be assessed at this point. Finer scale, substrate-matched analyses would be required in order to assess for differences in epifauna taxa distribution or abundance between reference transects and farm transects. The use of baseline (pre-farm) survey data would allow for analysis of benthic community change over time and production cycles.
• The potential for additional species-specific, biodiversity, or substrate indices would require further research and assessment. Since some epifaunal taxa demonstrate depth preferences, any further research investigating the use of changes in epifaunal taxa distribution as an indicator should incorporate this aspect into the survey design.
• Detection and visual estimation of the percent coverage of Beggiatoa-like bacteria and OPCs from video segments becomes less accurate and precise as their percent coverage decreases. Continuous video segments or increasing the number of frames assessed may increase the accuracy and precision.
• While technological improvements have been made in recent years, advice on methods to visually monitor organic enrichment from finfish aquaculture summarized in Wildish et al. (2005) remain applicable. Further consideration of integrating technological advances, such as additional geo-referencing data, to improve the location of the ROV position during surveys is recommended.

This Science Advisory Report is the product of a national science peer review meeting on the effects of aquaculture activities on hard seabed ecosystems and advice on monitoring protocols held in Vancouver, B.C., March 1-2, 2016. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Scheduleas they become available.

Science Advisory Report 2021/038 (PDF, 537 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.