Presentation: State-of-Knowledge Initiative for the Special Committee on Sustainable Aquaculture of the British Columbia Legislature

Delivered November, 2006.

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Executive Summary

[A full pdf copy for printing may be downloaded from the WAVES database.]

Fisheries and Oceans Canada (DFO) has prepared this report on scientific research related to the environmental interactions between finfish aquaculture and aquatic ecosystems for the Special Committee on Sustainable Aquaculture of the British Columbia Legislature.

DFO is the lead federal agency for aquaculture in Canada, and is committed to well-informed and scientifically-based decisions pertaining to the aquaculture industry.

The public may rightly be confused when they hear or read of ‘warring science’. However, differences in scientific perspectives are certainly not unusual during the development of new knowledge. It can be expected and is healthy for the development of sound scientific knowledge. Sound scientific research requires sound design and implementation, verified through peer review. DFO will continue to evaluate all sources of information in formulating its scientific advice.

Over the past 30 years, DFO has been involved in a wide range of aquaculture-related research programs across the country, including three laboratories in British Columbia. DFO scientists have been recognized for their advances in many areas of finfish and shellfish aquaculture research and development. Much of this work is done collaboratively with academia, other levels of government, industry and scientists from other countries.

A major focus of DFO research has been to determine factors that pose a risk to the health of aquatic ecosystems. To conserve and protect wild salmon, DFO looks at questions that impact the ecosystem as a whole, including: living resources, the aquatic environment, interaction between species, the impact of human activities and many other factors.

DFO has recently published nine State-of-Knowledge Reports that examine the potential environmental effects of aquaculture. Three additional reports are about to be published.

This presentation focuses on areas of primary interest to the Special Committee. Summary reports prepared by DFO scientists working in the Pacific Region are provided on selected research topics including fish health, nearfield interactions and DEPOMOD, farfield and ecosystem interactions, and five components of research on sea lice and interactions with wild salmon.

Key points are summarized below:

Fish Health Research

• The introduction of intensive finfish mariculture in Canada raised concerns of detrimental disease interactions with wild fish.
• Mechanisms are in place to prevent introduction or transfer of fish pathogens.
• No exotic diseases have been introduced to B.C.’s finfish populations.
• There is no evidence that fish farming has contributed to adverse changes in wild fish populations.

Nearfield Interactions and DEPOMOD

• Impacts on the benthic faunal community in the immediate vicinity of net pens have been studied.
• The degree of impact is linked to many factors besides waste loads.
• Models such as DEPOMOD can be useful tools for the management and study of impacts.
• DFO, B.C. Ministry of Agriculture and Lands (MAL) and the industry use DEPOMOD to assist in farm siting and configuration decisions.

Farfield and Ecosystem Interactions

• Farfield effects of fish farming involve broad-scale changes associated with sedimentation, eutrophication and ecosystem interactions.
• Empirical studies and modelling serve as research and monitoring tools related to sedimentation.
• Studies in B.C. demonstrate correlations between physical, chemical and biological characteristics along seafloor gradients at distances of 1 to 5 km from farm sites.
• DFO has established a working group to focus on ecosystem-based research related to aquaculture.

Biology of Pink salmon

• Pink salmon have greater variability in adult returns due to their fixed two-year life history and naturally high juvenile mortality.
• Early research (1961-63) estimated mortality of pink juveniles of 59-77% during the first 40 days in the sea; and total mortality to adults of 89.8% to 98.9% (i.e., survival of 1.1% to 10.2%).
• During the past five years, we have observed both exceptionally poor (2002) and good (2004) returns to the Broughton Archipelago.(BA)
• We need, however, to be aware of returns to specific rivers as well as total returns to the BA.

Biology of Sea Lice

• It is essential to recognize that two species of sea lice (Lepeophtheirus salmonis & Caligus clemensi) are common on salmonids and other fishes in B.C.
• Free-living planktonic larvae of L. salmonis are infective to fish for approximately one week but their survival and infectivity depends highly on temperature and salinity.
• Planktonic larvae have several adaptations to locate suitable hosts. These adaptations are critical as larvae are non-feeding and use only stored energy.
• Although L. salmonis is commonly called the “salmon louse” it is now known to infect non-salmonids, including marine sticklebacks in the Broughton. However, L. salmonis only seems to develop to the pre-adult stage on sticklebacks.

Environmental Conditions in the Broughton Archipelago (BA)

• Currents in the BA region are driven by tides, river discharges, and winds.
• Notable circulation features of the BA include surface “estuarine flows” (seaward flow of low-salinity surface water) and deeper return flows of marine waters. Surfaces flows are determined seasonally by river flow (snow and rain based) and glacial runoff.
• DFO has developed a numerical model describing tidal and surface circulation, but the model is limited by sparse wind observations (being addressed).
• The numerical model has been used to simulate the transport of passive particles released at several salmon farm locations. These simulations generally show seaward transport within several days.
• The consistency of sea lice observations in proximity to farm locations (shown by Krkosek papers) is inconsistent with the DFO model; these differences remain to be resolved through research that was initiated in 2006.

Salmon farms, Sea Lice and Wild Salmon

• In areas of coastal B.C. outside of the BA, the prevalence of L. salmonis is generally less than 5% with low infection intensity. Infection tends to increase offshore as salinity and size of the hosts increases (no information for lower Johnstone Strait and upper Strait of Georgia included).
• The origin of sea lice in the BA is presently inferred from sampling programs and analyses by Krkosek et al. These researchers report a “striking consistent” pattern of increased infection near the location of salmon farms, in 2003 to 2005.
• This consistency of pattern reported by these authors is not, however, evident from extensive independent DFO surveys conducted in the same time and area.
• Research concerning the impact of sea lice infection on individual juvenile salmon differs presently between studies conducted within the BA and those at the Pacific Biological Station. Differences between field and laboratory studies are not uncommon, but this issue remains to be resolved.
• While DFO has increased monitoring of pink and chum salmon returns, the results currently do not confirm or support a direct association between sea lice infection levels on juveniles and subsequent adult returns.

Managing Risk and Sustaining wild Pacific Salmon Populations

• Concern about salmon farms, sea lice, and juvenile salmon in the BA is ultimately about sustainability of wild salmon populations and their ecosystems. DFO’s Strategic Plan and the Wild Salmon Policy (2005) are strong commitments to these conservation values.
• Sustainability of returns in the BA requires that all sources of impact on salmon production be managed, including local impacts of logging or enhancement, fishing impacts, climate-based variation, and salmon farms.
• To-date, management steps taken include the 2003 action plan (fallowing along a prescribed “migration corridor”), and Provincial sea lice management plans since 2004. DFO does not support migration corridors as sufficient actions.
• Chemical treatment with Slice® seems effective for feeding salmon and protects hosts for months depending on temperature. Ecological concerns with treatment, and in particular, for species of interest in B.C. require further research and monitoring.
• DFO also notes the use of regional management plans in other farming jurisdictions (Scotland, Ireland, and Norway).

In Conclusion

Advancement in biological sciences seldom proceeds without opposing perspectives, observations, and hypotheses that are compared and tested before they are resolved.

The knowledge that is gained by explaining these differences can lead to development of new management practices or policies. DFO is involved in extensive research to provide the scientific basis for sustainable management of salmon aquaculture in B.C.