Indicators and

Indicators and "Response" Points for Management of Fraser River Eulachon: Protocols for Managing a Data-Limited Fishery

D.E. Hay, K. West, A.D. Anderson, and D. Rutherford

Indicators and This is part of Fisheries Assessment and Management in Data-Limited Situations
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Description

Future management of eulachon fisheries (Thaleichthys pacificus) in the Fraser River requires a management plan based on objective criteria. Ideally such criteria would be based on biological indicators and for each indicator there may be an explicit “reference” point that triggers a management decision. Usually reference points are determined from an understanding of population dynamics of a species. The main indicator for Fraser River eulachon is the spawning stock biomass (SSB) estimated annually since 1995 from egg and larval surveys. With such a short time series, we could not define explicit reference points based on population dynamic models. Instead, for the SSB and other indicators, we defined several "response" points. These response points are based on our judgment about the reliability of indicators that we think are precautionary and biologically realistic. We present these response points in the context of a "traffic light" scenario where, for example, an SSB of less than 150 t, for 2 consecutive years would represent a red light and fishing would not occur. A second indicator is an off shore eulachon biomass index estimated during annual shrimp trawl surveys in May. A biomass estimate of less than 1,000 t in off shore waters is a response point (yellow light) for concern about Fraser River eulachon fisheries. Another indicator is the assessment of the spawning run and catch data from the Columbia River fishery which occurs about 4 months prior to the fishery in the Fraser. A poor run or low catch in the Columbia may anticipate low Fraser River catches and could be a response point (yellow light) for the Fraser River. The last indicator is test-fishery data collected since 1995; but the reliability of these data remains uncertain—comparison of test-fishery catches with the SSB is promising but not convincing. However, these data provide a reassurance about run strength that may be useful for inseason management decisions. The paper concludes with a discussion of how to reconcile conflicting indicators in the context of the traffic light scenario.

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