Research Document - 2003/051
Indicators and ‘response’ points for management of fraser river eulachon: a comparison and discussion with recommendations
By Hay, D.E., West, K. and Anderson, A.D.
Abstract
This report reviews potential indicators and response points for the management of eulachons (Thaleichthys pacificus) in the Fraser River. Concern for the conservation of eulachons in the Fraser River peaked in 1994, following poor returns in First Nations and commercial fisheries. This concern prompted field research to estimate spawning biomass and the introduction of fishing closures and other restrictions. Future management and fisheries require explicit management plans based on objective criteria - or ‘indicators’ and ‘response points’ about the status of spawning stock biomass and fisheries. The main indicator is the spawning stock biomass (SSB) estimated annually (since 1995) from egg and larval surveys. With such a short time series, we were not able to develop quantitatively explicit response points based on population dynamic models. Instead, for the SSB and other indicators defined in this paper, we propose and define several ‘response’ points that we suggest are both precautionary and biologically realistic. For instance, as a response point for the SSB indicator, we explain why a SSB of less than 150 tonnes, for 2 consecutive years, could be a response point for conservation. Another indicator is an offshore index of abundance of eulachons estimated during annual shrimp trawl surveys in May. Offshore biomass estimates include two cohorts from the Fraser and Columbia Rivers. An offshore biomass estimate of less than 1000 tonnes in offshore waters could be a response point for concern about Fraser River eulachon fisheries. Another indicator is catch data from Columbia River fisheries. Columbia River eulachon spawn mainly in January and February, about four months earlier than Fraser River eulachons. In most years, a cumulative annual catch of less than 500 tonnes in the Columbia could be cause for conservation concern, and therefore a response point, for the spawning run in the Fraser River. Test fishery data, collected for seven years since 1995 provides a potential response point that may be useful for ‘inseason’ management decisions. The utility of these test fishery data as an indictor, however, remains to be demonstrated. The comparison of test fishery catches with SSB estimates is promising but yet not convincing. Nevertheless, we discuss some potential response points related to test fishery data. We suggest that there are no firm biological criteria, or sufficient biological information to set a ‘biological’ quota, but the long term catch history of the Fraser has often seen catches in excess of several hundred tonnes. We do not recommend such catch levels be set at the present time but point out that annual catch levels in the commercial fishery since 1980 have been about 20 tonnes, for a total removal of about 30 tonnes. The combined removals from other sources (First Nations and recreational catches) may have been another 10 tonnes (although this last estimate is very rough). Therefore under normal conditions the Fraser River probably has a spawning biomass of about 500-1000 tonnes so removal of 30 tonnes would constitute an annual catch rate about three to six percent. We suggest that such a removal is sustainable. An unresolved issue, beyond the scope of the present paper, is the potential removal of Fraser River eulachons as bycatch in offshore trawl fisheries.
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