Research Document - 2000/145
Status of the eulachon Thaleichthys pacificus in Canada.
By D.E. Hay and P.B. McCarter
Abstract
The anadromous eulachon (Thaleichthys pacificus) is a small species of smelt that spawns in the lower reaches of coastal rivers and streams from northern California to the southern Bering Sea. Nearly all eulachon spawning runs have declined from California to south-eastern Alaska in the last 20 years, especially since the mid-1990's. The causes of the declines are uncertain, and this paper reviews and comments on the main suggestions and explanations. Climate change is implicated as a cause of a general decline, but other factors cannot be overlooked, including local habitat alterations and bycatch in commercial trawl fisheries. The decline of eulachons is a concern for many First Nations, for whom the eulachon is of major cultural significance, especially as a source of an important traditional staple called 'grease'. The status of eulachons also concerns fisheries managers and the commercial fishing industry because eulachons are common as bycatch in shrimp trawls in some areas. The decline of eulachons has prompted specific management actions to limit eulachon bycatch, and such actions may reduce potential shrimp catches in some areas. The available biological information on eulachons is fragmentary and previously has not been synthesized into a single document. This paper attempts to pool and summarize the available biological information on eulachons prior to commenting on their biological status. Genetic evidence, which is subject to confirmation, indicates that eulachons constitute a single ESU (evolutionary significant unit) throughout their entire range. Other biological data, including data on meristic analyses and river-specific spawning times indicate that there is substantial local stock structure. This may indicate that although different eulachon stocks are genetically coupled, presumably through straying or mixing, different rivers (or estuaries) probably represent demographically uncoupled stocks. Therefore we point out that probably it is precautionary to assume that stock structure is geographically fine, until shown otherwise. The significance of the genetic data to the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) is that classification applies at the level of the ESU, or a significant part of it. Available evidence suggests that several rivers in the central coast of BC may be extirpated, while others have declined severely. Only the Nass maintains normal or near-normal runs, although the Fraser, while markedly lower in recent decades and especially since 1994, still has regular, but diminished runs. The Columbia River, with the world's largest eulachon run, declined sharply in 1993, and has remained low since. Apparently all runs in California have declined and several runs that once were large have not been seen for more than 20 years. Based on these observations, we suggest that the widespread decline in the southern part of the range warrants a COSEWIC classification of 'threatened' in Canadian waters. We further point out, however, that this status could change rapidly as the abundance of immature eulachons in southern offshore waters is substantially greater in 2000 than in the previous decade. If this offshore abundance is indicative of stronger spawning runs in future years, then the classification of 'threatened' may be too severe. On the other hand, the abundant offshore eulachons appear to be mainly from the 1999-year class, which probably will spawn in 2002, and may not contribute to stronger spawning runs in year 2001. We conclude with a plea for the development and implementation of policy for eulachon management, which will cover issues such as commercial fisheries for eulachons, forest industry interactions, dredging and habitat alteration in spawning areas, pollution of spawning rivers and bycatch in offshore trawl fisheries. In this regard, as a potential policy template, we include a short section of recommendations, modified to suit eulachons, from the recent draft of the DFO 'Wild Salmon Policy' paper.
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