Research Document - 2003/121

Densities of juvenile Atlantic salmon (Salmo salar) in inner Bay of Fundy rivers during 2000 and 2002 with reference to past abundance inferred from catch statistics and electrofishing surveys

By Gibson, A.J.F., Amiro, P.G., Robichaud-Leblanc, K.A.

Abstract

Inner Bay of Fundy (iBoF) Atlantic salmon are presently listed as endangered by COSEWIC. During 2002, an extensive electrofishing survey was undertaken to estimate the abundance of juvenile Atlantic salmon in iBoF rivers. Five organizations (the Department of Fisheries and Oceans, the Nova Scotia Department of Agriculture and Fisheries, Fort Folly First Nation, the University of New Brunswick and Parks Canada) electrofished a total 117 sites in 36 iBoF rivers in 2000 and a total of 246 sites in 43 iBoF rivers in 2002. In 2000, during the first pass of these surveys, a total effort of c. 87,000 seconds of shocking time was applied over c. 79,000 m² of habitat, resulting in the capture of 7,091 fish including 557 Atlantic salmon. In 2002, during the first pass of these surveys, a total effort of c. 157,000 seconds of shocking time was applied over c. 136,000 m² of habitat, resulting in the capture of 10,371 fish including 1,956 Atlantic salmon. Of 34 rivers without live gene bank (LGB) support, fry were not found in 30 of these rivers and parr were absent in 22. Where salmon were present in rivers without LGB support, mean densities of fry and parr were low relative to past surveys. Mean densities of fry and parr in each New Brunswick iBoF river were less than 5.2 and 3.8 fish per 100 m². In Nova Scotia iBoF rivers, fry were totally absent and mean densities of parr were less than 7.1 fish per 100 m². At this time, estimates of densities of wild juvenile salmon in rivers with LGB support are confounded by the presence of captive-reared fish, although densities are also low at sites within these rivers that are distant from LGB release sites.

The results of this survey are placed in context by comparison with results of previous electrofishing surveys and catches in the recreational fishery. These comparisons, together with the analyses of temporal trends for the Stewiacke and Big Salmon rivers, clearly indicate that the decline is not limited to just a few rivers. Data collected during the last few years indicate that the decline in abundance that lead to the listing of this complex by COSEWIC is continuing.

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