Research Document - 2009/080
Review of DFO Science information for Atlantic salmon (Salmo salar) populations in the eastern Cape Breton region of Nova Scotia
By A.J.F. Gibson and H.D. Bowlby
Abstract
The purpose of this document is to provide background information on Atlantic salmon in the eastern Cape Breton region (Salmon Fishing Area 19) of Nova Scotia in support of a review of the status of Atlantic salmon populations in eastern Canada by the Committee on the Status of Endangered Wildlife in Canada. There are 30 rivers with reported Atlantic salmon catches within SFA 19, although salmon may be or may have been present in other smaller streams in the region. Salmon populations on the east side of the Bras d’Or Lakes generally inhabit lower gradient streams and mature at a younger age than salmon populations on the west side of the lakes, suggesting that there may be some genetic structuring among populations within this region.
Salmon population monitoring in eastern Cape Breton is focused on five river systems: Middle, Baddeck, North, Grand and Clyburn. Assessments in these rivers are based on recreational catches, as well as fishery-independent counts of salmon by diver surveys, except in Grand River where only recreational catch data are used at present. An index-based assessment model for the Middle and Baddeck populations is used for the first time in this assessment. Of these five populations, two (Grand and Clyburn) show marked declines in adult abundance over the last 15 years and a third (North) has declined significantly over the last 20 years. The other two populations (Middle and Baddeck) appear to be more or less stable but at abundance levels well below their conservation requirements. Only one population (North) is estimated to be above its conservation requirement.
Status of salmon in other rivers is based on recreational catch data and intermittent electrofishing surveys. In recent years, reported recreational fishing effort has been concentrated on the North, Baddeck and Middle rivers and has remained relatively unchanged on the rivers where salmon are known to occur. These observations could indicate that abundance is low in most other rivers. This result is consistent with the electrofishing data which shows that juvenile salmon abundance is not high at many locations, even though juvenile salmon are still widely distributed in eastern Cape Breton. Overall, the status of salmon populations in SFA 19 with respect to extinction risk is uncertain, although abundance tends to be low. This conclusion is consistent with the geographic location of these populations. To the south is the Southern Uplands where declines are ongoing and river-specific extirpations have occurred, and to the west in western Cape Breton and the Gulf of St. Lawrence where abundance in at least some populations is increasing.
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