Research Document 1997/25

Status of Atlantic salmon in Salmon Fishing Area 21 in 1996, with emphasis on the upper LaHave River, Lunenberg Co., Nova Scotia

By P.G. Amiro and E.M. Jefferson

Abstract

The status of Atlantic salmon spawning escapement for 1996 in the LaHave River above Morgan Falls relative to conservation is presented. The status of stocks in other rivers of SFA 21 is inferred from reports of recreational catches and a distribution of probable angling exploitation rates estimated for the LaHave River. Non-return fallback at Morgan Falls is estimated at about 40% and its impact on the assessment of the status of the stock is reviewed. A count-based estimate of the production of wild smolts above Morgan Falls in 1996 indicated about 20,650 or 0.79 smolts per 100 m². Egg deposition above Morgan Falls in 1996 was 94% of the conservation objective of 1.96x10⁶ without non-return fallback and 56% if non-return fallback was 40%. The modal deposition for the entire LaHave River basin was 75.5% of the basin-wide required conservation escapement of fish and 80% of the basin-wide required deposition of 4.74x10⁶ eggs. The most probable pre-fishery abundance for eleven other rivers of SFA 21 was 7,368 salmon (6,087 - 9,608; 5^th and 95^th percentiles) and the most probable spawning escapement for these rivers was 4,861 fish, a 16% increase from 1995. Status of stocks for SFA 21 rivers is uncertain because of acidification resultant of acid precipitation and the undetermined effectiveness of standard conservation requirements. Egg depositions to the entire LaHave river increased in 1996 because of increased returns to the river, hook-and-release angling and sizes of fish-at-age. The 1996 LaHave River angling catch rate was 44% and exploitation was 30%. Forecasts to Morgan Falls for 1997 indicated a deficit above Morgan Falls assuming a hook-and-release fishery for salmon (>63 cm) and retention of grilse (a 63 cm) below Morgan Falls if non-return fallback at Morgan Falls is 40%. However, escapements may be in excess of spawning requirements below Morgan Falls in 1997, if returns are as forecast and exploitation is as in 1996. Risk to conservation at various exploitation rates for the 1997 returns was estimated. Return rate of hatchery smolts slightly improved in 1996. Short-term prognosis for the LaHave River was favourable with reduced exploitation warranted to improve opportunity for recovery to higher returns.

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