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Case Study 3, Approach 3, Analysis of alternative, river specific reference points

Objective

This approach involves the calculation of separate MSY-based reference points (or conservation limits, CL) for 15 wild Atlantic salmon (Salmo salar) stocks within the Baltic Sea. These reference points provide a management alternative to the previous IBSFC reference points based on 50% of the remaining smolt production capacity.

Results

The recent progress regarding this approach has been described in the latest report of the Baltic Salmon and Trout Assessment Working Group (WGBAST 2007; section 5.6). A paper by Michielsen et al. is ready to be submitted:

Michielsens, C.G.J., Dahl, J., Romakkaniemi, A., Pulkkinen, H., Karlsson, L. and Mäntyniemi, S. Precautionary biological reference points for Atlantic salmon (Salmo salar) stocks within the Baltic Sea.
Abstract: This paper presents the calculation of limit reference poins (or conservation limits, CL) for 15 wild Atlantic salmon (Salmo salar) stocks within the Baltic Sea. These fishery reference points are analytically derived from the stock-recruit parameters for these stocks after converting the egg to smolt relationships into spawner to spawner relationships. The paper also illustrates the impact of uncertainty caused by future M74 outbreaks, causing high mortality among salmon juveniles, when determining precautionary reference points for these stocks. Following the precautionary approach, the exploitation of the mixed offshore fishery should be based on the weakest stocks with the lowest resilience to exploitation, i.e. the stock located in the southern Baltic Sea. Because these stocks are not exploited by the coastal mixed stock fishery in the Gulf of Bothnia, a separate precautionary reference point can be set for this fishery based on the weakerst stock affected by this fishery, i.e. the river Simojoki. For the remaining stocks, individual precautionary reference points can be set for the river fisheries. These new limit reference points require more restrictions on exploitation than in case of the previous IBSFC reference points based on 50% of the smolt production capacity. With the exceptions of the stocks in the rivers Tornionjoki and Mörrumsån, salmon production in most rivers is likely below optimum production levels.

Dissemination and References

Michielsens, C.G.J., Dahl, J., Romakkaniemi, A., Pulkkinen, H., Karlsson, L. and Mäntyniemi, S. Precautionary biological reference points for Atlantic salmon (Salmo salar) stocks within the Baltic Sea. (to be submitted).

 
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