Managing Atlantic salmon (Salmo salar L.) in the mixed stock environment: challenges and considerations

Abstract

2003. Managing Atlantic salmon in the mixed stock environment: challenges and considerations. e ICES Journal of Marine Science, 61: 1344e1358.Atlantic salmon, as a result of their population structure and behaviour, are potentially subject to a complex array of fisheries, ranging from those within rivers harvesting single stocks, to distant-water mixed stock fisheries that harvest fish from different countries, stock complexes, and continents. In addition, estuarine and in-river fisheries may catch fish from more than one stock or stock component, where these are present. One of the main challenges in managing salmon across this range of fisheries is to account for the differing status of stocks with respect to safe biological limits, noting that stocks of differing productivity may require different harvest strategies. Also, the existence of sequential harvest in different fisheries provides unique challenges, because decisions in an individual fishery cannot be made in isolation of the impacts of other fisheries on those stocks. We illustrate the uncertainties and complexities involved in managing mixed stocks of salmon, whether in homewaters or in distant-water fisheries, and examples are given to illustrate how science and management are, or should be, developing to face these challenges.

Genetic mixed stock analysis of an interceptory Atlantic salmon fishery in the Northwest Atlantic

“…Interceptory fisheries represent an ongoing challenge to fisheries management as stock specific composition and exploitation information are often lacking (Chase, 2003;Crozier et al, 2004;Saunders, 1981;Utter and Ryman, 1993). In the short term, these fisheries can threaten the persistence of depressed or endangered stocks and ultimately can erode intraspecific diversity (Hilborn et al, 2003;Schindler et al, 2010).…”

“…of rare constituents as the stock composition of mixed harvests are often unknown (Crozier et al, 2004;Saunders, 1981). A variety of approaches have been used to disentangle the composition of mixed stock fisheries including the application of physical tags (Candy and Beacham, 2000;Reddin et al, 2012;Weitkamp and Neely, 2002), morphometric analysis (e.g., Reddin and Friedland, 1999;Shepard et al, 2010), geochemistry (Campana et al, 1999;Fraile et al, 2015;Jónsdóttir et al, 2007), and molecular genetic approaches (Araujo et al, 2014;Ensing et al, 2013;Ruzzante et al, 2000).…”

Portfolio theory as a management tool to guide conservation and restoration of multi‐stock fish populations

“…However, in Lake Erie walleye, anthropogenic stressors such as harvest and habitat modification may have disproportionate negative effects on river stocks relative to the open-lake stock, causing a deficiency in naturally developed portfolio effects. This type of deficiency leaves a population with complex stock structure susceptible to continued exploitation, natural fluctuations in regional weather patterns as well as the unpredictable effects of climate change (Smedbol and Stephenson 2001, Hilborn et al 2003, Crozier et al 2004, Carlson and Satterthwaite 2011. Fortunately, when sufficient data are available, portfolio theory offers a framework for quantifying the relationships among stocks that can lead to better-informed management of multi-stock populations such as Lake Erie walleye.…”

“…Although the results of these efforts remain uncertain, facilitated barrier passage on other Lake Erie tributaries, such as the Grand River, Ontario, have led to increased stock-specific recruitment and spawner abundance (MacDougall et al 2007), providing optimism for the riverine stocks discussed herein. Additionally, recognition of stock dynamics and management at ecologically relevant scales (e.g., individual stocks) could help reduce the potential for stockspecific overharvest and loss of stock diversity (Stephenson 1999, Crozier et al 2004, Hutchinson 2008. Therefore, with our portfolio analysis setting a baseline and continued stock specific monitoring, we will be able to evaluate the success of continued riverine rehabilitation and guide future efforts.…”

Effect of demography on spatial distribution: movement patterns of the Albemarle Sound–Roanoke River stock of Striped Bass (Morone saxatilis) in relation to their recovery

“…Accordingly, future research should establish the productivity of the AR stock of Striped Bass in relation to other stocks. If the AR stock is found to be less productive, then future work also should determine the implementation costs of more stringent fi shing regulations in the mixed stock fi shery, namely the amount and value of harvest that would be lost from more productive stocks (Chaput, 2004;Crozier et al, 2004;Hilborn et al, 2004).…”