Data‐poor stock assessment of fish stocks co‐exploited by commercial and recreational fisheries: Applications to pike Esox lucius in the western Baltic Sea

Abstract

The management of mixed-use fisheries, that is fisheries that are co-exploited by commercial and recreational fishers, poses many challenges. For instance, commercial and recreational fisheries often have different management objectives (Ahrens et al., 2020;Arlinghaus et al., 2019), and the differences in goals and behaviours increase with the diversity of stakeholders (Mardle et al., 2004;Pascoe et al., 2009). The sustainable management of mixed-use fisheries requires monitoring and managing both its commercial and recreational components, because the combined action of both sectors is responsible for the total fishing mortality induced on a stock

Corroborating age with oxygen isotope profiles in otoliths: consequences for estimation of growth, productivity and management reference points in northern pike (Esox lucius)in the southern Baltic Sea

“…In areas with co-exploitation of stocks by commercial and recreational fisheries (as in the lagoon fishery around Rügen), both biomass and catch rate/trophy fish size related objectives are jointly relevant (Gemert et al, 2022), and compromises have to be reached between competing objectives (Ahrens et al, 2020). Using an integrated multi-objective utility function, we found that scale-informed models would favor a higher optimal minimum-length limit (around 80 cm) compared to models informed by otoliths or corroborated age(around 75 cm).…”

“…The current minimum-length limit for pike in the Rügen lagoons of 50 cm was used as default for assessing fisheries reference points. To mimic impacts of the growth models on future policies, we varied the minimum-length limit as a common harvest regulation measure between 50 and 100 cm in steps of 1 cm among model simulations with F fixed at 0.2 year -1 , representing the current fishing pressure estimated from stock assessment (Gemert et al, 2022). The one minimum-length limit maximizing the log-utility function composed of the five objectives mentioned above was defined as optimal and could be interpreted as the best compromise among multiple management objectives as in Ahrens et al (2020).…”

“…These data are particularly rare in inland and small-scale coastal fisheries that lack resources for annual monitoring (Beard et al, 2011; Brownscombe et al, 2019; Midway et al, 2016; Post et al, 2002). One example where severe data gaps exist are coastal fisheries in the southern Baltic Sea, such as the fisheries targeting the freshwater species northern pike ( Esox lucius , Linnaeus 1758) in brackish environments (Gemert et al, 2022).…”

Digital fisheries data in the Internet age: Emerging tools for research and monitoring using online data in recreational fisheries

“…declining or increasing) rather than absolute population status. Leveraging digital fisheries data can be useful for data‐poor fisheries where assessment and management are constrained (Arlinghaus & Krause, 2013; Pilling et al, 2009), or to supplement traditional stock assessments that may not have historical context to draw on (van Gemert et al, 2022). Analog analogues of digital fisheries data illustrate how access to historic records can provide information to fisheries management where digital fisheries data are too new to provide suitable examples.…”

“…cal context to draw on(van Gemert et al, 2022). Analog analogues of digital fisheries data illustrate how access to historic records can provide information to fisheries management where digital fisheries data are too new to provide suitable examples.…”