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1. Non-linearity in stock–recruitment relationships of Atlantic cod: insights from a multi-model approach

   https://doi.org/10.1093/icesjms/fsz113  

   Sguotti, Camilla; Otto, Saskia A; Cormon, Xochitl; Werner, Karl M; Deyle, Ethan; Sugihara, George; Möllmann, Christian (June 2019, ICES Journal of Marine Science)

   Griffith, Gary (Ed.)

   Abstract The stock–recruitment relationship is the basis of any stock prediction and thus fundamental for fishery management. Traditional parametric stock–recruitment models often poorly fit empirical data, nevertheless they are still the rule in fish stock assessment procedures. We here apply a multi-model approach to predict recruitment of 20 Atlantic cod (Gadus morhua) stocks as a function of adult biomass and environmental variables. We compare the traditional Ricker model with two non-parametric approaches: (i) the stochastic cusp model from catastrophe theory and (ii) multivariate simplex projections, based on attractor state-space reconstruction. We show that the performance of each model is contingent on the historical dynamics of individual stocks, and that stocks which experienced abrupt and state-dependent dynamics are best modelled using non-parametric approaches. These dynamics are pervasive in Western stocks highlighting a geographical distinction between cod stocks, which have implications for their recovery potential. Furthermore, the addition of environmental variables always improved the models’ predictive power indicating that they should be considered in stock assessment and management routines. Using our multi-model approach, we demonstrate that we should be more flexible when modelling recruitment and tailor our approaches to the dynamical properties of each individual stock. 

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2. Sixty-five years of northern anchovy population studies in the southern California Current: a review and suggestion for sensible management

   https://doi.org/10.1093/icesjms/fsaa004  

   Sydeman, William J; Dedman, Simon; García-Reyes, Marisol; Thompson, Sarah Ann; Thayer, Julie A; Bakun, Andrew; MacCall, Alec D; Hunsicker, Mary (February 2020, ICES Journal of Marine Science)

   Abstract The central stock of northern anchovy (CSNA; Engraulis mordax), the most abundant small pelagic fish in the southern California Current, is key to ecosystem functions. We review drivers of its population dynamics in relation to management. Springtime upwelling intensity lagged by 2 years co-varied positively with CSNA biomass, as did the abundance of Pacific sardine (Sardinops sagax; weakly negative). CSNA population dynamics indicate the need for a multi-species stock assessment, but given serious challenges with modelling population collapse and recovery dynamics, and its moderate fisheries, we suggest that sensible management could be a simple 2-tier harvest control rule designed to emphasize the key trophic role of CSNA in the ecosystem while maintaining moderate socio-economic services. We recommend a monitoring fishery of no more than 5 KMT year−1 split between central and southern California when the stock falls below the long-term median abundance estimate of 380 KMT across the California portion of its range, and a catch limit of 25 KMT year−1 when the stock is above this reference point. This rule would be precautionary, serving to maintain the most important small pelagic forage in the ecosystem, various fisheries interests, and information streams when the population is in a collapsed state. 

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3. Abalone populations are most sensitive to environmental stress effects on adult individuals

   https://doi.org/10.3354/meps13320  

   Aalto, EA; Barry, JP; Boch, CA; Litvin, SY; Micheli, F; Woodson, CB; De Leo, GA (June 2020, Marine Ecology Progress Series)

   null (Ed.)

   Marine organisms are exposed to stressors associated with climate change throughout their life cycle, but a majority of studies focus on responses in single life stages, typically early ones. Here, we examined how negative impacts from stressors associated with climate change, ocean acidification, and pollution can act across multiple life stages to influence long-term population dynamics and decrease resilience to mass mortality events. We used a continuous-size-structured density-dependent model for abalone ( Haliotis spp.), calcifying mollusks that support valuable fisheries, to explore the sensitivity of stock abundance and annual catch to potential changes in growth, survival, and fecundity across the organism’s lifespan. Our model predicts that decreased recruitment from lowered fertilization success or larval survival has small negative impacts on the population, and that stock size and fishery performance are much more sensitive to changes in parameters that affect the size or survival of adults. Sensitivity to impacts on subadults and juveniles is also important for the population, though less so than for adults. Importantly, likelihood of recovery following mortality events showed more pronounced sensitivity to most possible parameter impacts, greater than the effects on equilibrium density or catch. Our results suggest that future experiments on environmental stressors should focus on multiple life stages to capture effects on population structure and dynamics, particularly for species with size-dependent fecundity. 

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4. Global trade network patterns are coupled to fisheries sustainability

   https://doi.org/10.1093/pnasnexus/pgad301  

   Elsler, Laura G.; Oostdijk, Maartje; Gephart, Jessica A.; Free, Christopher M.; Zhao, Junfu; Tekwa, Eden; Bochniewicz, Elaine M.; Giron-Nava, Alfredo; Johnson, Andrew F.; Liu, ed., Junguo (September 2023, PNAS Nexus)

   Abstract The rapid development of seafood trade networks alongside the decline in biomass of many marine populations raises important questions about the role of global trade in fisheries sustainability. Mounting empirical and theoretical evidence shows the importance of trade development on commercially exploited species. However, there is limited understanding of how the development of trade networks, such as differences in connectivity and duration, affects fisheries sustainability. In a global analysis of over 400,000 bilateral trade flows and stock status estimates for 876 exploited fish and marine invertebrates from 223 territories, we reveal patterns between seafood trade network indicators and fisheries sustainability using a dynamic panel regression analysis. We found that fragmented networks with strong connectivity within a group of countries and weaker links between those groups (modularity) are associated with higher relative biomass. From 1995 to 2015, modularity fluctuated, and the number of trade connections (degree) increased. Unlike previous studies, we found no relationship between the number or duration of trade connections and fisheries sustainability. Our results highlight the need to jointly investigate fisheries and trade. Improved coordination and partnerships between fisheries authorities and trade organizations present opportunities to foster more sustainable fisheries. 

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5. Pathways for integrating historical information into fisheries decision‐making

   https://doi.org/10.1111/faf.12854  

   McClenachan, Loren; Cope, Jason; Martínez‐Candelas, Ilse; Nowlis, Joshua; Rubio‐Cisneros, Nadia T; Tewfik, Alexander; Cramer, Katie L (August 2024, Fish and Fisheries)

   Abstract Historical information has provided key insights into long‐term ecological change to marine species and ecosystems, with value to fisheries. Yet, pathways to integrate these diverse data sources into fisheries decision‐making have not been clear. Here, we identify an array of biological, ecological, and social information suitable for contemporary science‐based decision‐making, derived from local ecological knowledge, historical archives, archaeological middens and palaeoecological material. We outline two broad pathways to integrate these historical data into fisheries decision‐making, demonstrating that data‐driven use of historical information is relevant across a range of management contexts. First, historical information can inform fisheries assessments that range from simple to complex, affecting indicators of stock status. Second, it can inform estimates of biological potential and social preference, affecting the choice of fisheries reference points. Using the Caribbean Sea as an example, we illustrate these ideas with case studies representing diverse species and historical data types. Integrating historical data can improve indicators of the current state of fish populations and result in management decisions based on a more complete understanding of a potential range of variation, avoiding shifted baselines. The urgency of this work is underscored by accelerating environmental changes and the rapid loss of invaluable historical information sources. By illuminating pathways, our goal is to increase the accessibility of these types of information and to underscore that scientists, managers, and resource users have roles to play in identifying and integrating relevant long‐term data at various spatial and temporal scales to sustainably manage marine fisheries. 

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