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Impacts of Karenia brevis red tide blooms have been an increasing cause of concern for fisheries management in the Gulf of Mexico (Gulf). The 2019 Gulf red grouper (Epinephelus morio) stock assessment was confronted with the challenges of quantifying and parameterizing red tides during both historical and projection time periods. Red tide mortality was estimated for each age class in the model solely in 2005 and 2014 during severe events. Given the considerable uncertainty surrounding the 2018 red tide and its substantial implications on the status of the population, several projection scenarios were evaluated. Under the assumption of no 2018 red tide mortality, near-term catches were projected to nearly double, a predicted outcome that appeared to be in contrast with recent record low catches and fishing industry perceptions of major stock depletion. In the event that the 2018 red tide caused mortality, but was not accounted for in projections, the recommended catch levels would lead to high probabilities of overfishing and potentially stock collapse. Collectively, these results highlight how consideration of uncertainty in projections can help avoid unintended consequences. Les impacts de marees rouges associees aux proliferations de Karenia brevis sont source d'inquietudes croissantes pour les gestionnaires des peches dans le golfe du Mexique. L'evaluation de 2019 du stock de merous rouges (Epinephelus morio) dans le golfe s'est butee aux defis que constituent la quantification et la parametrisation des marees rouges pour les periodes tant passees que futures projetees. La mortalite associee aux marees rouges a ete estimee pour chaque classe d'age dans le modele uniquement pour 2005 et 2014 durant des episodes de grande intensite. Etant donne l'incertitude considerable entourant la maree rouge de 2018 et ses repercussions importantes en ce qui concerne l'etat de la population, plusieurs scenarios de projection ont ete evalues. Dans l'hypothese qu'il n'y aurait eu aucune mortalite associee a la maree rouge de 2018, il est projete que les prises a court terme doubleraient presque, une prevision que semblent contredire des prises a leur plus bas enregistrees recemment et les perceptions, au sein de l'industrie de la peche, d'un important appauvrissement du stock. Dans l'eventualite que la maree rouge de 2018 ait entrarne une mortalite, mais qu'elle n'ait pas ete prise en consideration dans les projections, les niveaux de prises recommandes se traduiraient en de fortes probabilites de surpeche et, potentiellement, l'effondrement du stock. Collectivement, ces resultats soulignent le fait que la consideration de l'incertitude dans les projections peut aider a eviter des consequences inattendues. [Traduit par la Redaction], Introduction It is widely recognized that the environment influences fish populations--especially as overfishing is reduced--and calls to incorporate the environment as part of an ecosystem approach to fisheries management have [...]

Abstract--The National Marine Fisheries Service conducts fishery stock assessments to provide the best scientific information available for the U.S. regional fishery management councils. The assessment models applied in the United [...]

Specifying annual catch limits for artisanal fisheries, low economic value stocks, or bycatch species is problematic due to data limitations. Many empirical management procedures (MPs) have been developed that provide catch advice based on achieving a stable catch or a historical target (i.e., instead of maximum sustainable yield). However, a thorough comparison of derived yield streams between empirical MPs and stock assessment models has not been explored. We first evaluate trade- offs in conservation and yield metrics for data-limited approaches through management strategy evaluation (MSE) of seven data- rich reef fish species in the Gulf of Mexico. We then apply data-limited approaches for each species and compare how catch advice differs from current age-based assessment models. MSEs identified empirical MPs (e.g., using relative abundance) as a compromise between data requirements and the ability to consistently achieve management objectives (e.g., prevent overfishing). Catch advice differed greatly among data-limited approaches and current assessments, likely due to data inputs and assumptions. Adaptive MPs become clearly viable options that can achieve management objectives while incorporating auxiliary data beyond catch-only approaches. L'etablissement de limites de prises annuelles pour les peches artisanales, les stocks de faible valeur economique ou les especes de prises accessoires pose probleme en raison des donnees limitees sur lesquelles il repose. De nombreuses procedures de gestion (PG) empiriques ont ete elaborees qui fournissent des avis sur les prises bases sur l'atteinte de prises stables ou d'une cible historique (c.-a-d. plutot que le rendement equilibre maximal). Une comparaison exhaustive des differents rendements obtenus de PG empiriques et de modeles devaluation de stock n'a toutefois pas ete effectuee. Nous evaluons d'abord les compromis touchant a la conservation et aux parametres du rendement pour des approches pour donnees limitees par revaluation des strategies de gestion (ESG) de sept especes de poissons recifaux dans le golfe du Mexique pour lesquelles les donnees sont abondantes. Nous appliquons ensuite, pour chaque espece, des approches pour des situations de donnees limitees et comparons les avis sur les prises en decoulant a ceux issus de modeles devaluation actuels bases sur l'age. Les ESG etablissent que les PG empiriques (p.ex. qui utilisent l'abondance relative) constituent un compromis entre les exigences en matiere de donnees et la capacite d'atteindre regulierement les objectifs de gestion (p.ex. la prevention de la surpeche). Les avis sur les prises different considerablement entre les approches a donnees limitees et les evaluations actuelles, vraisemblablement en raison des donnees entrees et des hypotheses sous-jacentes. Les PG adaptatives deviennent des options manifestement viables qui peuvent permettre l'atteinte des objectifs de gestion tout en incorporant des donnees auxiliaires autres que celles qui entrent dans les approches basees uniquement sur les prises. [Traduit par la Redaction], Introduction Nearly 80% of global catch comes from fisheries stocks characterized as lacking formal stock assessments, with less than 1% of species assessed using quantitative approaches due to costs and [...]

Abstract--Commercial fishermen have argued that localized concentrations of spiny dogfish (Squalus acanthias) in the northeast U.S. shelf large marine ecosystem (NES LME) have impeded their fishing operations when monitoring surveys [...]

Increased commercial importance of spiny dogfish (Squalus acanthias) combined with an often debated, and controversial, ecological impact has warranted an investigation of the relationship among distribution, environment, and prey to better understand the species ecology and inform management. To elucidate mechanisms behind distributional changes, we modeled seasonal occurrence and abundance of neonate, immature, and mature spiny dogfish as functions of abiotic and biotic factors using generalized additive models and Northeast Fisheries Science Center bottom trawl survey data. Significant nonlinear relationships were widespread throughout dogfish stages and seasons. Seasonal occurrence was tightly linked to depth and bottom temperature, with year and Julian day influential for some stages. While these factors also influenced abundance, ecological factors (e.g., squid abundances) significantly contributed to trends for many stages. Potential impacts of climate change were evaluated by forecasting distributions under different temperature scenarios, which revealed higher regional probabilities of occurrence for most stages during a warmer than average year. Our results can be used to better understand the relationship between sampling periods and movement drivers to survey catchability of the population in the Northeast (US) shelf large marine ecosystem. L'importance commerciale croissante de l'aiguillat commun (Squalus acanthias), combinee a un impact ecologique controversy faisant l'objet d'un debat soutenu, a motive l'etude du lien entre repartition, milieu et proies dans le but de mieux comprendre l'ecologie de cette espece et d'en eclairer la gestion. Afin de faire la lumiere sur les mecanismes qui sous-tendent les variations de la repartition, nous avons modelise la presence et l'abondance saisonnieres d'aiguillats communs nouveau-nes, immatures et matures en fonction de facteurs abiotiques et biotiques, a l'aide de modeles additifs generalises et de donnees de leves au chalut de fond du Northeast Fisheries Science Center. Des relations non lineaires significatives etaient repandues pour tous les stades de vie de l'aiguillat et toutes les saisons. La presence saisonniere etait etroitement reliee a la profondeur et la temperature au fond, l'annee et le jour julien exerqant une influence pour certains stades. Si ces facteurs influenqaient egalement l'abondance, des facteurs ecologiques (p. ex. l'abondance de calmars) avaient une incidence significative sur les tendances pour de nombreux stades. Les impacts potentiels des changements climatiques ont ete evalues en predisant les repartitions pour differents scenarios de temperature, ce qui a revele des probabilites regionales accrues de presence pour la plupart des stades durant des annees plus chaudes que la normale. Nos resultats peuvent servir a une meilleure comprehension du lien entre les periodes d'echantillonnage et les facteurs influenqant les deplacements dans revaluation de la capturabilite de la population dans le grand ecosysteme marin de la plate-forme du Nord-Est etats-unien., Introduction The Magnuson-Stevens Fishery Conservation and Management Act of the United States emphasizes the integration of ecosystem considerations into assessment methods (Link et al. 2011) consistent with a move towards [...]

Declines in abundance of commercially valuable groundfish have highlighted the ecological and commercial importance of previously underutilized elasmobranchs in the Northeast (US) shelf large marine ecosystem (NES LME). Seasonal distributions and ontogenetic habitats of one such species, spiny dogfish (Squalus acanthias), were investigated using Northeast Fisheries Science Center (NEFSC) bottom trawl survey data (1963-2009). Neonate, immature, and mature dogfish all selected warmer, more saline, and more southerly locations during spring compared with available locations. During autumn, larger dogfish occupied relatively warmer, shallower, and less saline waters while neonates selected higher salinities. There were strong ontogenetic patterns in habitats occupied. Contrary to expectation, geographic range contracted as abundance increased during autumn. This suggests that niche constraints override density-dependent effects, although detection of relationships within stages was limited by low statistical power. The proportion of mature female survey catch within the Mid-Atlantic Bight was significantly related to temperature, suggesting that environmental conditions surveyed may impact population trends. Collectively, these results highlight critical habitats, suggest mechanisms behind ontogenetic habitat selection, and provide insight into how changing environmental conditions may impact stock assessment. Les baisses d'abondance de poissons de fond a valeur commerciale soulignent l'importance ecologique et commerciale d'elasmobranches auparavant sous-utilises dans le grand ecosysteme marin de la plateforme continentale du nord-est des Etats-Unis (NES LME). Les repartitions saisonnieres et les habitats ontogeniques d'une de ces especes, l'aiguillat commun (Squalus acanthias), ont ete examines a la lumiere de donnees de releves au chalut de fond (1963-2009) du Northeast Fisheries Science Center (NEFSC). Parmi les sites disponibles, les aiguillats nouveau-nes, immatures et matures choisissaient tous des emplacements relativement chauds, salins et meridionaux au printemps. A l'automne, les aiguillats plus grands occupaient des eaux relativement chaudes, moins profondes et moins salines, alors que les nouveau-nes choisissaient des eaux de plus forte salinite. L'occupation des habitats definissait des motifs ontogeniques marques. Contrairement aux attentes, l'aire de repartition geographique diminuait parallelement a l'augmentation de l'abondance a l'automne, ce qui donne a penser que les contraintes touchant a la niche l'emportent sur les effets dependants de la densite, bien que la faible efficacite statistique limite la detection de relations pour des stades donnes. La proportion de femelles matures capturees dans le cadre des releves dans le golfe Medio-atlantique etait significativement reliee a la temperature, donnant a penser que les conditions ambiantes pourraient avoir une incidence sur les tendances des populations. Collectivement, ces resultats font ressortir des habitats essentiels et des mecanismes possibles de selection d'habitats ontogeniques et jettent un eclairage sur l'incidence de l'evolution des conditions ambiantes sur l'evaluation des stocks. [Traduit par la Redaction], Introduction Understanding the habitat preferences of marine fishes is important when describing their spatial distribution and ecology (Perry and Smith 1994; Smith and Page 1996; Shepherd et al. 2002) and [...]

The National Marine Fisheries Service conducts fishery stock assessments to provide the best scientific information available for the U.S. regional fishery management councils. The assessment models applied in the United States are often region specific, although the models share similar mathematical and statistical attributes. However, comprehensive comparison studies identifying similarities and differences among these assessment models remain scarce. We developed a multi-model comparison framework to evaluate the reliability of 4 age-structured assessment models that are commonly used in the United States: the Assessment Model for Alaska, the Age Structured Assessment Program, the Beaufort Assessment Model, and Stock Synthesis. When applied to simulated data, all 4 models produced reliable estimates of assessment quantities of interest, such as fishing mortality, spawning biomass, recruitment, and biological reference points. Although there were differences among models in the calculation of the initial population numbers at age and in the bias adjustment of recruitment, their effects on model outputs were minor when estimation models were configured similarly. In addition, we provide guidelines for converting unfished recruitment and steepness between 2 methods of bias adjustment. We recommend that next-generation stock assessment models include recruitment bias adjustment and that more research be conducted to provide guidelines for which methods might be preferred under which situations. [ABSTRACT FROM AUTHOR]

Maintaining fish stocks at optimal levels is a goal of fisheries management worldwide; yet, this goal remains somewhat elusive, even in countries with well‐established fishery data collection, assessment and management systems. Achieving this goal often requires knowledge of stock productivity, which can be challenging to obtain due to both data limitations and the complexities of marine populations. Thus, scientific information can lag behind fishery policy expectations in this regard. Steepness of the stock–recruitment relationship affects delineation of target biomass level reference points, a problem which is often circumvented by using a proxy fishing mortality rate (F) in place of the rate associated with maximum sustainable yield (FMSY). Because MSY is achieved in the long term only if an F proxy is happenstance with FMSY, characterizing productivity information probabilistically can support reference point delineation. For demersal stocks of equatorial and tropical regions, we demonstrate how the use of a prior probability distribution for steepness can help identify suitable F proxies. F proxies that reduce spawning biomass per recruit to a target percentage of the unfished quantity (i.e., SPR) of 40% to 50% SPR had the highest probabilities of achieving long‐term MSY. Rebuilding was addressed through closed‐loop simulation of broken‐stick harvest control rules. Similar biomass recovery times were demonstrated for these rules in comparison with more information‐intensive rebuilding plans. Our approach stresses science‐led advancement of policy through a lens of information limitations, which can make the assumptions behind rebuilding plans more transparent and align management expectations with biological outcomes. [ABSTRACT FROM AUTHOR]

To be as accurate as possible, stock assessments should account for discard mortality in fisheries if it occurs. Three common approaches to modeling discards in assessments are to lump dead discards with landings, treat dead discards as their own fleet, or link them conversely with landings through use of a retention function. The first approach (lumping) implicitly assumes that the selectivity of landings applies also to discards. In many cases, that assumption is false, for example, if discards comprise smaller fish than do landings. The latter two approaches avoid the assumption by modeling discards explicitly with their own selectivity pattern. Here, we examine these approaches to modeling discards. Using a simulation study, we demonstrate that the two approaches to modeling discards explicitly can provide identical results under both static and time-varying conditions. Then, using a stock assessment case study of red grouper Epinephelus morio in the U.S. Gulf of Mexico, we demonstrate that in practice the approaches to modeling discards can provide different outcomes, with implications for the resultant management advice. We conclude by comparing and contrasting the different approaches, calling for more research to elucidate which approach is most suitable under various sources of error typically encountered in discard data. [ABSTRACT FROM AUTHOR]