Small-Scale Vertical Movements of Summer Flounder Relative to Diurnal, Tidal, and Temperature Changes

Observation of animal movements on small spatial scales provides a means to understand how large-scale species distributions are established from individual behavioral decisions. Small-scale vertical movements of 14 Summer Flounder Paralichthys dentatus residing in Chesapeake Bay were observed by using depth data collected with archival tags. A generalized linear mixed model was employed to examine the relationship between these vertical movements and environmental covariates such as tidal state, time of day, lunar phase, and temperature. Vertical movements increased with warming water temperatures, and this pattern was most apparent at night and during rising and falling tides. Fish generally exhibited greater vertical movements at night, but the difference between vertical movements in the day and those at night decreased as fish increased in size. Results from this study fill a void in understanding the small-scale movements of Summer Flounder and could be incorporated into individual-based models to investigate how species distributions develop in response to environmental conditions

Precautionary harvest policies and the uncertainty paradox

Elements of the precautionary approach to fishery management are commonly implemented in the form of harvest control rules, with limit, threshold and target reference points for stock size and fishing mortality. However, a review of two large advisory and management systems indicates that many stock assessments are not sufficiently informative to support such control rules. After a nearly a decade of applying such control rules, a large portion of management units in the International Council for the Exploration of the Sea (ICES) convention and marine fisheries under United States jurisdiction still have uncertain status, because many management units lack a complete suite of fishing mortality and biomass estimates and associated reference points. For those fishery resources with analytical stock assessments and reference point estimates, fishing mortality has generally been reduced to within prescribed limits. The number of stocks in the ICES area with excessive fishing mortality (i.e., greater than the limit reference point) decreased since 1997, but the number of stocks in need of rebuilding increased as a result of excessive fishing or revised reference points. The number of U.S. stocks with excessive fishing decreased and the number of stocks needing rebuilding decreased as a result of stock recovery, revised reference points, or redefined management units. The number of U.S. stocks with uncertain or undefined status substantially decreased. The large portion of stocks with uncertain status in both systems illustrates that such precautionary control rules are applied only to data-rich stock assessments, and are not being applied to management of fishery resources with the most uncertain stock assessments

Age validation for goosefish (Lophius americanus) in the northeastern United States

The goosefish (Lophius americanus) supports a valuable commercial fishery in the northeastern United States, but annual catch limits are relatively low because of uncertainty in assumed growth rates used for stock assessment. We evaluated the accuracy of the vertebral aging protocol and explored alternative aging methods by injecting chemical markers into individual goosefish held in the laboratory and tagged and recaptured in the field. The chemical left visible marks on vertebrae, illicia, and otoliths at the time of injection, but visibility and intensity of the marks varied among these aging structures. Times after marking ranged from 185 to 860 d for the 20 fish that were analyzed. Observed and expected counts of annuli after the chemical mark indicate that growth increments on vertebrae do not represent annuli and, therefore, cannot be used to accurately determine the age of goosefish. Identification of presumed annuli after the chemical mark was not possible for otoliths because the mark was not visible in most of the samples. Identification of presumed annuli was better for illicium samples than for vertebral samples. The growth rates of the individuals recaptured in the field provide preliminary information on annual growth of goosefish

2022 ASAP stock assessment of the eastern Atlantic and Mediterranean bluefin tuna

The Age Structured Assessment Program (ASAP) was applied to Eastern Atlantic and Mediterranean Atlantic Bluefin tuna for the 2022 stock assessment. Previous single-fleet applications of ASAP for the 2017 and 2020 Atlantic Bluefin tuna assessments were updated and revised, and alternative models with fleet structure were explored. The single-fleet ASAP runs generally fit the data well, and were retrospectively consistent, but residual patterns in age composition and uncertainty in selectivity parameters could not be resolved. Model estimates suggest a substantial change in selectivity in the late 1990s. Multi-fleet ASAP models were developed to fit catch data and estimate selectivity for each index fleet and the Mediterranean purse seine fleet. Multi-fleet-based runs were also retrospectively consistent and fit the available data well, with some residual patterns, but catch data by fleet need revision. Status determination from single-fleet and provisional multi-fleet runs was similar: The stock recovered over the last decade from strong recruitment and low fishing mortality, the estimate of 2020 fishing mortality was much less than F0.1, and the estimate of 2020 spawning biomass was much greater than SSBF0.1.Le programme d’évaluation structuré par âge (ASAP) a été appliqué au thon rouge de l’Atlantique Est et de la Méditerranée pour l’évaluation du stock de 2022. Les applications précédentes d’ASAP à flottille unique pour les évaluations du thon rouge de l’Atlantique de 2017 et 2020 ont été mises à jour et révisées et des modèles alternatifs avec une structure de la flottille ont été étudiés. Les scénarios de ASAP à flottille unique s'ajustent généralement bien aux données et sont rétrospectivement cohérents, mais les schémas résiduels de la composition par âge et l'incertitude des paramètres de sélectivité n'ont pas pu être résolus. Les estimations du modèle suggèrent un changement substantiel de la sélectivité à la fin des années 1990. Des modèles ASAP pluri-flottilles ont été développés pour ajuster les données de captures et estimer la sélectivité de chaque flottille des indices et pour la flottille des senneurs de la Méditerranée. Les scénarios pluri-flottilles étaient également rétrospectivement cohérents et s’ajustaient bien aux données disponibles avec certains schémas résiduels, mais les données de capture par flottille ont dû être révisées. La détermination de l'état à partir des scénarios à flottille unique et à flottilles multiples provisoires était similaire, à savoir : le stock s'est rétabli au cours de la dernière décennie grâce à un fort recrutement et à une faible mortalité par pêche, l'estimation de la mortalité par pêche en 2020 était bien inférieure à F0,1 et l'estimation de la biomasse reproductrice en 2020 était bien supérieure à SSBF0,1.Se aplicó el Programa de evaluación estructurada por edad (ASAP) al atún rojo del Atlántico este y Mediterráneo para la evaluación de stock de 2022. Se actualizaron y revisaron las aplicaciones previas de ASAP de una sola flota para las evaluaciones de atún rojo del Atlántico de 2017 y 2020, y se exploraron modelos alternativos con una estructura de la flota. En general, los ensayos de ASAP de una sola flota se ajustaron bien a los datos y fueron coherentes desde el punto de vista retrospectivo, pero no se pudieron resolver los patrones residuales en la composición por edad y la incertidumbre en los parámetros de selectividad. Las estimaciones del modelo sugieren un cambio importante en la selectividad a finales de la década de 1990. Se desarrollaron modelos ASAP multiflota para ajustar los datos de captura y estimar la selectividad para cada flota del índice y la flota de cerco del Mediterráneo. Los ensayos basados en múltiples flotas también fueron coherentes desde el punto de vista retrospectivo y se ajustaron bien a los datos disponibles, con algunos patrones residuales, pero los datos de captura por flota necesitan ser revisados. La determinación del estado a partir de ensayos de una sola flota y de múltiples flotas provisiones fueron similares: El stock se recuperó durante la última década gracias a un fuerte reclutamiento y a una baja mortalidad por pesca, la estimación de la mortalidad por pesca de 2020 fue mucho inferior a F0.1 y la estimación de la biomasa reproductora de 2020 fue mucho superior a SSBF0.1

Simulation testing the robustness of stock assessment models to error: some results from the ICES strategic initiative on stock assessment methods

The World Conference on Stock Assessment Methods (July 2013) included a workshop on testing assessment methods through simula- tions. The exercise was made up of two steps applied to datasets from 14 representative fish stocks from around the world. Step 1 involved applyingstockassessmentstodatasetswithvaryingdegreesofeffortdedicatedtooptimizingfit.Step2wasappliedtoasubsetofthestocks and involved characteristics of given model fits being used to generate pseudo-data with error. These pseudo-data were then provided to assessment modellers and fits to the pseudo-data provided consistency checks within (self-tests) and among (cross-tests) assessment models. Although trends in biomass were often similar across models, the scaling of absolute biomass was not consistent across models. Similar types of models tended to perform similarly (e.g. age based or production models). Self-testing and cross-testing of models are a useful diagnostic approach, and suggested that estimates in the most recent years of time-series were the least robust. Results from the simulation exercise provide a basis for guidance on future large-scale simulation experiments and demonstrate the need for strategic investments in the evaluation and development of stock assessment methods.JRC.G.3-Maritime affair

Measuring marine fish biodiversity: temporal changes in abundance, life history and demography

Patterns in marine fish biodiversity can be assessed by quantifying temporal variation in rate of population change, abundance, life history and demography concomitant with long-term reductions in abundance. Based on data for 177 populations (62 species) from four north-temperate oceanic regions (Northeast Atlantic and Pacific, Northwest Atlantic, North mid-Atlantic), 81% of the populations in decline prior to 1992 experienced reductions in their rate of loss thereafter; species whose rate of population decline accelerated after 1992 were predominantly top predators such as Atlantic cod (Gadus morhua), sole (Solea solea) and pelagic sharks. Combining population data across regions and species, marine fish have declined 35% since 1978 and are currently less than 70% of recorded maxima; demersal species are generally at historic lows, pelagic species are generally stable or increasing in abundance. Declines by demersal species have been associated with substantive increases in pelagic species, a pattern consistent with the hypothesis that increases in the latter may be attributable to reduced predation mortality. There is a need to determine the consequences to population growth effected by the reductions in age (21%) and size (13%) at maturity and in mean age (5%) and size (18%) of spawners, concomitant with population decline. We conclude that reductions in the rate of population decline, in the absence of targets for population increase, will be insufficient to effect a recovery of marine fish biodiversity, and that great care must be exercised when interpreting multi-species patterns in abundance. Of fundamental importance is the need to explain the geographical, species-specific and habitat biases that pervade patterns of marine fish recovery and biodiversity