Use of genetic data to assess the uncertainty in stock assessments due to the assumed stock structure: the case of albacore (Thunnus alalunga) from the Atlantic Ocean

Stock assessments can be problematic because of uncertainties associated with the data or because of simplified assumptions made when modeling biological processes (Rosenberg and Restrepo, 1995). For example, the common assumption in stock assessments that stocks are homogeneous and discrete (i.e., there is no migration between the stocks) is not necessarily true (Kell et al., 2004a, 2004b)

New SNP markers in european anchovy and albacore: useful genetic tools for stock delimitation

Peer Reviewe

Update of Albacore tag release-recapture information in the North-Atlantic and Mediterranean for the period 1968-1999

This paper updates and completes the ICCAT database on albacore tag release–recapture from the North Atlantic including the Mediterranean Sea. In this revision French tag release– recapture data from the sixties and seventies is included, as well as additional information obtained from existing bibliography.Le présent document actualise et complète la base de données de l'ICCAT sur le marquage et la recapture de germon de l'Atlantique nord, Méditerranée comprise. Cette révision comporte des données françaises de marquage/recapture des années 1960 et 1970, ainsi que des informations additionnelles extraites de la bibliographie disponible.En el presente documento se actualiza y completa la base ICCAT de datos de marcadorecaptura de atún blanco del Atlántico Norte, incluyendo el Mediterráneo. En esta revisión se incluyen los datos de marcado-recaptura franceses de los años los años sesenta y setenta, así como otras informaciones procedentes de revisiones bibliográficas

A new compilation of stomach content data for commercially-important pelagic fish species in the Northeast Atlantic

There is increasing demand for information on predator–prey interactions in the ocean as a result of legislative commitments aimed at achieving sustainable exploitation. However, comprehensive data sets are lacking for many fish species and this has hampered development of multispecies fisheries models and the formulation of effective food-web indicators. This work describes a new compilation of stomach content data for five pelagic fish species (herring, blue whiting, mackerel, albacore and bluefin tuna) sampled across the northeast Atlantic and submitted to the PANGAEA open-access data portal (www.pangaea.de). We provide detailed descriptions of sample origin and of the corresponding database structures. We describe the main results in terms of diet composition and predator–prey relationships. The feeding preferences of small pelagic fish (herring, blue whiting, mackerel) were sampled over a very broad geographic area within the North Atlantic basin, from Greenland in the west, to the Lofoten Islands in the east and from the Bay of Biscay northwards to the Arctic. This analysis revealed significant differences in the prey items selected in different parts of the region at different times of year. Tunas (albacore and bluefin) were sampled in the Bay of Biscay and Celtic Sea. Dominant prey items for these species varied by location, year and season. This data compilation exercise represents one of the largest and most wide-ranging ever attempted for pelagic fish in the North Atlantic. The earliest data included in the database were collected in 1864, whereas the most recent were collected in 2012. Data sets are available at doi:10.1594/PANGAEA.820041 and doi:10.1594/PANGAEA.826992

Using stock assessment information to assess fishing capacity of tuna fisheries

Abstract Arrizabalaga, H., Restrepo, V. R., Maunder, M. N., and Majkowski, J. 2009. Using stock assessment information to assess fishing capacity of tuna fisheries. – ICES Journal of Marine Science, 66: 1959–1966. In tuna and tuna-like fisheries, there is a need for periodic assessments of fishing capacity to aid management. However, the nature and quantity of data needed to apply conventional methodologies for estimating fishing capacity are not usually available for tuna fisheries. We discuss simple alternative approaches to estimate fishing capacity and related quantities (i.e. capacity utilization, excess capacity, and overcapacity) directly from stock assessment inputs and outputs that are usually available for most tuna (and many other) stocks. Sensitivity analyses are performed to assess the effect of different levels of data aggregation and different assumptions made during the stock assessments on estimates of fishing capacity. Main advantages and disadvantages of the proposed methodologies are also illustrated using stock assessment information from different tuna stocks with different historical developments and trends in fishing mortality

Growth of Mediterranean young-of-the-year bluefin tuna Thunnus thynnus (Scombridae): regional differences and hatching periods

This study analyses growth rates of bluefin tuna young-of-the-year in the Mediterranean. Potential differences in growth rates were examined between years (2013 and 2016) and regions (eastern, central and western Mediterranean). A total of 134 specimens were aged by analysing otolith microstructure. Fish sizes ranged between 14.7 and 57 cm fork length, and estimated ages varied between 45 and 192 days. The annual growth models explained more than 90% of growth variability. The observed differences in the growth rates between 2013 (3.2 mm d-1) and 2016 (2.7 mm d-1) were not significant, whereas the daily growth rate was significantly faster in the eastern region (4.01 mm d-1) than in the western (2.52 mm d-1) and central (2.75 mm d-1) regions. Larval hatching windows were consistent with the known spawning periods but lasted longer than previously reported in the central and eastern regions. In the central region the hatching period showed two peaks in mid-June and mid-July, consistent with previous studies pointing to two distinct spawning pulses. These pulses might be due to the existence of different bluefin tuna contingents spawning at different times, the Mediterranean residents and the Atlantic migrants, but further research is needed to support this hypothesis

Estimating albacore movement rates between the North Atlantic and the Mediterraneal from conventional tagging data

A tag attrition model is fit to albacore tag-recapture data in order to estimate albacore movement rates between the Atlantic and the Mediterranean. The estimated transfer rate from the Atlantic to the Mediterranean is not significantly different from zero, and the estimated annual transfer rate in the opposite direction, under the assumptions of the same catchability and reporting rates is 5,49%. Sensitivity tests to assumed reporting rates and relative catchabilities are performed, and observed lower recovery rates in the Mediterranean may suggest either a lower catchability or reporting rate in this area, that would give an even lower estimate of the transfer rate, which is also supported by information from later tag recaptures of fish tagged in the Mediterranean. The small impact of these transfer rates on stock assessment is discussed and a preliminary assessment of the amount of tagged fish needed in order to get accurate and precise estimates of these low transfer rates is also done by simulating different tagging scenarios.Un modèle de déperdition des marques est ajusté aux données de marquage-recapture du germon afin d’estimer les taux de déplacement du germon entre l’Atlantique et la Méditerranée. Le taux de transfert estimé de l’Atlantique à la Méditerranée n’est pas sensiblement différent de zéro, et le taux de transfert annuel estimé dans la direction opposée, en prenant comme postulat une capturabilité et des taux de soumission de données identiques, s’élève à 5,49%. On a réalisé des tests de sensibilité aux taux de soumission de données supposés et à la capturabilité relative. Les taux de récupération inférieurs observés en Méditerranée suggèrent éventuellement une capturabilité ou un taux de soumission de données plus faible dans cette zone, ce qui donnerait une estimation encore plus faible du taux de transfert. Cela est également appuyé par des informations provenant de récupérations tardives de marques de poissons marqués en Méditerranée. Le faible impact de ces taux de transfert sur l’évaluation du stock est discuté et une évaluation préliminaire du volume de poissons marqués nécessaire pour obtenir des estimations exactes et précises de ces faibles taux de transfert est également réalisée en simulant différents scénarios de marquage.Se ajusta un modelo de tasa de pérdida de marcas a los datos de marcado-recuperación de atún blanco con el fin de estimar las tasas de movimiento del atún blanco entre el Atlántico y el Mediterráneo. La tasa de transferencia estimada del Atlántico al Mediterráneo no se diferencia significativamente de cero, y la tasa de transferencia anual estimada en la dirección opuesta, bajo el supuesto de la misma tasa de capturabilidad y comunicación, es de 5,49%. Se realizaron pruebas de sensibilidad de las tasas de comunicación y capturabilidades relativas supuestas, y las tasas de recuperación inferiores observadas en el Mediterráneo pueden sugerir una tasa de capturabilidad o de comunicación más baja en esta zona, lo que proporcionaría una estimación aún más baja de transferencia, que se ve sustentada por la información de recuperaciones de marcas posteriores de peces marcados en el Mediterráneo. Se discute el bajo impacto de estas tasas de transferencia en la evaluación del stock y también se realiza una evaluación preliminar de la cantidad de peces marcados necesarios para obtener estimaciones precisas y exactas de estas bajas tasas de trasferencia mediante una simulación de diferentes escenarios de marcado

Use of lectins to characterise genetic variability and geographic differentiation in natural populations of Thunnus alalunga (Bonn. 1788)

New tools from cell and molecular biology can be used to implement the knowledge of fish biology and fisheries. In this sense, we suggest that the use of lectins can be an understandable procedure to study population structure of fishes. Lectins are proteins or glycoproteins of nonimmune origin that agglutinate cells and/or precipitate complex carbohydrates. Several lectins behave like blood group antibodies and can be used as specific gene markers. We characterise blood groups of Thunnus alalunga worldwide populations under a population genetics point of view using lectins. Fishes from several populations of Mediterranean Sea, Atlantic, Pacific and Indian Oceans were captured and 5 mL blood was obtained from each fish. Each fish was treated with 8 FITC-labelled lectins. The binding activity of the lectins was detected using a fluorescence assay. Several statistical procedures of populations genetics were employed to analyse genetic variability, geographic differentiation, and genetic distance showing that: i) there is genetic variability within Thunnus alalunga populations, ii) we detect highly significant heterogeneity among populations, and considerable geographic differentiation, iii) Mediterranean population is quite distant of North Atlantic population, iv) North and South Atlantic populations are extremely distant, v) Pacific population is the most distant from the others , vi) Gulf of Guinea and South Atlantic populations are distant, vii) Gulf of Guinea and North Atlantic are proximate, viii) Indian and South Atlantic populations are also proximate.De nouveaux moyens fournis par la biologie cellulaire et moléculaire peuvent servir à appliquer les connaissances sur la biologie et la pêche du poisson. A cet égard, nous suggérons que l'utilisation des lectines peut constituer un processus raisonnable pour étudier la structure des stocks de poisson. Les lectines sont des protéines ou des glycoprotéines d'origine non-immunitaire qui agglutinent les cellules et/ou précipitent les carbohydrates complexes. Plusieurs lectines se comportent comme des anticorps de groupes sanguins et peuvent servir de marqueurs génétiques spécifiques. Nous identifions les groupes sanguins des populations globales de Thunnus alalunga du point de vue de la génétique des populations au moyen de lectines. Des poissons de plusieurs stocks de la Méditerranée, de l'Atlantique, du Pacifique et de l'océan Indien ont été capturés, et 5 ml de leur sang a été prélevé. Chacun de ces poissons a été traité avec des lectines dénommées 8 FITC. L'activité agglutinante des lectines a été détectée au moyen de tests de fluorescence. Plusieurs processus statistiques de génétique des populations ont été employées pour analyser la variabilité générique, la différentiation géographique et l'écartement génétique, d'où: i) il existe une variabilité génétique su sein des populations de Thunnus alalunga, ii) nous détectons un degré très significatif d'hétérogénéité entre les populations, et une différentiation géographique considérable, iii) la population méditerranéenne se démarque assez de la population nordatlantique, iv) les populations du nord et du sud de l'Atlantique sont extrêmement distinctes, v) la population du Pacifique est celle qui se différencie le plus des autres, vi) les populations du golfe de Guinée et de l'Atlantique sud sont distinctes, vii) les populations du golfe de Guinée et de l'Atlantique nord sont proches, viii) les populations de l'océan Indien et de l'Atlantique sud sont également proches.Las nuevas herramientas de biología molecular y celular se pueden utilizar para implementar el conocimiento de la biología de los peces y de la pesca. En este sentido, proponemos la utilización de lectinas como procedimiento comprensible para estudiar la estructura de población de los peces. Las lectinas son proteínas o glucoproteínas de origen no inmune que aglutinan células o precipitan carbohidratos complejos. Muchas lectinas se comportan como anticuerpos de grupos sanguíneos y pueden utilizarse como marcadores genéticos específicos. Hemos identificado grupos sanguíneos de poblaciones de Thunnus alalunga de todo el mundo desde el punto de vista de genética de poblaciones mediante lectinas. Se capturaron peces de varias poblaciones del mar Mediterráneo y de los océanos Atlántico, Pacífico e Índico y se les extrajo 5 mL de sangre a cada uno. Se trató a cada pez con lectinas marcadas con FITC 8. La actividad aglutinante de la lectina se detectó utilizando fluorimetrías. Se emplearon varios procedimientos estadísticos de genética de poblaciones para analizar la variabilidad genética, diferenciación geográfica y distancia genética, que mostraron que: i) existe una variabilidad genética dentro de las poblaciones de Thunnus alalunga; ii) detectamos una heterogeneidad muy significativa entre las poblaciones y una considerable diferenciación geográfica; iii) la población mediterránea se distancia bastante de la población del Atlántico Norte, iv) las poblaciones del Atlántico norte y sur son extremadamente distantes; v) La población del Pacífico es la que presenta una mayor distancia con respecto a las demás; vi) las poblaciones del Atlántico Sur y del Golfo de Guinea son distantes; vii) las poblaciones del Golfo de Guinea y el Atlántico norte son próximas; viii) las poblaciones del Índico y el Atlántico sur también son próximas

Study on the migrations and stock structure of Albacore (Thunnus alalunga) from the Atlantic Ocean and the Mediterranean sea based on conventional tag release-recapture experiences

In this paper a study on the migrations of albacore from the North Atlantic Ocean and the Mediterranean Sea is made, based on the information from conventional tag release-recapture experiences. Information on 643 recaptured fish from a total of 23,777 tagged fish has been analyzed. This information highlights the long distance movements of albacore, their transoceanic migrations and the possibility of an interchange of fish between the North Atlantic and the Mediterranean.Le présent document fait état d'une étude sur les migrations du germon de l'Atlantique nord et de la Méditerranée, d'après des informations provenant d'expériences de marquage et de recapture avec marques conventionnelles. L'information correspondant à 643 poissons recapturés sur un total de 23.777 poissons marqués a été analysée. Cette information révèle les déplacements du germon sur de grandes distances, ses migrations transocéaniques et l'éventualité d'échanges de poissons entre l'Atlantique nord et la Méditerranée.En este documento se hace un estudio de las migraciones del atún blanco del Atlántico norte y Mediterráneo en base a las informaciones procedentes de las experiencias de marcado-recaptura convencionales. Se ha analizado la información procedente de 643 peces recapturados de un total de 23.777 peces marcados. Con esta información se ponen de manifiesto los grandes movimientos del atún blanco, sus desplazamientos transoceánicos y la posibilidad de intercambio de peces entre el Atlántico norte y el Mediterráneo

Testing robustness of CPUE standardization and inclusion of environmental variables with simulated longline catch datasets

Environmental variability changes the distribution, migratory patterns, and susceptibility to various fishing gears for highly migratory marine fish. These changes become especially problematic when they affect the indices of abundance (such as those based on catch-per-unit-effort: CPUE) used to assess the status of fish stocks. The use of simulated CPUE data sets with known values of underlying population trends has been recommended by ICCAT (International Commission for the Conservation of Atlantic Tunas) to test the robustness of CPUE standardization methods. A longline CPUE data simulator was developed to meet this objective and simulate fisheries data from a population with distinct habitat preferences. The simulation was used to test several statistical hypotheses regarding best practices for index standardization aimed at accurate estimation of population trends. Effort data from the US pelagic longline fleet was paired with a volume-weighted habitat suitability model for blue marlin (Makaira nigricans) to derive a simulated time series of blue marlin catch and effort from 1986 to 2015 with four different underlying population trends. The simulated CPUE data were provided to stock assessment scientists to determine if the underlying population abundance trend could accurately be detected with different methods of CPUE standardization that did or did not incorporate environmental data. While the analysts’ approach to the data and the modeling structure differed, the underlying population trends were captured, some more successfully than others. In general, the inclusion of environmental and habitat variables aided the standardization process. However, differences in approaches highlight the importance of how explanatory variables are categorized and the criteria for including those variables. A set of lessons learned from this study was developed as recommendations for best practices for CPUE standardization.FCT IF/00253/2014info:eu-repo/semantics/publishedVersio