Description of the ICCAT length at age data base for bluefin tuna from the eastern Atlantic, including the Mediterranean Sea

This study aims to describe the current length at age database available for Eastern Atlantic bluefin tuna management area. A total of 8 500 spines and 5 000 otoliths were read from specimens caught from 1984 to 2017 in both the Atlantic Ocean and Mediterranean Sea. Obtaining ALKs for this species is difficult, as it has a wide length range and spatial distribution, and sampling is costly. Unfortunately, there are practically no contributions to this database from the East Atlantic and Mediterranean Sea countries, and only thanks to the initiative of the GBYP has it been possible to increase the number of samples in the ICCAT database in the last 10 years. As a result, the current ICCAT length at age database has incomplete spatial, temporal and size range coverage. However, it may be suitable as conditional age-at-length data for the Stock Synthesis model

Spanish albacore (Thunnus alalunga) surface fishery in the Northeastern Atlantic, summary description in 2018.

Main features of the Spanish albacore (Thunnus alalunga) surface fishery in 2018 were summarized. Fishing activity took place during summer from June to August operating in offshore waters of the northeast Atlantic and in the Bay of Biscay. Albacore was targeted by troll fleet from June to August, mostly in off shore waters of northeast Atlantic and the baitboat in the Bay of Biscay. In 2018, the catch of the baitboat fleet increased 38% while troll fleet increased 15% compared to catch in year 2017. Size composition of catches taken by baitboats and troll fleets in 2018, showed a high proportion of age 2 group, followed by equivalent proportion of age 1 and age 3 groups albacore. Monthly spatial distribution of nominal catch rates were presented for both fleets

Standardized age - Length key for east Atlantic and Mediterranean bluefin tuna based on otoliths readings.

This paper presents an age-length key (ALK) based on age estimates from otoliths following a recent standardized reading criterion. Sampling of Atlantic bluefin tuna (Thunnus thynnus) otoliths comes from the “Biological and genetic sampling and analysis" (GBYP) project and was complemented with some samples from the Spanish institute of Oceanography. Using 2010 to 2012 data improves length range and monthly sampling coverage. Variability in length at age from ALK seems acceptable and although it was developed from data pooled over three years, the bias is likely to be small. Final age was adjusted to account for the date of capture and the timing of bands formation throughout the year. Monthly formation of edge type, translucent or opaque, was inconclusive and did not allow establishing an annual formation pattern. The confidence interval of the von Bertalanffy growth model curve fitted to ALK data included currently adopted growth function for eastern bluefin stock and western stock function up to age 8. From age 9, this last western function predicts slightly older ages than the present ALK growth model.Postprint0,000

Age-length keys availability for Atlantic bluefin tuna captured in the eastern management area

This paper analyzes the available direct ageing information in the last decade from Atlantic bluefin tuna caught in the eastern management area. To investigate differences among ALKs, a standard Von Bertalanffy growth function (VB) was fit to length at age data for each stratum. A deficient convergence of VB fitting to the asymptotic length due to the scarcity of old specimens was found for all available ALKs. After these analyses some records were identified as outliers (reading methodological issues) and removed from the data base.En prensa0,000

A review of Mediterranean albacore (Thunnus alalunga) biology and growth studies

Growth parameters are used to estimate catch-at-age data which is required as an input to many stock assessment models. In the case of Mediterranean albacore stock no assessment has ever done (ICCAT, 2009). This study presents growth information based on spine section interpretation of annual time marks. A preliminary age-length key is presented for males, females and two sexes combined, based on 249 albacore (Thunnus alalunga, Bonn.1788) spine samples caught around the Balearic Islands and Western Mediterranean sea between June and November from 2004 thru 2006. The albacore length ranged from 52 cm to 94 cm for females and from 53 cm to 96 cm for males. Available length-weight data for 138 males and 162 females was analysed separately. New estimates presented in this study were compared with assumed biological length-weight relationship for Mediterranean albacore stock. As well, mean length by age estimates derived from the age-length-key obtained by reading fin ray section were compared with other studies that used hard parts to age Mediterranean albacore.Des paramètres de croissance sont utilisés pour estimer les données de prise par âge requis en tant que valeur d’entrée pour de nombreux modèles d’évaluation des stocks. Dans le cas du stock de germon de la Méditerranée, aucune évaluation n’a jamais été réalisée (ICCAT 2009). Cette étude présente des informations relatives à la croissance en se fondant sur l’interprétation des sections des épines des marques annuelles. Une clé âge-taille provisoire est présentée pour les mâles, les femelles ainsi que pour les deux sexes combinés, reposant sur 249 échantillonnages d’épines de germons (Thunnus alalunga, Bonn, 1788) capturés dans les environs des îles Baléares et de la Méditerranée occidentale entre le mois de juin et de novembre 2004 jusqu’en 2006. La taille du germon oscillait entre 52 et 94 cm dans le cas des femelles et entre 53 et 96 cm dans le cas des mâles. Les données disponibles de longueur-poids des 138 mâles et 162 femelles ont été analysées séparément. De nouvelles estimations présentées dans cette étude ont été comparées à la relation biologique postulée longueur-poids du stock de germon de la Méditerranée. De plus, les estimations moyennes de la longueur par âge (dérivées de la clé âge-longueur) obtenues sur la base de la lecture de la section du rayon de la nageoire ont été comparées avec d’autres études qui ont recours à des pièces dures pour déterminer l’âge du germon de la Méditerranée.Se utilizan los parámetros de crecimiento para estimar los datos de captura por edad que se requieren como entradas para muchos modelos de evaluación de stock. En el caso del stock de atún blanco del Mediterráneo, no se ha realizado nunca una evaluación (ICCAT, 2009). Este estudio presenta información sobre crecimiento basada en la interpretación de marcas anuales de secciones de espinas. Se presenta una clave edad-longitud provisional para los machos, las hembras y ambos sexos combinados basada en 249 muestras de espinas de atún blanco (Thunnus alalunga, Bonn. 1788) capturado alrededor de las islas Baleares y en el Mediterráneo occidental entre junio y noviembre de 2004 hasta 2006, inclusive. La longitud del atún blanco oscilaba entre 52 cm y 94 cm para las hembras y entre 53 cm y 96 cm para los machos. Los datos disponibles de longitud-peso para 138 machos y 162 hembras fueron analizados por separado. Las nuevas estimaciones presentadas en este estudio se compararon con la relación biológica longitud-peso asumida para el stock de atún blanco del Mediterráneo. Asimismo, las estimaciones de longitud media por edad derivadas de la clave edad-longitud y obtenidas mediante la lectura de secciones de rayos de aleta, se comparan con otros estudios que utilizaron partes duras para determinar la edad del atún blanco del Mediterráneo

Variación interanual en la presencia de cetáceos en la división 3L del área de regulación de la Northwest Atlantic Fisheries Organization (NAFO, Flemish pass)

Peer reviewe

Updated comparison of age estimates from paired calcified structures from Atlantic bluefin tuna

In this paper we present an updated comparison of age estimates from otoliths and spines from the same specimen, with the intention to analyze whether it is possible to use both structures in obtaining age-length keys for this species. The agreement between otolith and spine age estimates was good for bluefin tuna younger than 14 years old with less than one year difference. Tests of symmetry showed the asymmetrical distribution of ages. However no significant differences were found between the growth parameters estimated from both paired hard parts. It is suggested using both structures readings for constructing agelength keys for bluefin tuna younger than 14 years.En prensa0,000