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Rodriguez-Marin E.,Spanish Institute of Oceanography | Ortiz M.,International Commission for the Conservation of Atlantic | De Urbina J.M.O.,CO Malaga | Quelle P.,Spanish Institute of Oceanography | And 15 more authors.
PLoS ONE | Year: 2015

The compiled data for this study represents the first Atlantic and Mediterranean-wide effort to pool all available biometric data for Atlantic bluefin tuna (Thunnus thynnus) with the collaboration of many countries and scientific groups. Biometric relationships were based on an extensive sampling (over 140,000 fish sampled), covering most of the fishing areas for this species in the North Atlantic Ocean and Mediterranean Sea. Sensitivity analyses were carried out to evaluate the representativeness of sampling and explore the most adequate procedure to fit the weight-length relationship (WLR). The selected model for the WLRs by stock included standardized data series (common measurement types) weighted by the inverse variability. There was little difference between annual stock-specific round weight-straight fork length relationships, with an overall difference of 6% in weight. The predicted weight by month was estimated as an additional component in the exponent of the weight-length function. The analyses of monthly variations of fish condition by stock, maturity state and geographic area reflect annual cycles of spawning and feeding behavior. We update and improve upon the biometric relationships for bluefin currently used by the International Commission for the Conservation of Atlantic Tunas, by incorporating substantially larger datasets than ever previously compiled, providing complete documentation of sources and employing robust statistical fitting. WLRs and other tuna from the International Commission for the Conservation of Atlantic Tunas. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Saber S.,University of Malaga | Macias D.,CO Malaga | de Urbina J.O.,CO Malaga | Kjesbu O.S.,Norwegian Institute of Marine Research | Kjesbu O.S.,University of Oslo
Fisheries Research | Year: 2016

A range of methods can be applied to estimate the batch fecundity of species with an indeterminate reproductive strategy. The traditional Hydrated Oocyte (HO) method based on direct counts of hydrated oocytes is the easiest and most accurate method but the main problem with this method is the shortage of hydrated ovaries in sampled fish such as tuna species. Batch fecundity estimates of albacore Thunnus alalunga resulting from counts of migratory nucleus (MG) oocytes using the application of the Weibel and Gomez (W&G), Physical Disector (PD), Oocyte Packing Density (OPD), and HO methods were compared using the last method as "control". Postovulatory follicles (POFs) were also counted using the PD method. Correction factors due to shrinkage were considered in the application of the different methods. Our results showed the highest batch fecundity estimates were obtained with the design-based PD method. The outputs from the assumption-based W&G and the theoretical OPD methods were closest to the HO method. Annotations of POFs instead of MG oocytes gave markedly lower values. The new OPD method was used to estimate batch and relative fecundity on a larger sample of fish (selected according to their length). The relationships between batch and relative fecundity estimates of albacore and the associated biological metrics (length, body weight and ovary weight) were investigated. Batch fecundity estimates ranged from 0.42 to 2.16 million oocytes with a mean relative batch fecundity of 136 oocytes per gram of body weight. The batch fecundity was shown to increase with fish size (length and weight) and gonad weight, while relative batch fecundity (g-1) was related only to gonad weight. © 2015 Elsevier B.V.

Garcia-Ruiz C.,CO Malaga | Lloris D.,CSIC - Institute of Marine Sciences | Rueda J.L.,CO Malaga | Garcia-Martinez M.C.,CO Malaga | Gil de Sola L.,CO Malaga
Journal of Natural History | Year: 2015

This study describes the four main demersal fish assemblages identified along the continental shelf and slope (30–800 m depth) of the northern Alboran Sea (western Mediterranean), based on the analysis of the MEDITS (International bottom trawl survey in the Mediterranean) 12-year data series. We collected 186 fish species belonging to three classes, 24 orders and 69 families. Taxonomically, the order Perciformes was the most diverse, represented by 18 families and 58 species. Each assemblage had particular characteristics of abundance, biomass, mean fish weight and species richness. The geographical differences associated with the distribution of some species occurred within shelf assemblages. The middle slope was characterised by the highest similarity between samples, probably due to its lower environmental variability compared to that of the other assemblages. © 2015, Taylor & Francis.

Vargas-Yanez M.,CO Malaga | Zunino P.,CO Malaga | Schroeder K.,CNR Marine Science Institute | Lopez-Jurado J.L.,C.O. Baleares | And 6 more authors.
Journal of Marine Systems | Year: 2012

The Western Intermediate Water (WIW) is probably the less studied water mass in the Western Mediterranean (WMED). It is clearly identifiable as a temperature minimum above the Levantine Intermediate Water (LIW). The WIW circulation from the northern part of the WMED to the south and through the Balearic Channels is well known, but no specific experiments have been devoted to the study of the formation process of this water mass. It is usually accepted, in a vague sense, that WIW is formed in the northern sector of the WMED, in areas surrounding the Gulf of Lions, the Ligurian Sea and the Catalan Sea, being advected towards the Balearic Channels as part of the northern current. The present work shows hydrographic data obtained in late winter in 2010 after severe storms in the WMED. These data show intermediate convective mixing along the whole continental shelf of the Iberian Peninsula, as far to the south as Cape Palos. The data analysed show that, under severe winter conditions, the formation area of WIW is larger than previously thought and the salinity and temperature ranges for this water mass are also wider than those traditionally accepted in the literature. © 2012 Elsevier B.V.

Baez J.C.,CO Malaga | Baez J.C.,University of Malaga | Ortiz de Urbina J.M.,CO Malaga | Real R.,University of Malaga | Macias D.,CO Malaga
Journal of Applied Ichthyology | Year: 2011

The aim of this study was to look into possible relationships between climate and the inter-annual variability of albacore (Thunnus alalunga) catch rates by age class observed during a recreational fishery tournament at the spawning grounds of S'Estanyol (Balearic Islands, Spain) in the years 2004-2009. The mean capture per unit effort (CPUE) was significantly higher when the mean of the North Atlantic Oscillation (NAO) experienced by the albacore in winter and spring of its life history (NAO life) was negative than when the NAO life was positive. A statistically significant negative relationship was obtained between NAO life and the probability of a CPUE value for an age class and year being higher than the average CPUE for all the cohorts in that age class. The results suggest that local abundance of albacore in a spawning grounds could be related to environmental factors dependent on the NAO and that there may be a cohort-age effect. It is hypothesized that factors dependent on the NAO, such as the abundance variation of small pelagic fishes as a response to the NAO variability, could have a cumulative effect over the good biological condition (fitness) of a long-living fish predator such as the albacore. © 2011 Blackwell Verlag, Berlin.

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