Evaluation of Atlantic bluefin tuna reproductive potential in the western Mediterranean Sea |
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| Institution: | 1. Faculty of Marine Sciences & ECIMAT Marine Station, University of Vigo, Campus Universitario de Vigo, 36310 Vigo, Spain;2. Grupo de Acuicultura Marina, Centro Oceanográfico de Vigo, Instituto Español de Oceanografía Subida a Radio Faro, 50. 36390 Vigo, Spain;3. Instituto Nacional de Investigación y Desarrollo Pesquero Paseo Victoria Ocampo N° 1. B7602HSA, Mar del Plata, Argentina;1. Instituto Español de Oceanografía, Centre Oceanogràfic de les Balears, Moll de Ponent s/n, 07015 Palma de Mallorca, Spain;2. Instituto Español de Oceanografía, Centro Oceanográfico de Murcia, 30860 Puerto de Mazarrón, Murcia, Spain;3. Department of Biology, University of Bergen, 5020 Bergen, Norway;4. Institute of Marine Research, 5817 Bergen, Norway |
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| Abstract: | Ovarian tissue samples of Atlantic bluefin tuna (ABFT) spawners (n = 49) caught by purse seine in the Balearic Sea (western Mediterranean) were used to assess the stock reproductive characteristics. The frequency of spawning females estimated by the postovulatory follicle method was 84% and the spawning periodicity 1.2 days. Using an unbiased stereological method, the realized batch fecundity was estimated from counts of postovulatory follicles (POFs), whereas the batch fecundity of the subsequent spawn was estimated by quantification of the number of follicles containing oocytes at maturation stage (OMFs). The number of POFs was used as a reliable proxy of the realized batch fecundity, as it represents the actual number of eggs released in the last spawning event. The average relative realized batch fecundity was estimated to be approximately 48 eggs g− 1 of total body mass. While the absolute batch fecundity was isometrically related to the fork length, the relative batch fecundity was not dependent on fish size, which leads to the assumption that all length classes contribute proportionally to their size, towards the total number of eggs spawned by the broodstock. Size-related variations in the sex ratio were observed in the study area and in other Mediterranean locations; females were more abundant in mid-size classes while males predominated in large-size classes. |
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