Characterization of the spawning area of tuna species on the northern Tunisian coasts ; Caracterización del área de puesta de especies de túnidos en las costas del norte de Túnez

Early life stages of tuna species were investigated along the northern coasts of Tunisia in the summer of 2010, from 7 to 14 July. A total of 74 stations, distributed on a regular grid, were sampled. Larvae of five tuna species were identified: the Atlantic bluefin tuna, the bullet tuna, the Atlantic black skipjack, the Atlantic bonito and the albacore tuna. Larval distribution patterns show that Atlantic bluefin tuna and albacore tuna usually spawn in offshore oligotrophic waters and Atlantic black skipjack larvae on the continental shelf. The widespread distribution of bullet tuna larvae, suggests that it spawns on the entire continental shelf and over the shelf break. The results from the quotient analysis carried out to characterize the spawning habitat of each species, show that the input of recent surface Atlantic water (AW) masses play a key role in the spawning strategy of tuna species, particularly in the case of the Atlantic bluefin tuna, whose larvae were mainly caught in the mixed waters resulting from the interaction between recent AW and resident AW, as demonstrated by their preference for salinity values between 36.9 and 37.4. ; Se investigaron las fases larvarias tempranas de especies de túnidos a lo largo de las costas del norte de Túnez, durante el verano de 2010, del 7 al 14 de julio. Se muestrearon un total de 74 estaciones, distribuidas en una malla regular. Se identificaron larvas de cinco especies: el atún rojo, la melva, la bacoreta, el bonito y el atún blanco. Los patrones de distri-bución de larvas muestran que el atún rojo y el atún blanco desovan generalmente en aguas oligotróficas alejadas de la costa. Por contra, la localización relativamente más costera de las larvas de bacoreta indica que esta especie se reproduce sobre la plataforma continental, mientras que la amplia distribución de las larvas de melva sugiere que esta especie desova a lo largo de toda la plataforma y el margen continental. Los resultados del análisis de proporcionalidad, llevado a cabo para caracteri-zar el ...