Distribution of tuna larvae in Tunisian east coasts and its environmental scenario

Early life stages of tuna species were investigated along the Tunisian east coast during the summer of 2008 by means of a larval survey conducted on board the R/V HANNIBAL. In this study we define the spawning grounds of tuna fishes in Tunisian waters and relate the tuna larvae spatial distribution to the hydrographic features and other environmental parameters. A total of 282 larvae of Atlantic bluefin tuna (Thunnus thynnus, Linnaeus, 1758), 902 of bullet tuna (Auxis rochei, Risso, 1810) and 19 of little tuna (Euthynnus alletteratus, Raf, 1810), were identified. High larval concentrations of bluefin tuna were located offshore (mean = 200 ± 18 m), at sea surface temperatures ranging between 23.7 to 25.3°C, whereas the highest concentrations of bullet and little tuna were located in shallower waters (mean = 135 ± 75 m), at sea surface temperature ranging between 25.1 to 25.9°C. According to their preference for waters with surface salinities ranging between 37.1 and 37.8, spawning of these species seems to occur mainly in mixed waters. Stations where tuna larvae were collected showed oxygen concentrations between 6.55 and 6.85 mg l-1, as well as low turbidity and chlorophyll a values, from 0.2 to 0.5 NTU a d less than 1 mg m-3, respectively. These three environmental factors were weakly correlated with tuna larvae abundancePublicado