Deslocamentos horizontais e verticais de pequena escala realizados pela albacora laje Thunnus albacares no Arquipélago São Pedro e São Paulo

Abstract

The yellowfin tuna, Thunnus albacares, is an epipelagic oceanic species very captured in the tropical Atlantic Ocean, being an important fishing resource in the region of Sao Pedro and Sao Paulo Archipelago (ASPSP). Few researches have studied so far the behavior of this species of tuna in this area, which is probably affected for several biotic and abiotic factors of the ocean. For this reason, this research has tried to found the behavior of yellowfin tuna through the use of marked satellite experiments in other to obtain information on small-scale circadian displacements and their preferential thermophymetric habitat in the ASPSP. A total of eigth samples of yellowfin tuna were attached with PAT attached programmed to operate for periods of 15 to 120 days, registering the water temperature, the depth and luminosity of the environment for the purpose of estimation displacement. All the tags were released before the expected time with the marked time raging from one to thirteen days and marked released points occurred between 0,77 and 79,05 MN of ASPSP revealing that this specie stay for few days in the archipelogo area, which is an important trophic region due to high concentration of marine life, specially flying fish (Cypselurus cyanopterus). With the achieved results it was possible to observe a clear preference of the species for the homogenous layers (0-50,0 m) whose average temperature recorded was 27,2°C. Data collection of all tagged fish showed 83.5% of total experiment time in the homogeneous layer, 46.3% at night (17:00 - 5:00 h) and 37.2% at daytime. The thermocline strip was also visited by the labeled specimens, with 12.9% of the marking time and temperatures between 13.9 ° C and 20.3 ° C. The deepest dive was done at 488,0 m with temperature of 7,3°C,however, was noticed that this is not a common behavior for these species, suggesting some hypotheses like the search for food, scape from predators or even a bathymetric exploration by the species. The results obtained in this study indicate the preference of the species for surface and warm waters of the homogeneous layer in the surroundings of the ASPSP, although sporadic dips to the interior and below the thermocline are realised. It was also possible to observe that the species remains in the region in trophic activity for some days, although new experiments are necessary to better understand this dynamics of horizontal displacements carried out by the species in the region.