PRELIMINARY RESULTS OF CAPTURE, TRANSPORT AND ADAPTATION TO CAPTIVITY OF JUVENILES OF BLUEFIN TUNA THUNNUS THYNNUS

Domesticating a fish is a slow and complex process, including the knowledge about its behaviour and habitat, its general needs, its reproductive biology, its nutritional requirements, the larvae and juveniles physiology, the development of the techniques of massive culture as well as the knowledge about its susceptibility to diseases in culture conditions. To obtain this information it is necessary to control the different phases of the life cycle in a place, which allows an easy access, not only to the fish but also to its environment. In order to do that, it is important to adapt them to land-based facilities, which allows carrying out studies on aspects of its physiology, which would be very difficult or practically impossible, in the wild or in open sea facilities. In this way and waiting for the development of techniques that allows to get viable spawns and juvenile production of bluefin tuna (BFT) in captivity, we might advance in the knowledge about the handling of BFT juveniles through its capture from the wild. During November 2006 BFT juveniles were captured alive on the shore of Murcia (SE Spain) using a plastic-baited barb less hook, and were placed in a cylindrical plastic tank (1.45-1.65m Ø, 1.20m height, with 1200 litters of sea water) to transport from fisheries areas to land based facilities. The water temperature was 19-20ºC. A van with a similar plastic tank was used to transport the fish overland. A pure oxygen supply and circular water current were arranged into all the tanks. All of these devices were placed under a double PVC bottom holed to avoid any kind of obstacles against the normal swimming of tunas. The land-based tank was a cylindrical 20m3 fibber glass tank (4m Ø, 2m height). From a total of 57 captured individuals weighing 1577g ± 192 and with a 43cm ± 1.5 fork length (mean ± SD) only 12 were transported alive from the fishing areas to the land based facilities. All of individuals that swam regularly in the transport tank on the boat, withstood the overland transport and arrived alive to the IEO-Mazarrón facilities. In the land-based tank, BFT swam regularly in circles without touching the tank walls. No fish survived more than 72 hours. The dead fish showed dark areas in their surface and injuries in the skin. The accidental friction with the tank walls and the handling with the rubber net when fish were transfer from the boat to the van and from the van to the land-based tank could be the reason of the final mortality. Thus, it would be necessary to design a system that minimizes this friction. This study has been carried out in the frame of the project ADAR (Advances in Domestication of Bluefin tuna Thunnus thynnus) funded by IEO, Regional Government of Murcia and Ricardo Fuentes Group.