SELFDOTT REPORT 2009

SELFDOTT project 2009 Periodic Report

In reproduction, one of the two captive broodstocks --maintained in Spain-- was successfully induced to mature and spawn using the developed controlled-release delivery systems (implants) loaded with GnRHa. The broodstock began spawning on the 29th June 2009, three days after hormonal treatment, and spawned daily for a period of 17 days with a total of 140 million eggs. Daily fecundity ranged between 285,000 eggs to 34,000,000. Fertilization success was almost 100%, as probably only fertilized eggs floated to the surface and were collected. No spawning was observed and no eggs were collected from the other broodstock maintained in Malta and this was perhaps due to too late hormonal treatment and/or the hydrodynamics of the site. Other major results achieved include the study of the age of puberty in captive reared BFT, the development of an efficient broodstock diet for captive BFT, the successful deployment of a broodstock cage light and temperature remote sensing system to monitor and predict induction opportunities and muscle biopsies obtained from a new broodstock in Malta and from individuals spawning in the Levantine Sea for DNA analysis of the population genetics study. Larval rearing husbandry tasks were satisfactorily supplied with Bonito (Sarda sarda) and viable BFT eggs. Several experiments have been implemented using the 3 targeted larval rearing methods: Mesocosm, pseudo green water and clear water. In the best case bonito rearing attempts have been conducted to 80 dph in mesocosm and a small batch initially produced in pseudo green water is still alive (300 dph). In mesocosm swimbladder inflation rates scored between 60 and 78 % while they reached 60 % in pseudo green water and 85% in clear water. In BFT, the rearing time lasted 60 dph in mesocosm, 73 dph in pseudo green water and 20 dph in clear water. In mesocosm swimbladder inflation rates was 50 %, scored 58 % in pseudo green water but ranged between 1.2 and 5 % in clear water. Light intensity, lighting regime, hydrodynamics, surface cleaning, microalgae addition, feed sequence and nutritional quality have been identified as the main factors to be fine tuned mainly during the larval rearing stage. In order to obtain molecular tools for the spatial and temporal localization of the corresponding transcripts, genes of interest were partially cloned. The early development of BFT posterior lateral line has been examined. Ontogeny of digestive tract in Bonito and BFT was rather extensively described. Regarding the immune system ontogeny, a preliminary approach has been conducted. Other studies including the evaluation of the microbiotal diversity of the digestive tract and the bacterial characterization in larvae have been carried out. For Nutrition and feeding studies, Young Bluefin Tuna (YBFT) were used to start the artificial feeding trials. First weaning trials with artificial food was successfully achieved. A trial to compare two diets: raw fish and artificial food has been started. The stomach analyses of captured dead YBFT showed that fish are the main prey (37% in weight), followed by cephalopods (11%) and crustaceans (5%). The main prey species is the round sardinella (Sardinella sp). These results contrast with the ones obtained last year where cephalopods were the main prey, so YBFT can be considered a generalist feeder. From the body composition analyses it seems that YBFTs have different nutritional requirement from most other Mediterranean aquaculture species: high protein and low fat content with significantly higher values of EPA+DHA for YBFTs and higher amino acid concentrations. In the dissemination of the results, nine Conference presentations have been held and close to 100 press releases have been published mainly in Spain and France. Furthermore the SELFDOTT project web site is now on-line at www.selfdott.org.

Commission of the European Communities, specific RTD programme of Framework Programme 7,“Theme 2-Food, Agriculture, Fisheries and Biotechnology, SELFDOTT project: “From capture based to SELF-sustained aquaculture and Domestication Of bluefin tuna, Thunnus Thynnus”. Grant Agreement number: 212797