Biometric relationships and fattening rate of bluefin tuna Thunnus Thynnus Thynnus l. 1758 in a Tunisian fish farm

Abstract

An analysis of data from a Tunisian farm during the months of June to November of the year 2008 is presented. These data were broken down into two sets the first concern sampled fish while towing them to farm (wild set),  the second set concern sampled specimen at the end of fattening process (fattening set). The wild group comprised specimens ranging from 90 to 276 cm fork length, and the fattened group included specimens from 105 to 310 сm. Juvenile proportion (Lf<130 сm) in fattened specimen (15.7%) was considerably smaller compared to the proportion in wild specimens (61,8%). The distribution of individual weights of slaughtered BFT shows the prevalence 31-50 kg specimen class (60.4%). The L-W relationships were determined for each of these sets. This relationship was based on 1727 specimens sampled during the fattening period. A preliminary Fork length-Head size and Fork length Maximum height relationships were estimated for fattened specimens. Those relationships were based respectively on 1547and 684 specimens. The RWT of fattened specimens meant a higher weight than in wild BFT for the same size. Fish size between 90 and 160 cm Fl presented a higher fattening rate (42%) than larger fish (>160 cm Fl) (32%).