Effects of diet and temperature on the freshness of European seabass. Combined effects of temperature and dietary lipid level on body composition, growth and freshness profile in European seabass, Dicentrarchus labrax

A mesocosm fish trial was carried out to evaluate the combined effects of rearing temperature and dietary lipid level on the body composition, growth performance and freshness profile of the European seabass (Dicentrarchus labrax). Fish were distributed in 12 tanks (n= 3 tanks/treatment) and kept for 8 weeks at 20 oC and 24 ºC and fed on two diets, with 16% lipid and 20% lipid. At the end of the feeding trial, fish were euthanized at two temperature conditions (0.6 ºC or -0.6 ºC) and kept in ice for 10 days at 4 ºC to evaluate their freshness condition at day 0 and day 10. For freshness evaluation, three methodologies were applied: 1) sensory; 2) physical and 3) culture-dependent and independent microbial analyses. Also, at the end of the trial some fish were frozen and prepared for composition analysis while for estimation of growth performance, initial and final measurements of some specimens were considered. Findings demonstrated that fish reared at 24 ºC presented lower lipid level and higher daily growth index than those fish reared at 20 ºC. On the other hand, condition index did not change among treatments. Additionally, sensory analysis (QIM) and microbiological analysis revealed that fish reared at 24ºC have shown better freshness conditions than those at 20 ºC. Nevertheless, the dietary lipid level did not have any influence in fish freshness condition. So, our data may suggest that the increment of temperature till 24 ºC is beneficial for the rearing conditions of this particular species in aquaculture as well as for its freshness profile. Additionally, the lower euthanasia temperature seems to lead to higher fish freshness than normal killing temperature.