The effect of dietary water content on Dicentrarchus labrax growthparameters and resistance to Vibrio anguillarum infection wasinvestigated using commercial pellets with identical energy contents and differentmoisture levels. The first experiment hypothesis was that moisturizing pelleted ration canhave an impact on Dicentrarchus labrax growth performance by theosmoregulation energy cost reduction. In a second time, the experiment explores the effectof water addition in pellets on the fish resistance to a disease. A specific device wasbuilt to uniformly moisturize dry pellets to different moisture levels, i.e. 8%, 20%, 40%and 60%. After an acclimation period and a 54-day rearing period, the control fish hadgrown from 72.7 ± 17.9 g to133.3 ± 29.4 g. Nosignificant differences were recorded for fish growth parameters. After the growth period,the tagged fish were mixed and challenged by bath exposure to live Vibrioanguillarum in triplicate. After 7 days, mortality was significantly lower inthe group of fish fed with pellets containing 60% water. Adding water toDicentrarchus labrax feed did not affect fish growth parameters butincrease its resistance to a Vibrio anguillarum infection. The moisturizing processcould be used to add specific compounds (such as probiotics or vitamins) to pellets justbefore fish feeding and could have a positive effect on fish rearing.

Sex ratios in farmed European sea bass are highly biasedtowards males (75 to 95%), which is problematic for aquaculture. Inthis mini-review, we re-analyse fisheries literature data aboutsex ratios in wild sea bass from 13 population samples, representing altogether4889 individuals covering the major part of the distribution rangeof the species. We find that as a whole, the sex ratio of wild populationsis biased towards females (59.4% females, p <0.001), but that the sex ratio of the younger fish (<30 cm totallength) is balanced (52.0% females, p = 0.15),while the sex ratio of the older fish is heavily biased towardsfemales (69.5% females, p < 0.01). Possiblecauses of these differences (differential longevity, biased sampling)are discussed. When age-group sex ratios are available (three populationsamples out of 13), significant variation between age groups appears,part of which is most likely of environmental origin. This study showsthat the excess of males in culture is not a characteristic of thespecies, but rather a consequence of the environments used in culture,interacting with a complex system where both environmental and genetic influencesgovern sex determination in sea bass.