Abstract
SUMMARY: Following previous observations, this study was undertaken to determine the level of salt required in the diet of gilthead sea bream (Sparus aurata L.) juveniles in order to enhance growth performances and survival when rearing in inland brackish water with a salinity of 2.9‰ TDS (Total Dissolved Salts). The juveniles were reared for 10 weeks in twelve rearing tanks, each stocked with 65 fish. Four different test diets were prepared: a control diet without added salt, and three diets with 12%, 14% and 16% added salt. Fish were fed by hand ad libitum three times daily. All diets were accepted equally well. The highest growth rate (p<0.05) was achieved in fish fed the 12% diet followed by the 14% diet, the control diet, and finally the 16% diet. The 12% diet produced the best specific growth rate, feed conversion ratio and protein efficiency ratio. The highest survival was achieved in fish fed the 12% diet (88%) and the lowest in fish fed the 16% diet (80%) and the control diet (80%). This study demonstrates that growth performance and survival in gilthead sea bream reared in water of low salinity can be significantly improved by adding 12% salt to their diet.
Highlights
Gilthead sea bream is a euryhaline teleost capable of living in environments with salinities ranging from 2‰ to 60‰
All experimental diets were accepted by the fish well, the highest growth rate (p
Table 2. – Growth performance of gilthead sea bream (S. aurata L.) juveniles fed different salt-added diets for 10 weeks
Summary
Gilthead sea bream is a euryhaline teleost capable of living in environments with salinities ranging from 2‰ to 60‰. Its natural habitat stretches from the Mediterranean and Black Sea to the eastern Atlantic Ocean from Senegal to the United Kingdom. It is commonly found in shallow lagoons along the coast, but migrates into deeper water to spawn after late autumn. Fish in low-saline water show a passive outward flux of ions such as Na+ and Cl- to the water via the gills, faeces and renal system, which. The major osmoregulatory organ in fish, undergo large morphological changes at low water salinities. Euryhaline fish in different environmental salinities induce activation of their ion transport mechanism, usually accompanied by changes in oxygen consumption, causing variations in the energy demands for osmoregulation
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