The study was conducted to assess trace metal contents, biochemical composition and growth performance of axillary seabream (Pagellus acarne Risso, 1827) cultured in a copper alloy mesh cage. A total of 400 axillary seabream (initial mean weight: 176.0±14.0 g), a new candidate species for the Mediterranean aquaculture, were stocked into a high-density polyethylene frame gravity cage and fed a commercial seabream diet for a period of 6 months. At the end of the feeding trial, fish reached a final weight of 264.8±16.8 g with a weight increase of 88.8 g and a feed conversion rate of 2.51. Overall, relative growth rate, specific growth rate and feed conversion ratio were satisfactory and comparable to the pelagic fishes such as gilthead seabream or European seabass, which are presently the main fish species for the Mediterranean aquaculture industry. Trace elements in fish grown in copper alloy net cages over a 6-month period showed satisfactory results, as the metal concentrations in fish tissues such as liver, skin, muscle and gills were below the reported upper limits for human consumption, indicating that copper alloy net is an acceptable and safe material for finfish cage aquaculture. Furthermore, from the growth performance data obtained in the present study, it can be concluded that axillary seabream showed potential for cage farming, and thus is a promising new candidate for the Mediterranean aquaculture industry.

Abstract:In the present study, the effects of different dietary protein levels on salema porgy, Sarpa salpa (Linnaeus, 1758) juveniles were investigated. Six iso-caloric (20 kJ/g diet) diets with increasing protein levels (30, 37, 40, 47, 50, and 57%) were formulated. Each test diet was randomly fed to triplicate groups of 13 juvenile fish (initial mean weight 19.28±0.13 g) to satiety over 90 days. Growth performance and feed utilization were best with low dietary protein levels of 30 and 37%, but decreased with diets containing protein levels over 40%. Ammonia nitrogen excretion showed an increasing trend as dietary protein levels gradually increased, whereas retention rates of ammonia nitrogen per intake were highest in the low protein groups of 30 or 37%. The analyses of specific growth rate by broken-line regression indicated that the optimal dietary level of protein for salema porgy juvenile were 33.6% under the conditions applied in this study. As a result, S. salpa demonstrated better growth with low protein diets, showing that this marine fish could be a promising candidate for a sustainable and environment friendly aquaculture industry.

The effects of different dietary protein levels on growth performance and health status of TwobandBream Diplodus vulgaris juveniles were investigated. Three test diets that had increasing protein levels (30, 36, and 42%) and used fish meal as the protein source were formulated. Each of the test diets was fed in triplicate groups of 28 juvenile fish (initial weight, 23.65 ± 0.34 [mean ± SD]) to satiety for a period of 80 d. Growth performance and feed utilization were best in the group fed the diet with a protein level of 36%. Ammonia nitrogen excretion showed an increasing trend as dietary protein levels increased, and retention rates of ammonia nitrogen per intake were highest in fish fed the 42% protein diet. Whole‐body proximate composition and hematological variables were not significantly affected by protein level in the diets. However, serum glucose, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) values were significantly affected by dietary protein level and showed an increasing trend as the dietary protein level in the diets increased. As a result, an improved health status of Twoband Bream was observed in the fish fed a 36% protein level.