Search

Abstract: Populations of a rheophilic cyprinid Barbus barbus have declined in last decades, which created a need of conservation aquaculture. Production of stocking material in controlled conditions calls for optimization of the two major factors, temperature and diet. Condition, growth and food conversion ratio in fish fed a formulated diet Aller Futura were compared with those on natural food—frozen Chironomidae larvae at 17, 21 and 25°C. Groups of 60 early juveniles (0.6–3.7g) were reared in each of 18 aquaria in which six experimental groups were run in triplicate. Daily food ratios were adjusted according to fish biomass, differences in hydration between the two diets and rearing temperature. No mortality occurred during the experiment. Condition coefficient K was significantly higher in fish fed Aller Futura compared to those fed Chironomidae irrespective of temperature tested; body deformities were not recorded. Relative growth rate at the same temperature was always higher in fish on the formulated diet than in those fed Chironomidae, and food conversion ratio was always suppressed, both suggesting an efficient utilization of Aller Futura for growth in B. barbus early juveniles. On both diets the coefficient K was depressed at 21°C. Relative growth rate (RGR) was accelerated with temperature according the Krogh’s “normal curve” within the range 21–25°C, while at lower temperatures (17–21°C) the observed values of temperature coefficient Q 10 were much higher than the theoretical Q 10 values based on Krogh’s “normal curve”. Food conversion ratios (FCR) were reduced on both diets at 21 and 25°C. Theoretical optimum temperatures for food conversion were 22.0 and 23.6°C. Summing up, responses of three independent indices: condition, growth and food utilization locate the optimum temperature for B. barbus between 21 and 25°C. No evidence was found that the effect of temperature on these indices was substantially modified by the diet. [Copyright &y& Elsevier]

Juvenile Haliotis rufescens were reared in the laboratory in order to investigate the extent to which fresh kelp and formulated feeds with 250 g kg−1 (25P) and 380 g kg−1 protein content (38P) affected their growth rate, gut residence time (GRT), food consumption ( C), food conversion ratio (FCR) and digestibility. Abalone from 38P attained the highest growth rate (70.5 ± 4.2 μm day−1; 98.3 ± 6.95 μg day−1), followed by 25P (47.9 ± 2.79 μm day−1; 67.4 ± 2.82 μg day−1) and kelp (23.6 ± 3.36 μm day−1; 28.2 ± 4.11 μg day−1). No significant differences were observed in consumption rate among treatments (0.61–0.68% body weight per day), yet kelp-fed abalone exhibited higher FCR (2.44), protein efficiency ratio (4.42), and apparent digestibility of dry matter (69.5%), protein (69.8%) and gross energy (79.2%) than 38P organisms (59.8, 62.4 and 62.2%, respectively). They also showed longer GRT (23.1 ± 0.93 h). This study demonstrated that formulated diets with 250 g kg−1 and 380 g kg−1 protein inclusion can sustain higher growth rates of juvenile H. rufescens than fresh algae. These differences seem to be due to the amount of dietary protein. Kelp meal appears to improve the consumption and digestibility of balanced diets, and its inclusion in formulated diets is recommended. [ABSTRACT FROM AUTHOR]

The effects of different daily feeding rates on the specific growth rate and food conversion ratio of Siberian sturgeon (Acipenser baeri) were investigated in order to determine the optimum daily feeding rate for fish with an initial mean weight of 1736 ± 37 g. To this end, a Latin Square experimental set-up was designed consisting of four groups of 25 fish fed a rainbow trout diet at four different daily feeding rates (0.75, 1.00, 1.25 and 1.50% body weight/day) for four 2-week periods. Water temperature varied between 19 and 22 °C throughout the experiment. Mean specific growth rate and food conversion ratio values were found to be significantly different (P < 0.05) between the four treatments. The means of specific growth rate and food conversion ratio for fish fed at 0.75%, 1.00%, 1.25% and 1.50% body weight/day were computed as 0.47, 0.88, 0.89 and 0.64% day-1 and 1.71, 1.25, 1.40 and 2.43, respectively. At 19-22 °C the optimum daily feeding rate for Siberian sturgeon of 1736 g was determined to be 1.00% body weight/day. [ABSTRACT FROM AUTHOR]