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An experimental study was undertaken to assess the impact of substrate and periphyton on the growth, survival and feed utilization of Penaeus vannamei. This study was conducted in cement tanks with bamboo as substrate. The average submersion depth of the substrates was maintained at 85.16 ± 0.26 cm in the treatment tanks. There was significant difference (P value < 0.05) observed in the values of Chlorophyll a (3.12 ± 0.32 µg/cm2 minimum and 16.29 ± 1.15 µg/cm2 maximum values), dry weight (2.49 ± 1.46 mg/cm2), ash (0.78 ± 0.46 mg/cm2), ash free dry weight (1.71 ± 1.0 mg/cm2) and autotrophic index (146 ± 18) in terms of submersion time but there was no significance observed in terms of substrate depth. The bio growth parameters (Average Body Weight - 15.4 ± 4.9 g, Average Daily Growth - 0.165 ± 0.01 g, Specific Growth Rate - 7.67 ± 0.03, Protein Efficiency Ratio - 3.12 ± 0.15 and Food Conversion Ratio - 0.92 ± 0.00018) were also observed to be high in treatments with the substrate. Feed usage in the treatment tank was found to be reduced by 19% compared to the control tank. The Periphyton community recorded on the treatment tanks with split bamboo poles as substrate comprised of 4 groups (Bacillariophyceae, Chlorophyceae, Cyanophyceae and Euglenophyceae). The results on the depth-wise analysis of microbial load on the split bamboo substrate have shown a significant difference between 10 cm and 40 cm depth and 10 cm and 70 cm depth of the substrate (P<0.05), whereas, there was no significance observed between 40 cm and 70 cm depth of the substrate in the microbial load. Under the low saline condition, substrate-based vannamei farming has shown better performance compared to the tanks without substrate. [ABSTRACT FROM AUTHOR]

An ontogenetic dietary shift is crucial for the survival and growth of piscivorous largemouth bass (LB). However, there is much to learn about the predator-prey interaction during the switching process. We carried out a series of indoor experiments to examine the predation capacity, predation preference, and growth performance of exotic juvenile LB feeding on candidate prey species in the Pearl River Delta. The widely distributed oriental river prawn (Macrobranchium nipponense), barcheek goby (Ctenogobius giurinus), western mosquitofish (Gambusia affinis), silver carp (Hypophthalmichthys molitrix), and mud carp (Cirrhinus molitorella), with relatively similar total lengths, were selected as potential prey based on their availability and habitat use. Our results show that predation capacity and preference varied quantitatively and qualitatively among prey species. The number of oriental river prawns killed was significantly less than that of fish species, comparing the 1st hour with the 24th hour (p < 0.01). The feeding rhythm of LB varied significantly from crayfish to fish. Numerically, Jacobs’ selection index reinforced LB’s special preference for predating G. affinis. Although there were obvious variations in predation capacity and feed selection, no statistically significant growth differences were detected among LB groups feeding on live M. nipponense, G. affinis, H. molitrix, and C. molitorella (p < 0.05). These findings suggest that the successful ontogenetic dietary shift of juvenile LB may depend on the availability and vulnerability of local fish species. Further study on the reproductive phenology of potential fish prey may help to predict LB’s establishment.

Aquaculture's success highly depends on a controlled rapid growth of organisms with minimal costs associated. Growth and welfare of reared organisms are affected by physical, chemical, and biological parameters. Following factors can be highlighted as crucial: density, pH, salinity, temperature, dissolved oxygen (DO), and nutrients (nitrogen, phosphorus, etc.). Relationship between fish density and oxygen's optimum levels is essential for designing the performance of each species. Furthermore, it is also necessary to study fish stress factors and physiological responses. Two rearing experiments with gilthead seabream (Sparus aurata) were performed, in order to test different densities (5, 10 and 20 kg/m3) for 9 weeks (271 ± 1.9 g) and to test different levels of oxygen (40%–60%, 60%–80%, and 80%–100%) for 6 weeks (316.3 ± 1.73 g). In both experiments, physiology and growth parameters were analysed, as well as water quality. This study showed that no relation was observed between density and fish physiology, but there structural (gill lesions) and physiological changes (haematocrit) were observed for seabream reared at low levels of DO. [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]

An ontogenetic dietary shift is crucial for the survival and growth of piscivorous largemouth bass (LB). However, there is much to learn about the predator-prey interaction during the switching process. We carried out a series of indoor experiments to examine the predation capacity, predation preference, and growth performance of exotic juvenile LB feeding on candidate prey species in the Pearl River Delta. The widely distributed oriental river prawn (Macrobranchium nipponense), barcheek goby (Ctenogobius giurinus), western mosquitofish (Gambusia affinis), silver carp (Hypophthalmichthys molitrix), and mud carp (Cirrhinus molitorella), with relatively similar total lengths, were selected as potential prey based on their availability and habitat use. Our results show that predation capacity and preference varied quantitatively and qualitatively among prey species. The number of oriental river prawns killed was significantly less than that of fish species, comparing the 1st hour with the 24th hour (p < 0.01). The feeding rhythm of LB varied significantly from crayfish to fish. Numerically, Jacobs' selection index reinforced LB's special preference for predating G. affinis. Although there were obvious variations in predation capacity and feed selection, no statistically significant growth differences were detected among LB groups feeding on live M. nipponense, G. affinis, H. molitrix, and C. molitorella (p < 0.05). These findings suggest that the successful ontogenetic dietary shift of juvenile LB may depend on the availability and vulnerability of local fish species. Further study on the reproductive phenology of potential fish prey may help to predict LB's establishment. [ABSTRACT FROM AUTHOR]