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Inovace chovu larev candáta obecného (Sander lucioperca L.) při použití vířníků druhu Branchionus plicatilis
IMENTAI, Aiman
Pikeperch (Sander lucioperca L.) has been realized as one of the promising candidates. Currently one of the crucial bottlenecks in pikeperch larviculture is larval first feeding when high mortalities occur. Since recognition of rotifers as potential candidate for larvae culture, its value has grown tremendously in fish hatcheries. Although using rotifers and Artemia as a starter food items has become a common practice in hatcheries, yet rotifers has not been used for pikeperch larval culture. Many questions regarding introduction of rotifers during pikeperch larval first exogenous feeding are still not answered. The aim of this Ph.D. thesis was to maximize survival, growth and fitness of pikeperch larvae during first exogenous feeding by using rotifers Brachionus plicatilis. The effects of B. plicatilis on survival rate, growth performance and fitness of pikeperch larvae during first feeding were evaluated in the first study. Larvae were reared under three different diets (Artemia; Art /rot; rotifers) from 3 till 17 days post hatch (DPH). Using rotifers as first diet for pikeperch larvae was shown to benefit survival and growth rates. Larvae fed on rotifers only or combined diet (rot/Art) obtained higher survival and growth compared to Artemia diet. It was found that essential fatty acids of rotifers and their smaller size had a crucial effect on the larval survival and performance. The findings of the first study showed that the mixed diet (rot/Art) could be recommended as innovated first exogenous feeding in pikeperch larvae. The objective of the second study was to optimize the first exogenous feeding regime for pikeperch larvae using rotifers and Artemia. Larvae were fed with rotifers for 3 days and afterwards from 8 to 17 DPH they were adopted to 5 different regimes. It was found that feeding pikeperch with rotifers from 5 to 8 DPH and afterwards exclusively with Artemia or mixed of rotifers and Artemia till 17 DPH can ensure high survival and growth rates, and better development of digestive organs. Feeding larvae with rotifers from 5 to 8 DPH and afterwards replacing with Artemia till 17 DPH is recommended as an optimum feeding regime because larval survival and growth were satisfying, and it reduces the costs for production. The main aim of the third study was to determine the optimal salinity for rearing of pikeperch larvae using B. plicatilis. Rotifers were stocked under different salinities and motility was investigated over a 6-h period. The same salinities were used in second trial of this study to quantify the effect on pikeperch gut fullness over the course of 11 h. In the third trail, the survival and growth rate of larvae from 4 to 11 DPH at low and medium salinities were analyzed. Results of this study showed that rotifers stocked at all tested salinities, except for freshwater retained motility for over a 6-h period. Pikeperch larvae reared at 2? and 4 ? showed higher survival and growth rate during trial compared to freshwater. The results of this study showed that larvae in low salinity water had higher survival and growth rate during initial exogenous feeding with B. plicatilis. The aim of fourth study was to determine the optimal rotifers density for pikeperch larvae at the beginning of exogenous feeding. Larvae were divided into 4 groups at different rotifers densities from 5 to 9 DPH. The best growth performance was achieved at the highest rotifers density, however survival rate did not significantly differ among the groups. The results suggested that B. plicatilis at density of 6 ind/mL can be considered optimal for larval growth from 5 to 9 DPH when balancing production and costs, compared to higher prey densities.
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