THE EFFECT OF STOCK DENSITY ON THE EFFECTIVENESS OF REARING PIKEPERCH SANDER LUCIOPERCA (L.) SUMMER FRY
Maciej Szkudlarek, Zdzisław Zakęś
The Stanisław Sakowicz Inland Fisheries Institute in Olsztyn, Poland
ABSTRACT. The aim of the experiment was to determine the effect of stock density on the growth, survival and cannibalism of pikeperch fingerlings held under controlled conditions in a water recirculation system and fed an artificial diet. The mean body weight of the fish at the start of the experiment was 0.65 ± 0.11 g and the total length was 4.54 ± 0.28 cm. The fish were divided into three experimental groups with the following stock densities: group A - 0.99 g l-1; group B - 1.65 g l-1; group C - 2.31 g l-1. The rearing period was 42 days long and was divided into the adaptation and rearing proper periods. The results obtained from the experiment revealed that the initial density of pikeperch summer fry, which ranged from 0.99 to 2.31 g l-1, had no effect on the final outcome of the rearing, i.e. neither on growth nor survival (ANOVA, P > 0.05). The final mean body weights for groups A, B and C were 9.43, 9.25 and 8.62 g, respectively, while total losses were 52.5, 56.1 and 56.1%, respectively. The high fingerling mortality during the adaptation period, i.e. from first to the fourteenth rearing day (group A - 40.8%, group B - 50.6%, group C - 44.1%), determined the effectiveness of rearing.
Key words: SANDER LUCIOPERCA, STOCK DENSITY, SURVIVAL, CANNIBALISM
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