Photo-thermal induction of gonadal maturation in completely controlled conditions is still not well explored in pikeperch. Thus, wintering intensively reared breeders in outdoor pond conditions might be rather suitable alternative to use these fish for larvae production. In this study, we compared the propagation success of indoor-reared [recirculating aquaculture systems (RAS)-reared fish, RRF] and wild (WCF) pikeperch females wintering them in outside earthen ponds. Each group was composed of six females and four males which were artificially propagated following hormonal induction with human chorionic gonadotropin. Beside the main parameters of reproductive success, fatty acid composition of dry eggs and mortality during early larviculture were assessed. The only statistically significant difference among reproductive parameters was found in latency time, which was significantly lower in RRF. Fatty acid profiles of dry eggs were rather similar between the groups; however, significant difference was noticed in phospholipid fraction in EPA/AA (eicosapentaenoic acid; C20:5n-3/arachidonic acid; C20:4n-6) ratio which was, on average, five times higher in the RRF (5.1 AE 3.8) than in WCF (0.9 AE 0.3). Significantly lower mortality was seen in the larvae originating from wild breeders (13.4 AE 1.7% and 27.0 AE 4.9% for WCF and RRF respectively). Wintering indoor-reared females in outdoor pond conditions led to appropriate gonadal maturation, and ovulation occurred in all examined females. The lower quality of larvae was likely caused by suboptimal broodstock nutrition, which should be studied further, with special consideration given to the EPA/AA ratio and the phospholipid content and composition of the diet.
This study aimed to estimate the efficacy of two pike-perch juvenile production technologies: exclusive Recirculating Aquaculture System (RAS) culture (the RAS group) and pond larviculture with a transfer to the RAS at the 42nd day post-hatch (DPH). Both direct weaning on dry feed (the Pond-D group) and 10-day gradual weaning using bloodworms (the Pond-B group) after transfer to the RAS were evaluated in pond-nursed fry. Their survival and morphometric indices were monitored after the RAS habituation period (first 10 days), after the 18-day post-habituation period and after an additional 30 days of on-grow. Our results indicate a negative allometric growth of the pond-nursed fish during the nursing period, which was slower (p < 0.0001) in comparison to the RAS-nursed fry (16.3 ± 0.4 vs. 17.8 ± 0.7%/day). After transfer, these fish grew faster than the RAS-nursed fry (7.7 ± 0.1, 4.9 ± 0.5 and 6.1 ± 0.6 during habituation, 8.5 ± 0.6, 9.3 ± 0.5 and 6.7 ± 0.1%/day during post-habituation period, in the Pond-B, Pond-D and RAS groups, respectively). However, four weeks afterwards, the RAS-nursed fry were again superior in terms of growth (4.0 ± 0.1, 3.6 ± 0.2 and 4.6 ± 0.2%/day, for the Pond-B, Pond-D and RAS groups, respectively), and this was accompanied by a significantly lower feed conversion ratio in this group. Although the survival of the RAS-nursed fry during the nursing period was lower in comparison to the pond-reared fry (11.3 vs. 67.3%), the RAS seems to provide a long-term growth advantage.
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