Fisheries Institute in Olsztyn, PolandCitation: Koz³owski M., Szczepkowski M., Wunderlich K., Szczepkowska B., Piotrowska I. 2014 -Polyculture of juvenile pikeperch (Sander lucioperca (L.)) and sterlet (Acipenser ruthenus L.) in a recirculating system -Arch. Pol. Abstract. The experiment examined the possibility of rearing juvenile pikeperch, Sander lucioperca (L.) in polyculture with sterlet Acipenser ruthenus L. in a recirculating system. Three variants of pikeperch rearing were tested: monoculture (group S), with the addition of sterlet at 10% (group S10) and 20% (group S20) of the initial pikeperch biomass. After 56 days of rearing, no differences in the growth rates or survival of the pikeperch were noted. The value of the feed conversion ratio in the monoculture group was 1.19 and was significantly statistically higher than in the polyculture groups, the values of which were 0.84 (S10) and 0.74 (S20). The mean oxygen consumption and ammonia excretion values did not differ significantly statistically among the studied groups. Including the sterlet stock with the pikeperch permitted obtaining the additional value of the sterlet biomass using the same quantity of feed. Additionally, the inclusion of sterlet decreased the labor intensity of pikeperch rearing since the tanks did not need cleaning as frequently.

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Summary ― Three feeding groups were used: the control (SOY) was fed diets without rapeseed products, and the two experimental groups were fed with either 10% rapeseed meal (RSM) or with 12% 00 rape seeds (PFRS). Half of the boars from each group were slaughtered after I or 2 years. In RSM and PFRS boars steroid-3-beta-ol-dehydrogenase activity was high, whilst Leydig cells were not numerous after 1 year. Degeneration and necrosis of seminiferous epithelium resulting in atrophy of seminiferous tubules appeared in RSM boars after 2 years. In the PFRS group the lesions were stronger and proliferation of Leydig cells with high steroid-3-beta-ol-dehydrogenase activity was observed. In 1-year-old RSM and PFRS boars there were foci of necrosis in the epididymal epithelium. Thyroid weight in RSM boars and liver weight in PFRS boars were distinctly higher only during the first year. In these thyroid glands flattening of glandular epithelium and enlargement of colloid masses were observed, while in the livers, parenchymatic degeneration and structural transformation appeared. Testis weight increased after 2 years in RSM and PFRS boars; however, this had little effect on semen production.

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This study identifies the possibility of using visible implant elastomers (VIE) to tag juvenile Atlantic sturgeon (Acipenser oxyrinchus). The mean body weight was 2.4 AE 0.4 g, and mean body length 5.5 AE 0.5 cm. Markers in three colours were used: blue, orange and green. Implant elastomers were injected in the rostrum and in the tail shaft. The experiment was conducted over a period of 10 weeks and included also a control group, that is, no tagging. No significant effect of tagging on the specific growth rate, feed conversion ratio and condition factor of juvenile Atlantic sturgeon was observed. The fish in all groups increased their body weight more than 10 times, reaching body weight of 25-28 g. The final survival in all of the groups was approximately 40%. The final tag retention varied depending on the implant colour. The highest retention of 100% was obtained with orange VIE and was significantly different from blue and green. Tag retention was dependent on the place of marking (P > 0.05). A correlation was observed between the applied dye and the place of marking (P = 0.0166). The best results were obtained when marking with orange VIE in the rostrum as all markers were visible after 70 days even without the use of UV light. According to our research, marking with VIE does not negatively affect growth and survival of juvenile Atlantic sturgeon and can be recommended for fish with an initial body weight of approximately 2.5 g in the case of short-term research.

Abstract. The aim of this experiment was to assess the impact live and formulated diets had on the growth and survival of larval Atlantic sturgeon, Acipenser oxyrinchus Mitchill. In the first experiment, the results of feeding the fish decapsulated (group D) and undecapsulated (group ND) Artemia sp. cysts were compared. Increases in the body weights and lengths of the fish fed decapsulated and undecapsulated Artemia sp. were similar at values that were not statistically significant. Survival in the larval group fed undecapsulated Artemia was higher in comparison to the group fed decapsulated Artemia (95.0 and 82.8%, respectively). In the second experiment, three commercial starter feeds were used: Aller ArtEX (Aller Aqua, Poland; group A), Nutra HP (Skretting, France; group H), and Perla Prolarvae (Spa Hendrix, Italy; group P). Following 35 days of culture, no differences were noted in fish growth with lengths in the different groups ranging from 28 to 30 mm and weights from 119 to 134 mg. Fish survival in group A was 55% and was significantly statistically higher than that in groups H and P at 31.7 and 35.7%, respectively. The results of the experiment suggest that the best feed for the early stages of Atlantic sturgeon culture is undecapsulated Artemia during the beginning of exogenous feeding followed by an Artemia-based feed in the initial period of feeding with formulated diets.

Fisheries Institute in Olsztyn, Poland Citation: Szczepkowski M., Zakêoe Z., Kapusta A., Szczepkowska B., Hopko M., Jarmo³owicz S., Kowalska A., Koz³owski M., PartykaK., Piotrowska I., Wunderlich K. 2012 -Growth and survival in earthen ponds of different sizes of juvenile pike reared in recirculating aquaculture systems -Arch. Pol. Fish. 20: 267-274.Abstract. The aim of the study was to determine the growth and survival of juvenile pike, Esox lucius L., reared in recirculating aquaculture systems (RAS) and then released into earthen ponds. Three different sizes of fish were used in the experimental releases of stocking material with mean body weights of 1.5 g (group S), 7.0 g (group M), and 18.5 g (group L) which were reared in a recirculating aquaculture system and fed formulated feed exclusively. Before the fish were released, they were tagged with visible implant elastomer (VIE) tags. The highest final body weight was attained by the fish in group S, the mean body weight of which was 85.5 g, which was significantly statistically higher than in the other groups (P < 0.001). No differences in survival were noted among the groups. Positive biomass increases were only exhibited in group S (37 kg ha -1 ), and it was highly statistically significantly greater than it was in the other groups (P < 0.001). The results of the experiment could indicate that the suitability of juvenile pike for stocking depends on its size at release. Extending the rearing period in RAS resulted in poorer stocking results in the ponds.

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