The studies conducted in 2003^2004 focused on the possibilities of applying a tannic solution to remove adhesiveness from pikeperch eggs. Spawners were caught in Lake Pątnowskie (central Poland) and then transported to the Goszawice Fish Farm. After initial selection, the ¢sh were weighed, measured and stimulated with human chorionic gonadotropin. Gametes were obtained 5 days after the ¢rst injection. The weight and diameter of the eggs, and the commercial fecundity of individual females were determined. The eggs were fertilized with the dry method. After the addition of water, the eggs were mixed for 4 min, and then divided into 20 g portions. After determining the number of eggs in the various portions, the adhesiveness removal procedure was performed. Three concentrations of tannic acid solution (500, 1000, 1500 mg L À 1 ) and three exposure times (0.5, 2,5 min) were applied. The eggs were incubated in Weiss jars. The studies indicated that both the solution concentration and the exposure time sig-ni¢cantly (Po0.05) impacted pikeperch egg hardening, the degree of adhesive removal and embryo survival. The tannic acid solution concentration of 500 mg L À1 applied for 0.5^2 min was not e¡ective; the eggs clumped and it was impossible to separate them even with intensive mixing. Better results were obtained using higher tannic acid concentrations and/or by lengthening exposure time. The adhesiveness of pikeperch eggs disappeared completely after 5 min exposure to tannic acid solution concentrations of 500^1500 mg L À1 or after 2 min exposure to solution concentrations of 1000^1500 mg L À1 . In these variants, the embryo survival rate to the eyed-egg stage was 78.0^84. 0% (2003) and 82.38 4.7% (2004). However, high tannic acid concentration had a negative impact on the pikeperch larvae hatching. The greatest decrease in survival rate was observed in groups exposed to a tannic acid solution of 1500 mg L À1 for 2 and 5 min periods. Thus, the optimum method for removing pikeperch egg adhesiveness was to apply a solution of tannic acid at a concentration of 500 mg L À 1 for 5 min or 1000 mg L À1 for 2^5 min.
ABSTRACT:A qualitative assessment of the Eurasian perch Perca fluviatilis semen describing the basic parameters of seminal plasma was completed. The histological methods used in this study showed changes in perch gonads during a spawning and post-spawning period. At the late period of the spawning season, the structure of testes was clearly loosened and spermatozoa did not fill uniformly all the ampullae of the testes, leaving free spaces at their banks and no spermatids were observed. The results confirmed that there was an additional period after spawning in the annual reproductive cycle of the male Eurasian perch. In both years of investigations (2000)(2001), an essential decline in sperm motility at the late period of the spawning season was observed, from more than 85% to 56% in 2000. The sperm motility was not influenced by sperm concentrations because throughout the spawning time no changes in the sperm concentration were observed, 32.4 and 32.6 mld/ml at beginning and at the late period of spawning period, respectively. In contrast to sperm concentrations, protein concentrations in seminal plasma increased in the late period of spawning season, from 3.95 to 5.16 g/l in 2001. This study confirmed that protein concentrations in the seminal plasma of most fish are much lower than in the other vertebrates. Among the fish examined, perch is characterized by one of the highest values of protein concentrations in plasma. Our observations confirmed that a high water temperature influenced anatomical and functional parameters of the reproductive system in male perch.
The aim of this study was to determine the impact of feeding juvenile pikeperch diets with medicinal herb adjuvants on the growth performance, proximate body composition, fatty acids profile (whole fish, muscle tissues, viscera) and cytological and histological indicators of the liver and middle intestine. The fish (mean body weight of ca. 110 g) were fed diets with a 0.1% supplement of Astragalus radix (group A), Lonicera japonica (group L) or a mixture of these herbs (A. radix+L. japonica; group A/L) for 8 weeks. The herbal supplementation was not noted to have had an impact on the analysed indicators of fish growth performance, condition or feed conversion ratio (P>0.05). Statistically significant intergroup differences were noted in the value of the hepatosomatic index, hepatocyte size, their nucleus and nucleus/cytoplasm diameter ratio (P<0.05). Significant intergroup differences were also noted in the appearance of the hepatic parenchyma. Statistically significant intergroup differences were also noted in the protein content of the whole fish body. The analysis of the proximal composition of the fish viscera, in turn, indicated significant differences in the fat content (P<0.05). Among the analysed group of fatty acids (saturated – SFA, monoenoic – MUFA, polyenoic – PUFA) contained in the whole fish, the fillets and the viscera, significant intergroup differences were noted with regard to SFA (viscera) and MUFA (whole fish) (P<0.05). The total PUFA content was stable, although significant intergroup differences were noted with regard to a few of the acids that belong to this group (P<0.05).
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