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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 spawn - ing 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 spawn - ing 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.

Quality of semen and histological analysis of testes in Eurasian perch Perca fluviatilis L. during a spawning period