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Abstract

The following proofs of Goldfish more powerful reproductive potential are given: high individual and relative fecundity, adequate fractional spawning process resulting in numerous off spring, represented by different generations of hatchlings, little number of individuals not participating in reproduction, prevailing number of fish eggs in females’ ovaries, larger fraction of impregnated roe. All the above mentioned factors allow claiming that the Prussian carp is being replaced due to its low replacement ability. Perhaps for that reason Carassius gibelio (Bloch, 1782) choose small isolated water bodies, where it makes small populations, backed up by successful spawning with a single male of crucian carp, Carassius carassius (Linnaeus, 1758).

Fecundity Of Vendace, Coregonus Albula (L.), From Several Lakes In Western Pomerania

The aim of the study was to determine individual absolute and relative fecundity in vendace, Coregonus albula (L.), populations from four Western Pomeranian lakes that differ morphometrically and trophically. The highest mean total length and individual weight were recorded in the fish from the mesotrophic lakes Ińsko (229.1 mm and 106.6 g, respectively) and Miedwie (228.1 mm and 105.1 g, respectively). The highest individual absolute fecundity in particular age groups as well as individual relative fecundity were noted in the fish from Lake Miedwie (6635-24620 eggs per female and 10756-11609 eggs per 100 g female body weight, respectively), while the lowest values of these parameters were confirmed in fish from Lake Glinna (4782-6087 eggs per female and 6406-6953 eggs per 100 g female body weight). A high, statistically significant correlation between absolute fecundity and total fish length and a slightly lower correlation between absolute fecundity and fish age were noted in all of the populations studied.

Growth rate and reproduction of a brood stock of European whitefish (Coregonus lavaretus L.) from Lake Gaładuś under controlled rearing conditions

The focus of the study was to analyze the effects of the artificial reproduction of whitefish, Coregonus lavaretus (L.) aged from 1+ to 4+. It was confirmed that males comprised 64.5% of the brood stock. The males were sexually mature at the age of 1+, while most females were mature at the age of 2+. The females gained weight faster in comparison to the males, and the differences were highly statistically significant (P < 0.001). Survival during the period from the first spawning at age 1+ to spawning at age 4+ was 79.6% for males and 59.6% for females. The quantity of eggs obtained, the egg size, and their survival during incubation all increased as the fish aged. The weight of the eggs obtained from fish aged 3+ and 4+ was statistically significantly higher that from younger fish (1+ and 2+) (P < 0.001). The results of the current study indicate that exploiting a whitefish brood stock under controlled conditions can begin as early as at age 2+. The highest relative fecundity and largest egg size were obtained in females aged 3+.

References Bernatowicz S. 1963 - Observations of vendace spawning in the Lake Mamry complex - Rocz. Nauk Rol. 82: 339-352 (in Polish). Cryer M., Peirson G., Townsend C. R. 1986 - Reciprocal interactions between roach, Rutilus rutilus, and zooplankton in a small lake: prey dynamics and fish growth and recruitment - Limnol. Oceanogr. 31: 1022-1038. Czerniejewski P., Filipiak J., Czerniawski R. 2003 - Absolute and relative fecundity in vendace (Coregonus albula L.) from Western Pomeranian lakes - Komun. Ryb. 4: 15-18 (in Polish). Czerniejewski P., Lewita O., OEwi1