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A total of 150 pikeperch individuals caught in 1998 in the Pomeranian Bay were examined. The fish were picked out from 4 samples: 3 were obtained in March and 1 in April 1998. The standard methods of length and weight growth rate determination were used. When determining fish age, the verge coefficient was factored in (if Kr > 0.50, 1 was added to the scale annual ring count).
Background. Due to its economical importance the vendace has been considered one of the most important items of the ichthyofauna of Polish lakes. This is mainly because of favourable biological features of this species, namely: short (2-3 years) period of attaining market size, relatively fast growth rate, schooling behaviour facilitating catches, and most of all the high meat value, making it a desirable consumer item. Materials and Methods. Biological characters were determined in 451 vendace from Lake Miedwie, caught in spring, (124 individuals), summer (132), late summer (87), and autumn (108). The age and growth rates of the fish were determined based on scales using commonly accepted methods. Fulton- and Clark coefficients were used to determine the fish condition. Results. The fish caught were 180-294 mm-long (TL) and weighed 45.2-176.3 g. Mean values of the Fulton coefficient indicated a pronounced improvement in the fish condition from spring to later summer (0.70 and 0.80, respectively) and a slight reduction in autumn (0.75). The age composition of the fish was as follows: 1+, 213 individuals (47.2%); 2+, 229 ind. (50.8%); 3+, 9 ind. (2.0%). The von Bertalanffy equations that describe theoretical growth of the fish examined in length (Lt) and weight (Wt), were calculated. Conclusion. According to the generally accepted criteria of the vendace growth rate, the Lake Miedwie individuals showed a very good growth, higher than that recorded in populations inhabiting other whitefish lakes of Polish Western Pomerania, which indicates the availability of appropriate food resources for the vendace in the Miedwie.
The study involved analysis, performed with standard methods, of length and weight growth of 202 perch individuals caught in November 1999 from the Szczecin Lagoon. The verge coefficient was factored in both when determining the age distribution and when analysing length and weight growth by calculating mean values in age groups (when Kr > 0.50, the number of annual rings was increased by 1).
The study involved crucian carp harvested in various seasons of 2000-2002 from the Szczecin Lagoon (177 individuals) and from the Leszczyńskie Lakeland (707 individuals). The fish age was determined from scales. The length growth was back-calculated with the scale radius-corrected Vovk method in which the standard length was set at 12 mm [10]. In addition, 5 mathematical growth models (Ford-Walford, von Bertalanffy, Gompertz, the second order polynomial, and modified power function) were applied. The weight growth was followed by means of the modified von Bertalanffy equation.
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