Andrzej Kompowski, Zbigniew Neja
Agricultural Academy in Szczecin, Kazimierza Królewicza 3-4, 71-550 Szczecin, Poland
Key words: Aspius aspius, asp, growth rate, back-calculation, Oder River.
Juvenile specimens of asp (0 age group) were collected in 1996-2001 in canals of the Międzyodrze with fine-mesh fry seine. Adult specimens were collected from commercial catches in 1995-2003. The length of fish at which scales began to appear (SL = 13.81 mm) was determined using the dependence between the number of sclerites on the caudal part of the scale and the standard length. A similar result of 13.41 mm was obtained in studies of the dependence between the scale radius and fry body length. The average lengths in subsequent years of life were determined by reconstructing the growth rate of the studied fish using back-calculations from scales. The differences in the growth rate of females and males were statistically insignificant. The von Bertalanffy growth model was fitted to the data from the back calculations and the following values were obtained: L∞ = 75.24 cm; k = 0.165; t0 = 0.224 year; W∞ = 7 463 g. The length-weight dependence can be described as W = 0.0075 L3.1964. The growth rate of asp from Międzyodrze waters is average in comparison with that of other populations of this species.