Age, growth and production of the silver crucian carp (Carassius auratus) in a former side arm of the middle River Danube in 1985-1990 in Slovakia
1994
Cerny, J. | Sommer, N. (Slovenska Akademia Vied, Bratislava (Slovakia). Ustav Zoologie)
From 1985 to 1990, the age, growth production index, total and available production of silver crucian carp Carassius auratus per year and vegetation period were studied in a Danube arm near Trstena na Ostrove, river km 1925.5. The population consisted of fish aged 0+ to 8+, with growth in individual years differing only slightly. Condition was well-balanced, as indicated by K - values (Bertalanffy's equations), by coefficient b (GM length-weight equations), and by evaluating differences in relative growth increments. The growth rate was similar to that in the Morava, Ipel and Dyje rivers. A higher growth rate was observed only in the Danube Delta. A statistically significant correlation was found between the true mean growth rate (G=aS sup(b)) in weight of silver crucian carp and the number of days water flowed through the side arm (r sup(2) values: age group III = 0.952, IV = 0.977, V = 0.958). Production index values for 2+ to 6+ age classes ranged from 714 to 819 g. Total production (P sub(T)) ranged from 27 to 46 kg.ha** (-1) and 40 to 190 kg.ha** (-1) per vegetation period. Age class IV contributed most to P sub(T) (33.8-51.2 %). The P sub(T)/P sub(A) coefficient was 0.790 for both growth periods and for the entire year. The average values of the turnover coefficients P sub(T)/B and P sub(A)/B were 0.396 and 0.316 for the vegetation periods, and 0.383 and 0.481 for the entire year respectively. The growth and production indices confirm the higher ecological plasticity and adaptability of silver crucian carp to a changeable environment.
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