WEIGHT-LENGTH RELATIONSHIP AND THE CONDITION FACTOR FOR THE GRASS CARP (Ctenopharyngodon idella) WITH DIFFERENT DIETS

Abstract

Ctenopharyngodon idella, known as grass carp, is an exotic species highly appreciated for its performance in fish cultivation. Current analysis was undertaken in the fish culture station of the Universidade Estadual do Paraná in União da Vitória PR Brazil, to assess the effect of three different diets in the development of grass carp fries. A standard initial lot was used, mean weight 13.0 ± 0.58 g and total length 10.0 ± 0.10 cm, distributed in three experimental units of 10 m3 each: (1) fries fed on forage (millet during the summer-spring period and rye-grass during the autumn-winter period); (2) fries fed on forage with commercial meal with 42% crude protein; (3) fries fed exclusively on commercial meal. Results showed significant differences among treatments (p < 0.05), although no statistical difference occurred between treatments with forage only and forage with meal. The weight-length relationship of the treatments followed the equations: y = 0.013x2.990; y = 0.012x3.002; y = 0.018x2.882; growth was allometric (b < 3.0) only for treatment exclusively with meal. There was no significant difference in relative condition factor among treatments (p > 0.05). Although in the case of C. idella growth is better with treatments supplemented with meal, current study showed that treatment exclusively with millet or rye-grass had higher growth rates.