Effect of starvation on some of the morphological and haematological parameters of rainbow trout, Oncorhynchus mykiss

In this study the effect of starvation on some morphological (weight and length body; condition factor، liver weight، hepatosomatic index، visceral fat content and tissue moisture) and haematological (plasma glucose; protein; cholesterol; cortisol levels and haematocrit) characters were investigated. After acclimation to experimental conditions، two groups of 45 fish (140±20g)، were assigned to two outdoor concrete ponds (4m × 2. 7 m × 1. 5 m each)، as fed and unfed groups. After commencing the experiment، one group was deprived of food and the second group was fed at the rate of 1. 7 % of bw/ day with a commercial diet. Sampling was carried out at beginning and every ten days intervals up to 60 days after start of the experiment by taking five fish randomly from each group. Results indicate that starvation significantly effects body weight and length; liver weight، and hepato-somatic index (p<0. 05). Despite the great variation and differences in fat content، moisture and condition factor، no significant difference were found among the fed and unfed groups. Nevertheless starvation affected plasma glucose and cortisol level (p<0. 05)، but the protein level was not affected significantly. Although haematocrit values recorded during starvation period showed no significant difference with the initial values، however، a significant differences was found between the fed and unfed groups at the end of the experiment (p<0. 05). Cholesterol level declined initially، so that no significant differences were found between the fed and unfed fish. In conclusion، results indicate a correlation between starvation and some of the morphological and haematological characters، but it was more pronounced with morphological characters which could possibly be justified with a high homeostatic potential of blood.