RESPONSE TO MASS SELECTION FOR GROWTH-RATE IN OREOCHROMIS-NILOTICUS

Bidirectional mass selection for high (H) and low (L) body weight and total length in Oreochromis niloticus was performed for one generation to study the response to selection for grwoth rate. Thirty males and 30 females were randomly selected from a base population of 1076 fish to represent the control (C) line. High and low lines consisted of the 60 largest and 60 smallest fish, respectively. Three batches of eggs spawned on three different dates were considered separately for growth performance. There was little response to mass selection for growth rate. Realized heritabilities for both high and low lines were, in general, low in all three spawns, indicating that mass selection is not an effective means of improving growth rate in this species. © 1990.