Effect of body colour ofOreochromis mossambicus(Peters) on predation by largemouth bass,Micropterus salmoides(Lacepède)

摘要

Abstract.Fifty each of F2‐generation gold (gg), bronze (Gg), and black (GG)Oreochromis mossambicus(Peters) and either zero, four or eight largemouth bass,Micropterus salmoides, (Lacepède) were stocked in 20‐m2concrete tanks. After 7 days, water in all tanks was drained, and fish in each tank were censused. Largemouth bass ate 18 of the tilapia in the four‐bass treatment (1 tilapia/bass/day) and 60 of the tilapia in the eight‐bass treatment (1·6 tilapia/bass/day); the difference was significant (P=0–05). In the four‐bass treatment there was a greater observed mean predation rate on gold than that on black or on bronze tilapia, but the difference was not significant: largemouth bass ate 25 of the gold tilapia, 16 of the bronze tilapia, and 13 of the black tilapia. In the eight‐bass treatment, predation on the gold tilapia was significantly greater than that on both bronze (P=0·05) and on black (P=0·06) tilapia; predation on bronze and black tilapia was similar: largemouth bass ate 80 of the gold tilapia, 48 of the bronze tilapia, and 51 of the black tilapia. Overall average total predation (both treatments combined) on gold tilapia was significantly (P=0·06) greater than that on both bronze and on black tilapia, which did not differ: largemouth bass ate 52 of the gold tilapia, 32 of the bronze tilapia, and 32 of the black tilapia. The increased vulnerability of gold tilapia to predation was a negative pleiotropic effec