Vulnerability of Redbelly Tilapia Fry to Bluegill Predation with Changes in Cover Availability

Abstract

The successful use of redbelly tilapia (Tilapia zilli) to control aquatic plants in ponds with game fish depends on high survival of tilapia young. We tested the vulnerability of redbelly tilapia fry under parental care to predation by bluegill. Experiments were conducted for a 3-day period in 5.5-m diameter pools at three levels of artificial plant cover (25, 50, and 75%) and at two densities of predators (15 and 20 per pool). Predation rates on 14-day-old, unprotected fry also were determined. Fry survival was lowest with 25% cover (mean 40%) and highest with 75% cover (mean 72.5%). The survival of fry at 50% cover (mean 68.2%) was significantly higher than survival at 25% cover, but there was no significant difference in fry survival between 50 and 75% cover. Fry survival was poor without parental care, ranging from 6 to 34%. Extrapolation of the survival data indicated that too few Tilapia zilli, when stocked with predatory game fish, would survive to the size where they could adequately control aquatic plants.