Raymond D. Germany

Scales from blue tilapia (Tilapia aurea) captured in gillnets indicated that annulus formation occurred primarily in March and April in 1973 and 1974, but in April and May 1975,. Average back-calculated total lengths of males were 197 and 258 mm at Age I and II and for females 183 and 248 mm. Total population of blue tilapia in December 1974 was estimated as 4,856,963. Of this total 3,120,810 were Age 0 and 1,591,823 were Age I. Biomass of the tilapia population was estimated to be 799,978 kg or 2,640 kg/ha. Survival of blue tilapia from Age I to II was calculated to be 7%. From these...

In the presence of a dense population of blue tilapia, the population of northern largemouth bass declined in three years to one-third its 1972 abundance in Trinidad Lake, Texas. A pond experiment with Florida largemouth bass indicated that bass failed to reproduce sllccessfully at a tilapia density of 2000 Ib/A, but at 1000 Ib/A some bass spawning occurred. Trends in gonosomatic indices suggest that eggs were retained by bass at high tilapia densities.