Effects of tilapia zilli on growth and survival of fingerling striped bass

Tilapia zilli were evaluated as to the impact on growth and survival of fingerling striped bass (Morone saxatilis) in rearing ponds. Food preference studies indicated the following rankings (most preferred to least preferred) among four naturally occurring vegetational types: fresh naiad, pelleted naiad, chara, alligatorweed, and spatterdock. When evaluating growth of 10.0 to 11.5 g tilapia stocked in tanks and fed vegetation and a commercial ration, the greatest weight gain occurred using trout pellets (0.18 g/day or 90.8%) as compared to fresh naiad (0.01 g/day or 7.3%) and pelleted naiad (-0.03 g/day or -15.4%). Results of feeding tests (one diet) using tilapia and striped bass stocked at five ratios (12:0, 9:3, 6:6, 3:9, and 0:12) indicated that weight gain decreased and mortality of striped bass increased as densities of tilapia increased. When striped bass and tilapia were stocked at a 1:1 (6:6) ratio, striped bass mortality was 50.0% during the 4-week study; growth of striped bass at the same density was 0.11 g/day as compared to the 0.18 g/day of striped bass alone. There were no tilapia mortalities. When comparing tilapia and striped bass at equal densities and fed two diets (trout pellets and fresh naiad), tilapia outgained the striped bass by an average of 99% during the 8-week study. Mortalities of striped bass were 83.3%. Overall results of this study suggest that stocking zilli at densities equal to 30% or less than that of striped bass would be suitable for better growth and survival of striped bass.