Monitoring Individual Growth of Tilapia (Oreochromis niloticus and Tilapia zillii) in An Artificially Heated River

摘要

Individual growth of wild tilapia (mixed population of Nile tilapia Oreochromis niloticus and redbelly tilapia Tilapia zillii) was investigated using a release-and-recapture approach in a thermally enriched small river during the period from April toDecember, 2007. Both total length and body weight increased as water temperature increased. When water temperature decreased, the body weight of large fish above 400 g decreased, whereas that of small fish under 400 g showed no change or slight increase.This seasonal growth performance of large fish was also confirmed by the change in the length-weight relationship. A short-term cold shock in early November due to factory shutdown exerted severe adverse effects on the tilapia population, including death; however, the shutdown had no effect on individual growth of survived fish. This study indicated that fish growth was dependent on fish size and season. Additionally, the length-weight relationship was useful when measuring approximate seasonal growthperformance offish despite the small sample size.