Cichlid Stocking and the Decline of the Galilee Saint Peter's Fish (Sarotherodon galilaeus) in Lake Kinneret, Israel

Abstract

The catch of the Galilee Saint Peter's fish (Sarotherodon galilaeus), relative to the catch of nonstocked fish of Lake Kinneret, has declined since 1958 despite the intensive stocking of S. galilaeus fingerlings. The reduced relative S. galilaeus catch coincides with stocking of the Jordan Saint Peter's fish, S. aureus. Laboratory analyses of S. galilaeus and S. aureus feeding behavior and selectivities suggest that they may compete for zooplankton, a major food resource for both species. The decline of S. galilaeus means not only a relative reduction of the most valuable commercial species but also a disruption of the trophic dynamics of the lake. Sarotherodon galilaeus is the primary consumer of the dominant alga in the lake, the bloom-forming dinoflagellate, Peridinium, and thus is important in maintaining water quality. The impact of stocking practices on S. galilaeus suggests that fisheries policies must be integrated into the overall program of water quality management for Lake Kinneret and lakes in general.