Ecosystem changes drive modifications to fish diets and trophic interactions in Lake Kinneret, Israel

The Lake Kinneret (Sea of Galilee) ecosystem has undergone physical and biological changes over the past 25 years, including a shift from a dinoflagellate Peridinium gatunense)-dominated system to one in which Cyanobacteria play a major role. The Saint Peter's fish, Sarotherodon galilaeus, the most valuable commercial fish in the lake, was a prime consumer of P. gatunense. Sarotherodon galilaeus has adapted to the ecosystem changes and the scarcity of its primary food source, affecting interactions with other fish in the lake, such as the stocked silver carp, Hypophthalmichthys molitrix. To examine the food habits of the two fish species following the changes in the lake, a total of 300 S. galilaeus and 150 H. molitrix individuals were randomly collected over a five-year period from various places and times in Lake Kinneret. The contents of their stomachs were identified and analyzed. Results showed that a major dietary shift from herbivory to omnivory has occurred since the 1970s in both S. galilaeus and H. molitrix, with H. molitrix now preying almost exclusively on zooplankton. As a result of the dietary changes, both species have had to compete with other fish species for the limited zooplankton resources present in the lake, as well as contending with Cyanobacterial blooms. These changes in the lake's food web require modifications in the management of the lake and its fisheries.

Automated summary

The Lake Kinneret ecosystem has undergone significant changes, with a shift from dinoflagellates to Cyanobacteria as the dominant species. This shift has affected the food habits and interactions of fish species in the lake, such as the Saint Peter's fish and silver carp. The dietary changes, from herbivory to omnivory, have led to competition for limited resources and challenges from Cyanobacterial blooms, requiring modifications in lake management and fisheries.