ACOUSTIC ASSESSMENT OF THE NUMBER OF PELAGIC FISH IN LAKE KINNERET, ISRAEL

The pelagic fish stock (mostly lavnun, Mirogrex terraesanctae) of Lake Kinneret was assessed using HADAS, a newly developed echo-counting analysis system. Total fish numbers (during Mar-Apr) were estimated to be 61 million in 1987, 218 million in 1988, 120 million in 1989, and 69 million in April 1990. The total fish number for March 1981 was recalculated from published data and estimated at 170 million. The decline in total numbers between 1988 and 1990 resulted primarily from a decrease in the relative abundance of the smallest size classes of fish. Since fish abundance apparently declined between 1981 and 1990, the decline in zooplankton standing stocks documented during these years cannot be attributed to higher fish predation caused by larger fish stocks. The HADAS estimates of lavnun population size are large enough to account for the known catch of lavnun.