Tahoe Kokanee Oligotrophic System

Posted by George White on 9/19/2007, 12:04 pm

As we get ready to harvest eggs for this years projects, I read the reports of the past studies of Lake Tahoe on the Mysis Shrimp and the Kokanee. Studies by Morgan, Threlkeld and Goldman in 1978 indicate these results: Lake trout (Mac's) were introduced 100 years ago and the Koks in the 1940's. Result big Koks and Macks eating from 21% to 58% of the yearly spawners. After the Shrimp introduction this range was 20% to 48% of Kok spawner populations. The Lake trout eat 7 metric tonnes Kokanee, Cannibalize 22 tonnes of themself,100 tonnes of crayfish,140 tonnes of native fish and 460 tonnes of schrimp. The Kokanee loss is between 23,000 to 34,000 adult fish yearly. Mysis is the most important biomass for lake trout. The conclusion is that Kokanee and native fish (minnow types) are most disturbed and need our help. We have planted up to 300,000 koks in the past and never less than 100,000. We should always plant over 200,000 Koks to keep this fishery as the home waters of Nerka in good balance.

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