Impact of the Introduction of Kokanee (Oncorhynchus nerka) and Opossum Shrimp (Mysis relicta) on a Subalpine Lake

Publisher Website
Google Scholar
Abstract
Introduction of oppossum shrimp (Mysis relicta) and kokanee salmon (Oncorhynchus nerka) are common management tools for improvement of local sprot fisheries. Published information from varied sources was summarized and supplemental data on the impact of these introductions on the Lake Tahoe [USA] zooplankton and fish communities presented. Concomitant with peak spawning runs of kokanee and the establishment and high densities of Mysis was the disappearance of the 3 pelagic cladoceran species in the lake. Population dynamics analysis of the cladoceran populations indicated that their elimination was due to increasing death rates (related to Mysis and kokanee predation) and decreasing birth rates (possibly related to cultural eutrophication). Changes were observed in the fish populations. Lake trout altered their food habits to include large quantities of Mysis, but this was done to the exclusion of other prey types. Improvement in lake trout condition was indicated only in yr when Mysis was abundant. Recent evidence of a sustained decline in the mysid population suggested that unless lake trout shifted back to more traditional food sources, their condition could deteriorate to below pre-mysid levels. Mean wt and abundance of kokanee spawners declined after the cladoceran disappearance, suggesting a negative impact on the whole population which fed heavily on cladocerans.

This publication has 4 references indexed in Scilit: