Eradication of non-native fish from a small mountain lake: gill netting as a non-toxic alternative to the use of rotenone.

Abstract

Nearly all mountain lakes in the western United States were historically fishless, but most now contain introduced trout populations. As a result of the impacts of these introductions on ecosystem structure and function, there is increasing interest in restoring some lakes to a fishless condition. To date, however, the only effective method of fish eradication is the application of rotenone, a pesticide that is also toxic to nontarget native species. The objective of this study was to assess the effectiveness of intensive gill netting in eradicating the trout population from a small subalpine lake in the Sierra Nevada, California. We removed the resident trout population and a second trout population accidentally stocked into the study lake within 18 and 15 gill net sets, respectively. Adult trout were highly vulnerable to gill nets, but younger fish were not readily captured until they reached approximately 110 mm. To determine the utility of gill netting as a fish eradication technique in other Sierra Nevada lakes, we used morphometry data from 330 Sierra Nevada lakes to determine what proportion had characteristics similar to the study lake (i.e., small, isolated lakes with little s p awning hab i t at). We estimated that gill netting would be a viable eradication method in 15-20% of the high mountain lakes in the Sierra Nevada. We conclude that although gill netting is likely to be more expensive and time consuming than rotenone application, it is a viable alternative under some conditions and should ...

Citation

Knapp, R.A. and K.R. Matthews. 1998. Eradication of non-native fish from a small mountain lake: gill netting as a non-toxic alternative to the use of rotenone. Restoration Ecology 6:207-213.