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Providing evidence to improve practice

Individual study: Elimination of brook trout from a mountain lake in Washington resulted in a significant increase in numbers of egg masses and larvae/neotene northwestern salamanders

Published source details

Hoffman R.L., Larson G.L. & Samora B. (2004) Responses of Ambystoma gracile to the removal of introduced non-native fish from a mountain lake. Journal of Herpetology, 38, 578-585

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Remove or control fish by catching Amphibian Conservation

A before-and-after, site comparison study in 1993–2003 of two lakes in a National Park in Washington, USA (Hoffman, Larson & Samora 2004) found that northwestern salamanders Ambystoma gracile increased significantly following elimination of non-native brook trout Salvelinus fontinalis. Day surveys showed that numbers of egg masses increased from 11 to 25–107/150 m and larvae from 5 to 18–90/150 m. Numbers increased to similar to those in the existing fishless lake (egg masses 65–165/150 m; larvae: 57–114/150 m). Night surveys showed a similar pattern with larvae increasing from 72 to 172/150 m and becoming similar to the fishless lake (50–145/150 m). Trout were removed from June to September 1993–2002 using gill nets (42 m long, 2 m tall). One to four nets were set once to several times during a field season. Salamanders were monitored using snorkel surveys along 25 m transects (four nearshore and two offshore) once or twice annually from July to September. Five night and 17–18 day larvae/neotene surveys and 10 egg mass surveys were completed per lake.