Reversing introduced species effects: experimental removal of introduced fish leads to rapid recovery of a declining frog

Published source details Vredenburg V.T. (2004) Reversing introduced species effects: experimental removal of introduced fish leads to rapid recovery of a declining frog. Proceedings of the National Academy of Sciences of the USA, 101, 7646-7650.
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This study is summarised as evidence for the following.

	Action	Category
	Remove or control fish by catching Action Link

Remove or control fish by catching

A replicated, controlled, before-and-after study in 1996–2005 of 21 lakes in California, USA (Vredenburg 2004) found that mountain yellow-legged frogs Rana muscosa increased following fish removal. One year after removal, numbers had increased for frogs (0.1 to 1.0/10 m) and tadpoles (0.1 to 8.1). Following removal, numbers were significantly greater than in lakes with fish (frogs: 0.1; tadpoles: 0.1/10 m). Within three years there was no significant difference between numbers within removal lakes and fishless control lakes (frogs: 7 vs 5; tadpoles: 10 vs 30/10 m). Trout Oncorhynchus mykiss, Salvelinus fontinalis were eliminated from three, and greatly reduced in two, removal lakes. Fish were removed by gill-netting starting in 1997–2001. Frog visual encounter surveys along shorelines and snorkelling surveys were undertaken in trout removal lakes (n = 5), fish-containing lakes (n = 8) and fishless lakes (n = 8) each two weeks in 1997–2001 and 2–3 times in 2002–2003.