Changes in Mottled Sculpin and Johnny Darter Trawl Catches after the Appearance of round Gobies in the Indiana Waters of Lake Michigan

Abstract

We investigated the response of the mottled sculpin Cottus bairdi and the johnny darter Etheostoma nigrum to the invasion and proliferation of the round goby Neogobius melanostomus at three near-shore locations in southern Lake Michigan. Fish were collected by trawling from June through August, 1984–2002. Mean annual catches of mottled sculpin in trawl samples ranged from 0 to 4.4 fish/h from 1984 to 1998, whereas mean annual johnny darter catches ranged from 0 to 29 fish/h in the same period. Round gobies were first sampled in 1998, and the relative population abundance increased in the following years, ranging up to 371 fish/h at one site by 2001. From 1999 to 2002, only a single mottled sculpin and only 12 johnny darters were collected in 72 h of trawling. This study documents the rapid decline of the mottled sculpin and johnny darter following the round goby invasion to this portion of the lake.