Deepwater demersal fish community collapse in Lake Huron

Long-term fish community surveys were carried out in the Michigan waters of Lake Huron using bottom trawls from 1976 to 2006. Trends in abundance indices for common species (those caught in 10% or more of trawl tows) were estimated for two periods: early (1976-1991) and late (1994-2006). All common species significantly decreased in abundance during the late period with the exception of the johnny darter Etheostoma nigrum and spottail shiner Notropis hudsonius, which showed no significant trends, and the round goby Neogobius melanostomus, which increased in abundance. Percentage decreases in abundance indices between 1994-1995 and 2005-2006 ranged from 66.4% to 99.9%, and seven species decreased in abundance by more than 90%. The mean biomass of all common species in 2006 was the lowest observed in the time series and was less than 5% of that observed in the mid-1990s. The mean number of common species captured per trawl has also decreased since the mid-1990s. Several factors, including recent invasion of the lake by multiple exotic species, may have contributed to these declines, but insufficient published data are currently available to determine which factors are most important. Our observations suggest that significant changes have occurred in the ecology of Lake Huron since the mid-1990s. The extent of these changes indicates that the deepwater demersal fish community in Lake Huron is undergoing collapse.