Fishing Mortality and Habitat Loss Affect Largemouth Bass Fishery in the Potomac River (Maryland)

Largemouth Bass Micropterus salmoides is arguably the most popular sport fish of inland waters in the United States. The majority of anglers in the fishery practice catch and release. Catch-and-release guidelines aim to reduce negative impacts of angling on individual fish, though such impacts on populations are not widely reported. We hypothesized that a decline in the population size for Largemouth Bass from a catch-and-release fishery from the Potomac River resulted from a period of greater fishing mortality followed by habitat loss that reduced the recovery of the population. After we analyzed several years of fishery-dependent and independent data (1999-2015), it was determined that fishing mortality and relative exploitation were greater than average in the latter half of the 2000s than in previous years. Fishery-independent survey results suggested a loss of large fish and decline in population size. The relative abundance of juveniles subsequently declined possibly because the area of submerged aquatic vegetation used as nursery habitat had declined after tropical storms. For management purposes, we suggest that fishing mortality not exceed 28% for a sustainable fishery (assuming similar levels of natural mortality) in the Potomac River. Negative impacts to Largemouth Bass populations could be lessened by reduced harvest and widespread enforcement of catch-and-release guidelines, especially during times when angler effort is high, fish are highly accessible to anglers in the fishery, and habitat loss limits recruitment.