Current Status and Future Prospects for Freshwater Fishes of Conservation Concern in Maryland

Urban areas in 1992 (top) and predicted increases to 2020 (bottom) for the state of Maryland. Freshwater fishes are among the most imperiled groups of organisms in the United States.  The World Conservation Union estimates that 34% of fish species, mostly freshwater, are currently threatened with extinction. For many species, the cause of imperilment is complex, but can usually be traced to altered habitat or pollution induced by human alteration of watersheds.

Currently, over 75% of the US human population lives in urban areas and that percentage is expected to increase. Maryland's population is predicted to increase by over 1 million people by 2030. The objective of this project was to identify current distributions of freshwater fishes of conservation concern, identify linkages with human populations, and predict future fish distributions in response to future human growth.

We used Maryland Biological Stream Survey data collected between 1996 and 2004 to determine current distributions of target species. Using Geographic Information Systems (GIS) and statistical modeling, we determined relationships between fishes, land use, stream conditions, and human population sizes. We then forecasted our relationships in response to predicted future human population growth in Maryland.

Watersheds containing one or more fish species of conservation concern in Maryland. Watersheds predicted to become unsuitable for one or more fishes of conservation concern.Results from our analysis demonstrate that many of the target fishes were negatively affected by factors associated with human population growth, including with but not limited to increases in impervious surfaces in watersheds, increases in chemical pollutants in streams like nitrate-nitrogen, and increases in surface water temperatures.

Changes in predicted distributions were not as drastic as expected but this may be due to the fact that many sensitive fish have already been eliminated from much of their historic range in Maryland.

Most of the watersheds that are predicted to become unsuitable are located on the Coastal Plain, where 4% of the watersheds are affected. Two percent of the watersheds in the Piedmont physiographic province will also become unsuitable. Few watersheds elsewhere are predicted to become unsuitable for the selected set of fishes. However, this does not mean that there will be no effects since there are >70 other fish species and we looked only at urbanization and not at other factors.

To Learn More:

  • ASTERS Project - Alternate States, Thresholds, & Ecosystem Resilience in Streams

Project PI's:

  • Dr. Bob Hilderbrand 
  • Ms. Amanda Hern