Background Information

trafficWith proximity to the nation's capital, and surrounding metropolitan areas and desirability as a playground, Maryland's portion of the Chesapeake Bay watershed is rapidly developing. Fisheries researchers and managers are becoming more aware of the effects of growth on the living resources of the Bay and the small rivers and streams that flow into the Bay.

Maryland Department of Natural Resources, Fishing and Boating Services initiated studies examining impacts of land development on fisheries in the Bay. These studies indicated that when impervious surface (rooftops, roads, sidewalks, parking lots and compacted soils) covers 10% or more of a watershed, fish habitat is significantly impaired and fish populations decline.

effectsOur study of yellow perch in Severn River described the impact of urbanization on its biology. This study suggests that reproduction failed because adults no longer produced enough viable eggs, larvae, and juveniles. Spring salinity in the nursery was much higher than historic data suggested, probably because the stream function changed as land in the watershed was developed. Late spring and summer dissolved oxygen conditions were so poor over much of the river that adult female yellow perch exposed to this habitat were stressed.

Other research has shown that contaminant levels in white perch in Chesapeake Bay tributaries increased with impervious surface (King et al. 2004). This is reflected by increased fish consumption advisories issued in urban areas.

larvalPlanners should recognize degradation of fish habitat with development as they deal with infrastructure issues and they should be aware that watersheds with 10% or greater impervious cover have poor fish habitat. We recommend that land-use planning agencies consider a margin of safety (plan for no more than 8% impervious surface) in less developed watersheds slated for growth in order to protect these valuable resources. From the fisheries management perspective, our studies indicate that standard management options (stocking and harvest restrictions) cannot overcome degraded habitat once the 10% threshold is exceeded.


King, R.S., J.R. Beaman, D.F. Whigham, A.H. Hines, M.E. Baker, and D.E. Weller. 2004. Watershed land use is strongly linked to PCBs in white perch in Chesapeake Bay subestuaries. Environ. Sci. Technol. 38:6546-6552.