An Assessment of Key Biological Resources in the Delaware River Estuary
Creators: name: No Name Supplied
Publisher: name: No Publisher Supplied
Year: 1991

description: A review of information pertaining to the biological resources in and around the Delaware estuary was initiated at the request of the Delaware Estuary Program. Based upon an initial review of published information, key biological communities and species were identified for this estuary. Determinations of which communities and species were key resources were based upon ecological importance, significance to commercial or recreational fisheries, and designations of endangered, threatened, or protected status. Using these criteria, seven biological communities and 40 species were determined to be key biological resources within the Delaware estuary.Using additional information from published and unpublished sources, the current status and historical trends for each community and species were described. Where possible, information was assembled and presented for three regions of the estuary which had distinct physical and chemical characteristics and different pollution histories. These regions were:• Delaware Bay Region -- from the mouth of the bay (rkm 0) to Artificial Island (rkm = 80); characterized as having waters with marine to brackish oligohaline salinities.• Transition Region -- from Artificial Island (rkm « 80) to Marcus Hook, PA (rkm « 130); characterized as a low salinity, high turbidity region with a long history of repeated impacts from contaminant loadings.• Tidal Fresh Region -- from Marcus Hook, PA (rkm = 130) to Trenton, NJ (rkm = 220); the fresh water portion of the estuary that is influenced by the tides.Information was available to describe status and trends for the major biological communities in all three regions of the estuary. However, most of the longer term, more detailed studies were completed in the bay region of the estuary. Status and trends information for birds could not be presented by estuarine region because of their broader distribution around the estuary.More information was available to describe status and trends for commercially important species and communities containing commercially important species than for other species and communities. Quantitative information to describe historical trends for fish and shellfish species, for example, were available back to 1880. Shorter-term (about 30 years) quantitative datasets were located for bird species.Historical trends for the biological resources of the Delaware estuary are associated with human activities in and around the estuary. For example, overfishing and other fishery related activities appear to have been the cause of the decline in sturgeon at the turn of the century and oysters in the 1940's. Declining water quality as a result of intense urbanization and industrialization, mostly in the transition and tidal fresh regions of the estuary, are linked to reductions in anadromous fish stocks such as alewife and shad. Improvements in water quality in recent years (mainly dissolved oxygen concentrations) are associated with the return of these and other fish species to the estuary. Regulatory control of DDT and other chlorinated pesticides appears to be a principal cause of recent increases in raptors such as the bald eagle, osprey, and peregrine falcon, all of which suffered great declines in the 1960's.This assessment suggests that nearly all of the biological communities living in or around the Delaware estuary are key biological resources and deserve attention. However, although all communities may be important, all species are not. Important species tend to be those that are valued by man specifically as a result of their commercial or recreational value, aesthetic qualities, or perceived importance.