Mc. Scott et Lw. Hall, FISH ASSEMBLAGES AS INDICATORS OF ENVIRONMENTAL DEGRADATION IN MARYLAND COASTAL-PLAIN STREAMS, Transactions of the American Fisheries Society, 126(3), 1997, pp. 349-360
Effects of anthropogenic stream degradation on fish assemblages in coa
stal plain streams of Maryland were investigated by using data from 19
89-1993. Fish assemblages, stream physical habitat, and water quality
were assessed concurrently at 69 sites. Through the use of habitat and
water quality information, two groups were selected from the data set
to represent least-impacted streams (N = 16) and most-impacted stream
s (N = 22). Impacts ranged from agricultural activities involving chan
nelization and riparian destruction to altered hydrologic regime and c
hannel modification related to urban development. Differences in fish
assemblages between the two groups indicated that the degraded streams
were less diverse and were dominated by a few tolerant taxa, whereas
higher-quality sites were characterized by a more balanced assemblage
structure and trophic composition, as well as by higher indigenous cyp
rinid richness and abundance. Various metrics, based on assemblage str
ucture and function under a guild approach, were tested for difference
s between the high- and low-quality stream groups. The metrics that ex
hibited the greatest discrimination between groups reflected greater d
iversity and abundance, a balanced trophic structure, and lower abunda
nce of species considered tolerant to environmental degradation. The m
ost effective metrics included the number of intolerant species presen
t, the number of shiner species, the proportion of silt-intolerant spa
wners in the assemblage, the proportion of tolerant fishes, and the pr
oportion of insectivorous cyprinids. The metrics that demonstrated abi
lity to discriminate high- and low-quality streams are proposed for de
velopment into biological indicators for this region.