MARYLAND BIOLOGICAL STREAM SURVEY - DEVELOPMENT OF A FISH INDEX OF BIOTIC INTEGRITY

As a step towards determining the extent of degradation in non-tidal s treams, a multi-metric Index of Biotic Integrity (IBI) based on fish a ssemblages was developed for the Maryland Biological Stream Survey (MB SS). The MESS is a probability-based statewide sampling program design ed to assess the status of biological resources and to evaluate the ef fects of anthropogenic activities. We used data from 419 MESS sites sa mpled in 1994-95 to develop the IBI. Two distinct geographic strata, c orresponding with ecoregional and physiographic boundaries, were ident ified via cluster analysis and multivariate analysis of variance (MANO VA) as supporting distinctly different species groups. Reference condi tions were based on minimally degraded sites. We quantitatively evalua ted the ability of various attributes of the fish assemblage (candidat e metrics) to discriminate between these reference sites and sites kno wn to be degraded, using statistical tests and classification efficien cy. Provisional formulations of the IBI were selected for each region based on high classification efficiency and broad representation of fi sh assemblage attributes. Fish IBI scores for 1995 MESS sites spanned a wide range of biological conditions, from good to very poor. Over al l six basins sampled in 1995, half of the stream miles fell into the r ange of good to fair. Roughly 25% of stream miles showed some degradat ion. The IBI will be used in conjunction with physical and chemical da ta to answer critical questions about the health of Maryland streams a nd the relative impacts of human-induced stresses on the state's aquat ic systems.