ABSTRACT
This chapter presents the application of a regional reference approach used in a watershed-specific assessment in southern Pennsylvania. It utilizes a contemporary multimetric approach for biological assessments based on comparisons of Codorus Creek biological condition with ecoregional reference conditions. An assessment of physical habitat characteristics was made concurrently with the macroinvertebrate and fish biosurveys. The key to reducing subjectivity in visual-based approach is to provide adequate training and address relevant parameters that represent the physical habitat structure of the region. Benthic macroinvertebrate sampling consisted of a multihabitat composite from each station. The field technique was standardized by unit area to insure comparable effort at all sites, and followed a method developed for low-gradient streams. Fish collection techniques were standardized to provide a representative sample, ensure data quality, and allow a comparison of fish assemblages along the length of the study area. Macroinvertebrate IBI scores demonstrated considerable overlap among the population of upstream and downstream sites.
