Influence of survey design on juvenile fish community metrics: Implications from a study in Chesapeake Bay tributaries

Aquatic resource surveys that span multiple decades provide valuable information about fish population responses to environmental and human-induced changes.  Often, surveys are altered as scientific objectives change or in response to management needs.  These modifications result in inconsistencies in the time series, which must be addressed for proper analysis of fish community data.  Since 1996, juvenile fishes in Virginia tributaries of Chesapeake Bay have been captured monthly using a bottom trawl at both fixed and random stations.  Prior surveys (1955-1995) were conducted at fixed stations only, thus an understanding of the effect of this design change would allow us to infer fish population status through multiple decades.  We compare samples taken with the fixed station design versus the stratified random design in the James, York, and Rappahannock rivers and examine species composition, relative abundance estimates, and size distributions to understand how survey design affects our understanding of juvenile fish recruitment.  Combined catch results from random stations had consistently higher species diversity than those from fixed stations. Relative abundance estimates of select species showed similar trends among survey designs, but differed in magnitude among years and rivers.