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United States Department of Agriculture

Agricultural Research Service

Research Project: UNDERSTANDING AND PREDICTING THE IMPACT OF AGRICULTURE ON THE ENVIRONMENTAL INTEGRITY OF MANAGED WATERSHEDS

Location: Water Quality and Ecology Research

Title: Bias Associated with Sampling Interval in Removal Method for Fish Population Estimates

Authors
item Knight, Scott
item Cooper, Charles

Submitted to: Journal International Environmental Application and Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 22, 2008
Publication Date: September 22, 2008
Citation: Knight, S.S., Cooper, C.M. 2008. Bias Associated With Sampling Interval in Removal Method for Fish Population Estimates. Journal International Environmental Application and Science, 3(4): 201-206.

Interpretive Summary: Fish population size is one of the most important pieces of information necessary to manage a sports fishery. There are many ways to estimate population size; all having strengths and weaknesses. This research examines one common way of estimating fish population size and suggest ways if improving the accuracy of the estimate. Results of this research will help both state and federal fisheries biologist make precise and accurate estimates of fish populations and thus improve their ability to manage these valuable resources.

Technical Abstract: Population abundance is a fundamental parameter of fisheries science. Accuracy of estimation of population size based on removal methods depend upon on the relationship between catch per effort, cumulative catch and specific underlying assumptions. A study was conducted to determine if increasing the length of interval between electrofishing passes reduce bias in estimates of population size. Four stream reaches were repeatedly sampled by electrofishing at 15, 30, 60 or 120 minute intervals. Electrofishing was followed by a population census in order measure total numbers and biomass of fish present. Percent differences in estimated and measured numbers and weights of fish were calculated for each sampling interval. The 15 minute interval sampling resulted in percent differences between observed biomass and estimated fish biomass that were significantly higher than all other sampling schemes. The high 15 minute interval average difference was followed by a lower difference for the 30, 60, and 120 minute intervals as might be expected if fish "forgot" the electrofishing experience as time increased between runs.

Last Modified: 4/24/2014
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