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Wednesday, January 30 • 10:20am - 10:40am
(FISHERIES: TECHNIQUES) Using Measures of Precision and Catch to Estimate Sample Size Required to Meet Sampling Objectives for Standard Sport Fish Assessments

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AUTHORS: Stephen M. Tyszko, Jeremy J. Pritt, Joseph D. Conroy –Ohio Division of Wildlife

ABSTRACT: Using standard sampling methods for sport fish assessment allows powerful comparisons across time and space, if sample size is adequate. Biologists have begun evaluating precision and catch of sport fish surveys using North American standard methods (NASM) and have used resample methods to estimates sample sizes required to meet precision and catch objectives. The Ohio Division of Wildlife has collected standard sport fish surveys since 2003, providing an opportunity to further understand the performance of these methods. We evaluated relative standard error (RSE) and catch of stock-length individuals for NASM Largemouth Bass Micropterus salmoides electrofishing surveys  and NASM crappie (Pomoxis spp.) fyke net surveys in Ohio reservoirs 2003–2017.  We then used resampling methods to estimates sample sizes required to meet two sampling objectives: (1) for CPUE, achieve an RSE = 25; and, (2) collect at least 100 stock-length fish. We found that Largemouth Bass and crappie surveys generally met sampling objectives.  Resample analysis showed that the median number of samples required to meet objectives for Largemouth Bass surveys was 12 or fewer and the median for crappie surveys was 20 or fewer.  Our results support literature that shows NASM electrofishing can be used to obtain precise Largemouth Bass samples that meet catch objectives with a reasonable sample size.  Our crappie survey results contrasted literature that shows NASM fyke net methods required prohibitively large sample sizes to meet precision and catch objectives.  This analysis advances our understanding of sample size requirements for standard methods and highlights the importance of estimating sample size when designing standard surveys. Furthermore, we propose a standard resampling method for estimating sample size requirements.    

Wednesday January 30, 2019 10:20am - 10:40am

Attendees (12)