Competence of Non-random Electrofishing Sampling in Assessment of Structural Indices

Electrofishing for largemouth bass (Micropterus salmoides) in sites selected because they are judged to have habitat favored by bass can often yield higher catch per effort than in sites selected randomly, resulting in reduced effort or more precise estimates. Although samples selected subjectively could misrepresent relative abundance, they mayor may not affect population indices derived from lengthweight data, such as length-frequency and condition indices. We compared indices obtained at randomly-selected sites with indices obtained at subjectively-selected sites. The latter sites provided more largemouth bass, overestimated Proportional Stock Density and Relative Stock Density (P < 0.05), but did not affect Relative Condition (P > 0.05). We conclude that judgment sampling may misrepresent a largemouth bass population's abundance and structure.

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