The relationship between sampling intensity and sampling error—empirical results from acoustic surveys in Polish vendace lakes

The relationship between sampling effort and the variance of hydroacoustic estimates of fish abundance was studied on the basis of 17 surveys in four lakes. These differed in their morphometric and trophic characteristics, but all contained fish communities dominated by vendace (Coregonus albula L.). Regression between the degree of coverage and the coefficient of variation was produced. The sampling error of abundance estimates was less than 10% at coverage higher than 2 for all the observations. Seasonal changes in fish spatial distribution did not affect the variability significantly. The zigzag survey design gave less variable results than regular parallel transects but the difference was not statistically significant.