Comparison of acoustical estimates of fish abundance for different coverage and survey design

The aim of this paper is to investigate the influence of the degree of coverage, survey design, and method of calculation on fish abundance estimation results. Measurements were performed in deep, mesotrophic lake, containing fish community dominated by vendace (Coregonus albula L.). Two types of survey design were applied: the regular parallel transects with constant distance between them and the triangular (zig-zag) transects. It has been shown that at high enough degree of coverage both designs give equivalent estimates of fish abundance and similar fish distribution, however at lower coverage the parallel transects are preferable. With increasing degree of coverage the fish abundance increases as well until some asymptotic value, which is reached at degree of coverage equal to 0.8. The three different methods of estimating total stock have been applied: arithmetic mean, weighted mean, and kriging. The estimates of fish abundance received by the first two methods were very similar, while the third one was significantly lower.