Comparison of Two Mesh Sizes for Collecting Larval Yellow Perch in Surface Trawls

Abstract

We evaluated the differences in density estimates (larvae/100 m³), mean total lengths (TL; mm), and length frequency distributions of larval yellow perch Perca flavescens collected using 500- and 1,000-μm-mesh surface trawls in a small South Dakota lake. No significant difference in larval yellow perch density between mesh sizes was detected across sampling dates (F = 0.02, df = 1, P = 0.90). Significant differences in the length frequency distributions (Kolmogorov–Smirnov asymptotic test statistic = 1.532; df = 100, 106; P = 0.02) of larval yellow perch were detected on one early sampling date; however, when mean lengths exceeded 9 mm, total lengths and length frequency distributions were similar across mesh sizes. We collected smaller larval yellow perch (mean TL = 4.9 mm) earlier in the 500-μm-mesh net than in the 1,000-μm-mesh net. Peak larval yellow perch density was observed simultaneously and did not differ between mesh sizes. Estimates of precision associated with peak larval densities were also similar between meshes. Our findings indicate that in waters where a high abundance of plankton can inhibit the efficiency of larval surface trawling due to clogging, the use of a 1,000-μm-mesh net would provide results (in terms of larval yellow perch relative abundance and size characteristics) similar to those obtained when using a 500-μm-mesh net, while potentially minimizing required sample storage space and handling time.