Relative Efficiency of Two Trawls for Monitoring Juvenile Fish Abundance

Twenty-seven comparison tows were made between a 2-seam otter trawl with 6 loops of 13 link, 4.8-mm chain attached to the leadline (original net) and an identical trawl with additional chain loops attached every 25.4 cm across the entire leadline (heavily chained net) during June-August 1988 in tributaries of the Neuse River, N.C. Objectives were to determine the effect of the heavily chained net on the juvenile finfish, crab, and shrimp catch-per-unit-effort (CPUE) estimates and the feasibility of developing conversion factors to convert CPUE estimates from one net type to the other. The CPUE estimates were significantly higher (P ≤ 0.01) with the heavily chained net for juvenile Atlantic croaker (Micropogonias undulatus), southern flounder (Paralichthys lethostigma), and blue crab (Callinectes sapidus). Results of chi-square tests and comparison of length distribution patterns of harvested animals indicated that the original net was biased against smaller crabs and flounder and larger brown shrimp (Penaeus aztecus) and spot (Leiostomus xanthurus). Results of this comparison indicated that the heavily chained net was more effective for generating accurate indices of juvenile abundance for all species of interest.

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