魚卵と仔魚の採集ネットへの網目保持

概要

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The present paper attempted to estimate the mesh retention of a plankton gauze, NIP #60 (0.33×0.36mm mesh width), widely used for eggs and larvae of fish in Japan. Catches by a gear with NIP #60 were compared with ones by another that retains larvae of Japanese anchovy Engraulis japonicus and gizzard shad Konosirus punctatus of all sizes. The obtained results in-dicated that 29% of japanese anchovy pre-larvae and 41% of gizzard shad pre-larvae were retained. Moreover, A some post-larvae of japanese anchovy less than 5.5mm long evidently passed through the mesh. However, few if any anchovy eggs were extruded through the mesh. While a theoretical consideration supports the hypothetical “diagonal rule” for slowly towed nets with some synthetic gauzes like NIP #60, the results do not agree with the “rule”. It is con-cluded that wide variations in mesh sizes on NIP #60 caused this conflict. The maximum cross-sectional diameter of an organism must be greater than the maximum mesh diagonal on NIP #60 if it is to be retained.
日本水産學會の論文