Newly designed quantitative frame trawl for sampling larval and juvenile pelagic fish

Abstract

A newly designed frame trawl with a 5 m2 mouth area was constructed for quantitative sampling of larval and juvenile pelagic fishes and its performance was tested in the ocean. Towing depth of the trawl was easily controlled by adjusting the warp length, and the stability at depth increased with decreasing weight of the net in water. Larval and juvenile fishes were sampled using the trawl at stations in the Kuroshio-Oyashio transition region from 29 May to 24 June 1998. A total of 44 oblique tows were conducted and towing depths of the frame trawl had a high degree of stability despite the various sea conditions and the fluctuations in the ship speed. Larvae and juveniles of Japanese anchovy Engraulis japonicus and Myctophidae made up the majority of the specimens. It was concluded that the newly constructed trawl was appropriate for the quantitative sampling of pelagic fish larvae and juveniles.