New Device of the High Speed Surface Larva Net with the Result of Test Operation

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  • 高速表層用稚魚網の試作と曳網試験結果
  • コウソク ヒョウソウヨウ チギョモウ ノ シサク ト ヒキアミ シケン ケッカ

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Abstract

1) A New type of a surface larva net (Fig.1) was devised and constructed, that could be towed at a rather high speed (3-4 knots) in pararell line with the run of a ship and could also be kept within observable range throughout the operation from the bridge of the of the ship. 2) A stainless steel frame (Fig.2) keeping the mouth of the net open was designed and was equipped with a pair of otter boards, a depresser and a float, in order to keep the net in operation just beneath a water surface without any influence of the bow wave of ship. A net (Fig.3) was made of minnow net of nylon webbing and was installed to the frame. 3) Test operations of the net at seas (Fig. 4, 5, Table. 1) revealed that it could work as predicted, at least within towing speeds of 3 to 4 knots and that fish larvae collected by towing at a speed of 4 knots for 20 minutes showed significantly reduced injury when the codend with a closed end PVC adaptor (Fig. 3-b).

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