Yokohama-shi, Japan
Yokohama-shi, Japan

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Kurosaka K.,Fisheries Research Agency FRA | Kurosaka K.,Tokyo University of Marine Science and Technology | Ochi Y.,Fisheries Research Agency FRA | Inada H.,Tokyo University of Marine Science and Technology | And 2 more authors.
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2013

In the jigging fishery for neon flying squid Ommastrephes bartramii, the catch loss due to hooked squid falling off caused by tentacle breakage should be reduced. For this purpose, the jig motion was monitored with an acceleration data logger to examine the upward jig speed for the squid to be hooked by tentacles or other arms. Only the ratio of hooked tentacles increased when the upward jig speed was faster than 1.75 m/s, which caused tentacle breakage for smaller squid (mantle length: ML < 35 cm). Through experimental fishing operation with different hauling speeds of the jig line drum, we concluded that the CPUE (number of squid caught/hour /jigging machine) can be maximized by controlling the upward jig speed at around 2.0 m/s for squid larger than 35 cm in ML, and at around 1.5 m/s for smaller squid, to reduce falling-off caused by tentacle breakage.

Kidokoro H.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Goto T.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Nagasawa T.,Fisheries Research Agency FRA | Nishida H.,Japan National Research Institute of Fisheries Science | And 2 more authors.
ICES Journal of Marine Science | Year: 2010

Following a climate regime shift (RS) in 1989 in the northwest Pacific and Sea of Japan, the main spawning grounds of the Japanese common squid (Todarodes pacificus) shifted from inshore areas off Honshu Island to the Tsushima Strait, and the stock size increased. Migration patterns of T. pacificus occurred after the RS, based on tagging experiments conducted in July to September of 1984 and 1987-1991, are examined using monthly shifts in average latitude of recapture sites every 10 d. Before the RS, recaptures were in the central Sea of Japan and in inshore areas off Honshu Island, but after the RS, there were no recaptures inshore off Honshu Island. The average latitude of the recapture sites in September was about 36-37°N before the RS and north of 40°N (near the release sites) after the RS. It is likely that the location of the spawning grounds has changed. © 2010 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved.

Kurosaka K.,Tokyo University of Marine Science and Technology | Kurosaka K.,Fisheries Research Agency FRA | Yamashita H.,Fisheries Research Agency FRA | Ogawa M.,Fisheries Research Agency FRA | And 2 more authors.
Fisheries Research | Year: 2012

In squid jigging operations for neon flying squid (Ommastrephes bartramii), 30-40% of hooked squid are estimated to fall off (i.e., become detached) from the jigs during the drum-hauling process, caused by breakage/severance of the hooked tentacle(s). Reducing fall-off events can lead to higher productivity and more efficient use of the squid resource. In the present study, there were 950 fall-off events either directly observed or assessed from the residue of tentacle(s) left on the jigs compared with the 1720 total captures, which comprises 35.6% of 2670 total hooked squids. The fall-off ratio according to the mantle length (ML) was examined using logistic curve analysis and a higher fall-off ratio for smaller squid was confirmed through size selectivity curve analysis. F 50, the 50% probability of fall off from the jig, was estimated to be 37.4cm ML. The breaking strength of a single tentacle was determined to be similar to the body weight (BW) of squid smaller than 41.4cm ML, indicating a high possibility of tentacle breakage in the case of 1 tentacle grabbing the jig for smaller-sized squid. © 2012 Elsevier B.V.

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