Distribution of juvenile skipjack Katsuwonus pelamis and Tuna Thunnus spp. based on a midwater trawl net survey off Palau and Micronesia
1998
Tanabe, T. (Tohoku National Fisheries Research Inst., Shiogama, Miyagi (Japan)) | Ogura, M. | Takahashi, M. | Watanabe, Y.
A survey on juvenile skipjack Katsuwanus pelamis and other tuna Thunnus spp. was conducted suing a midwater trawl net in offshore areas off Palau and Micronesia, tropical western Pacific. 8097 juvenile skipjack and other tuna species were collected from October to December, 1992-1996 were analyzed. Juvenile skipjack were widely distributed in the area from the north equatorial current to the north equatorial counter current. Juvenile tuna were abundant in the area of the north equatorial counter current. These results suggest that the offshore area of Palau and Micronesia are important of juvenile skipjack and other tuna species as a nursery ground in the early life stages. The vertical distribution between skipjack and other tuna species were different. Juvenile skipjack were abundant from the lower portion of the mixed layer to the upper portion of the thermocline. While juvenile tuna were abundant in the mixed layer. These results indicate the optimal temperature for juvenile tuna is higher than that for skipjack. Furthermore, the appearance of skipjack and other tuna was restricted vertically with growth from juvenile to young. We consider that skipjack and other tuna species from juvenile to young select optimal oceanographic layers with the development of their swimming ability
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