Journal of The School of Marine Science and Technology,Vol.7 No.1
An attempt to forecast favorable temperature zone for fishing ground formation of skipjack tuna Katsuwonus pelamis using satellite data and fishing ground data
Yuichiro HARA, Noboru KATO, Kedarnath MAHAPATRA and Yoshihiro OKADA
Abstract
The skipjack tuna Katsuwonus pelamis maintains adequate body temperature by searching actively for warm waters.Their congregation is associated with the oceanic thermal frontal systems due to high forage concentration in the frontal waters. Thus temporal variability of oceanic thermal fronts can be used to detect routes for their migration. The main objective of our study is to assess the feasibility of short-term forecast of the favorable temperature zone for skipjack tuna fishing ground. The relationship between short-term spatial variability of SST field and skipjack tuna fishing ground was investigated at two sampling sites off the eastern coast of Japan；Sanriku Area and Tokai Area during September 2001 and April-May 2005 respectively.Fishing locations and in situ SST data from the logbook of the fishing vessels (QRY data)recorded continuously over ten days were used to estimate SST field for the 11th day by applying multiple regression analysis taking SST (y)as the target parameter (dependent variable)and Julian day (x1), latitude (x2)and longitude (x3)as the independent variables. Satellite derived high resolution SST image from NOAA-AVHRR/MODIS of the target day was used to validate the estimated SST field.95％ and 74％ of the fishing locations of the target day were found to have occurred in the areas with SST difference of 1.0°C between the estimated SST and satellite derived SST in September 2001 and April-May 2005 respectively.In September 2001,QRY SST and estimated SST ranges were 18-20°C and 18-19°C respectively.Similarly,in April-May 2005,estimated SST range (20-21°C)was noticed to be narrower compared to that of QRY SST (19-23°C).We termed estimated SST as the “favorable temperature”because of its usefulness in locating skipjack tuna fishing ground.Our results indicated apparent shift in the fishing ground favorable SST ranges under diverse seasonal andoceanographic conditions.