Using multi-sensor satellite remote sensing and catch data to detect ocean hot spots for albacore (Thunnus alalunga) in the northwestern North Pacific

摘要

To understand better and describe oceanic hot spots for albacore (Thunnus alalunga), we linked remotely sensed data from multi-sensor satellite images of TRMM/TMI sea-surface temperature (SST), SeaWiFS chlorophyll-a concentration and photosynthetically active radiation (PAR), and AVISO mean sea-level anomaly (MSLA) with fisheries catch data from 1998 to 2003. A probability map was generated based on biophysical environmental variables (SST and chlorophyll-a) in relation to the catch data. The probability of environmental variables was combined with an eddy kinetic energy (EKE) map to describe the oceanographic features around fishing locations. Primary production was examined to assess the productivity of the fishing grounds and was calculated from chlorophyll-a, SST and PAR using the vertically generalized production model (VGPM). Results indicate that the greatest catches occurred mainly in November, and the catches were highest at warm SSTs (19.78 ± 1.69℃) and relatively high chlorophyll-a concentrations (0.31 ± 0.13mgm~(-3)). Highest catches occurred in areas where primary production rates ranged from 15.65 to 20.61 g Cm~(-2) month~(-1) (18.12 ± 4.98 g Cm~(-2)month~(-1)). Our analysis found that catch per unit efforts (CPUEs) tended to increase significantly in areas of increasing probability of environmental variables (P < 0.0001) during the season of high abundance. Albacore CPUEs were clearly higher during November 1998-2000 than during November 2002-2003. During 1998-2000, the congregating spots of albacore clearly showed that the probability and primary productivity rates were higher than during 2002-2003. It is likely that the area of high probability (preferred biophysical environmental factors) corresponds to the location of frontal zones, where albacore prey were abundant. Regions of high tuna abundance occurred in relatively high EKE and geostrophic currents, reflecting that tuna aggregations were associated with anticyclonic eddies. These eddies may trap and then concentrate albacore prey transported by the Kuroshio Extension and the Oyashio intrusion near the Shatsky Rise area, hence producing productive tuna fishing grounds. The eddy fields were areas of high catch probability. These findings suggest that the ocean hot spots for albacore are linked to hydrographic features, frontal zones and eddy fields, which influence distribution pattern and formation of tuna abundance. Our analysis provide an illustration on how multi-sensor satellite remote sensing can aid in detecting and visualizing pelagic hot spots. These results can lead to improved habitat protection and tuna fishery management.