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General Session 3: Biological oceanography & global change |
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Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean
GS3-23
Kuowei Lan* , Department of Environmental Biology and Fisheries Science, National Taiwan Ocean University, 2 Pei-Ning Rd., Keelung 20224, Taiwan, R.O.C.
Chin-Pei Chou, Department of Environmental Biology and Fisheries Science, National Taiwan Ocean University, 2 Pei-Ning Rd., Keelung 20224, Taiwan, R.O.C.
Ming-An Lee, Department of Environmental Biology and Fisheries Science, National Taiwan Ocean University, 2 Pei-Ning Rd., Keelung 20224, Taiwan, R.O.C.
Ali Haghi Vayghan, Department of Fisheries, Faculty of Fisheries and Environment, Gorgan University of Agricultural Science and Natural Resources, Gorgan, Iran
Presenter Email: kwlan@mail.ntou.edu.tw
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| The environmental processes associated with variability in the catch rates of bigeye tuna are largely unexplored in the Atlantic Ocean. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1981 to 2009 and investigated the association between environmental variables and catch rates to understand the processes influencing the bigeye tuna distribution in the Atlantic Ocean. The results revealed that the catch rates and distribution of bigeye tuna were related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 63.3% of the cumulative deviance in the entire Atlantic Ocean. Furthermore, temporal and spatial factors accounted for considerable variations in the tropical Indian Ocean and indicated that the first and second quarters are the major fishing seasons and that the catch rates increased from 1985 to 1995. In addition, the catch rates of albacore had a significant correlation with the catch rates of bigeye tuna. Environmental factors, the sea surface temperature (SST) and depth of the 20-degree isotherm, substantially contributed to the explained deviance. The potential fishing grounds with SSTs of 22–28°C and a D20 shallower than 150 m were concentrated in the central and eastern Atlantic Ocean during the negative tropical northern Atlantic (TNA) and positive North Atlantic Oscillation events. The potential fishing grounds increased in size and extended to the western Atlantic Ocean in the positive TNA events, especially in the major the fishing season. Moreover, decadal-scale variability was observed for bigeye tuna with significant shifts occurring in approximately 1995, which were in accordance with that in the TNA. |
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