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|Title: ||Estimation of the Abundance Index (AI) of swordfish (Xiphias gladius) in the Indian Ocean (IO) based on the fine scale catch and effort data of the Japanese tuna longline fisheries (1980-2010)|
|Authors: ||Tom Nishida;Toshihide Kitakado;Sheng-Ping Wang|
|Issue Date: ||2012-11-20T01:28:53Z
|Publisher: ||The ninth session of the IOTC Working Party on Billfish (WPB), Indian Ocean Tuna Commission (IOTC), July 4-8, 2011. Victoria, Seychelles|
|Abstract: ||abstract:We attempted to standardize Japanese longline swordfish nominal CPUE based on the fine scale catch and effort data (set by set). Results suggested that the abundance index (AI) were high level in 1980 to 1997 and decreased rapidly to 2005 then increased sharply to 2010 and recovered to the lower range of the previous high level (1980-1997). At the initial analyses we used anomalies of ENV data as suggested by Kolody (2010) and Nishida (2010). However all ENV data are not sensitive at all (non significant) in the GLM analyses. Thus we re-used the original ENV data as in the past then we found that the a few ENV (moon phase, thermocline depth and temperature gradient at 45m depth) suggested significant effects. This demonstrates effectiveness and importance of some environmental data in the GLM. In addition it was also resulted that V (vessel) affected nominal CPUE which implied that there were different levels of catchability among vessels due to the skipper’s skills. From STD CPUE by region we observed good recovery trends in recent years in the southern IO (SW and SE regions), while the steady trends in Northern IO (NE and NW). These recoveries are probably due to much less fishing pressure in recent 3-4 years than before because of the pirate problems in the large part of the western Indian Ocean.|
|Appears in Collections:||[環境生物與漁業科學學系] 演講及研討會|
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