| 英文摘要 |
Fishery data of Taiwanese distant-water tuna longline fishery for swordfish in the North Pacific Ocean for 1968-2013, and for sailfish and spearfish in the Atlantic Ocean for 2002-2013 (observer data) and 2009-2013 (logbook data) were obtained from OFDC and used in this study. Generalized linear models were used to standardize swordfish CPUE (catch per unit effort) for the WCNPO and EPO stocks of swordfish in the North Pacific Ocean. Results show that factors considered in the models including Year, Quarter, Fishing Area, and two-way interactions were significant (P ＜ 0.01). Standardized swordfish CPUE were relatively stable before 1999 but varied slightly, with a clearly increasing trend after 2000. For the WCNPO stock, the CPUE trend increased during 2000-2005 and stabilized between 2006 and 2013, while for the EPO stock, the standardized CPUE decreased slightly during 2001 to 2005, but have been increasing since 2005. Stock assessment results based on age-structured models showed that the North Pacific swordfish was in a healthy status and relatively stable. Spawning stock biomass of WCNPO swordfish stock relative to MSY level S2012/SMSY was at 1.24, and fishing mortality to that at MSY level F2012/FMSY was at 0.68. For the EPO stock, spawning stock biomass of swordfish relative to MSY level S2012/SMSY was at 1.62, while fishing mortality to that at MSY level F2012/FMSY was at 0.20. Observer and logbook data for the distant-water tuna longline fishery in the Atlantic Ocean were analyzed in this study. Results showed that catch ratios of sailfish to spearfish were consistent based on logbooks and observer data. Annual ratios of catch a sailfish were higher (c.a. 0.79) in the eastern Atlantic Ocean, compared to that in the western Atlantic Ocean (~0.60), with a visible variation among years. Most sailfish were caught in tropical waters of the eastern Atlantic Ocean based on the analysis of catch distribution, while spearfish were mainly in pelagic waters in the North and South Atlantic Ocean. This is consistent with the results from the distribution of catch ratios of sailfish to spearfish. Sailfish were caught in tropical eastern Atlantic Ocean with a high catch ratio to spearfish (＞ 0.80), but this ration was lower (＜ 0.50) outside tropical waters of the western Atlantic Ocean (between 5°N and 20°S). Standardized CPUE of sailfish for the Taiwanese distant-water tuna longline fishing in the Atlantic Ocean were relatively stable with a slightly increasing trend. The CPUE for the eastern Atlantic stock increased substantially in 2012, but slightly decreased in 2013 for both stocks based on the preliminary data. It is therefore suggested to monitor the CPUE trends of both stocks closely. |
