| 英文摘要 |
For swordfish in the Indian Ocean, the results of this study indicated that the current (2007) spawning biomass was about 70% of initial level and was about triple of MSY level. Based on various assumptions, the most optimistic assessment would be obtained when separating the CPUEs of Japanese longline fleets into two time periods and the most pessimistic assessment would be obtained when assuming that the selectivities for all of longline fleets are logistic curves. Even for the most pessimistic results, however, the fishery exploitation was close to MSY level but did not exceed the MSY level.??
??? For swordfish in the Atlantic Ocean, there is no obvious trend for historical catch-at-size. In recent years, the mean catch-at-sizes of swordfish in the northern and southern Atlantic Ocean were obviously larger than those in previous years. The CPUEs of the swordfish in the northern Atlantic Ocean were relative stable before 1990s, and substantially increased in the mid 1990s, and gradually decreased after 1995. The CPUE trend of the swordfish in the southern Atlantic Ocean was similar to that in the northern Atlantic Ocean, but it was relatively stable after 2000.
??? For southern bluefin tuna, the CPUEs obviously decreased in 2002, remained stable for two years, increased in 2006, and were stable thereafter. There was no obvious CPUE trend for fish older than 10 years. The CPUEs for fish of ages 6-9 increased in 2006-2008. However, the CPUEs for young fish obviously increased in 2006-2008, especially for the fish of age 3-5 years and their CPUEs were about triple of those before 2006. |