南太平洋延绳钓长鳍金枪鱼生物学组成及其与栖息环境关系

Relationship between biological composition and habitat characteristic of Thunnus alalunga of Chinese longline fishery in the South Pacific

长鳍金枪鱼（Thunnus alalunga）经济价值高,是我国延绳钓渔业重要的目标鱼种。根据2013年9月~2014年1月和2014年4~8月我国金枪鱼观察员在南太平洋东部海域收集的长鳍金枪鱼样本和海洋环境数据,对其生物学组成和栖息环境进行了研究。结果表明：叉长（FL,cm）与体质量（WW,kg）的关系为：WW=3×10-5×FL2.909 9（雌雄性,R2=0.915 3）;体长（TL,cm）与叉长（FL,cm）关系为：TL=1.033 6FL＋2.555（R2=0.961 4）;叉长（FL,cm）与两背鳍间距（LD1D2,cm）的关系为：LD1D2=0.248 5FL＋1.238 1（R2=0.815 1）;利用各水层长鳍金枪鱼渔获率（catch per unit effort,CPUE）推测其主要的栖息水层为150~270 m,栖息水层温度范围16~22℃,盐度范围35.0~35.6,其中最高资源丰度主要分布在190~230 m的水层,对应的温度为18~20℃,盐度为35.2~35.4。研究结果可为掌握南太平洋长鳍金枪鱼栖息环境提供基础数据。

Albacore tuna（ Thunnus alalunga） is an important upper tropic-level oceanic predator with a circum-global distribution between approximately 50° N and 40° S,although their abundance is relatively low in equatorial areas. It is an important target species with high economic value in Chinese tuna longline fishery,and it has a long history of scientific research. However,studies on biological composition,vertical distribution and habitat environment of albacore are rare in China. To better understand the drivers behind variability in catches of albacore tuna and links with prey densities and oceanographic conditions,there is a need to determine both the biological composition and movement patterns of albacore tuna. In this study,the focus is on analyzing the individual biology and habitat characteristic of albacore tuna based on data collected from Chinese tuna longline fishing-vessels in the South Pacific from September,2013 to January,2014 and from April to August,2014. The data contained catch species,biological parameters,fishing gear information and oceanographic conditions. The operating area ranged from 14° S to 22° S,and from 132° W to 105° W,near the sea of French Polynesia Islands. There were 136 sets altogether in these waters. Results showed that：the relationship between fork length（ FL,cm） and body weight（ WW,kg） can be expressed as： WW= 3 ×10- 5× FL2. 909 9（ male and female,R2= 0. 915 3）,and the relationship between fork length（ FL,cm） and body total length（ TL,cm） was： TL = 1. 033 6FL ＋ 2. 555（ R2= 0. 961 4）,while the two dorsal fins length（ LD1D2,cm） and fork length（ FL,cm） was： LD1D2= 0. 248 5FL ＋ 1. 238 1（ R2= 0. 815 1）. We used the CPUE（ catch per unit effort,CPUE） of different water depths to analyze the vertical distribution of albacore tuna,which may be affected by thermal conditions and salinity. It moved between 150 m and 270 m in depth,the temperature value ranged from 16 ℃ to 22 ℃,salinity from 35. 0 to 35. 6,and the stock appeared most between 190 m and 230 m in depth,18 ℃ to 20 ℃ in temperature and 35. 2 to 35. 4 in salinity. Longline fisheries of albacore tuna in the Pacific capture are year-round,although there are strong seasonal trends in catch distributions,with fisheries operating in southern latitudes（ south of 35° S） during late summer and autumn,and moving northwards during winter. The results could provide a basis for the South Pacific albacore tuna habitat,and for fishing vessels,it should set fishing gears legitimately,operate in suitable seasons and waters. Thus it could improve catch rate of target species and reduce bycatch rate to maintain the marine ecosystem balance.