大西洋金枪鱼渔业平均营养级的长期变动

Long-term changes in the mean trophic level of tuna fishery in the Atlantic Ocean

利用国际养护大西洋金枪鱼委员会（ICCAT）提供的数据，结合Fishbase所提供的相关鱼种的营养级，该文分析了1950～2007年期间大西洋金枪鱼渔业的平均营养级（TLi）变动情况。结果表明，大西洋金枪鱼渔业TLi明显可分为三个阶段：1950～1961年，TLi呈明显的下降趋势，即TLi与年份呈现明显的负相关；1962～1992年，大部分TLi（75%）处于营养级平均水平（4.21）之下；1993～2007年，TLi均高于营养级平均水平（4.21）。1950～1960年，金枪鱼渔业产量与TLi之间呈明显的负相关，随着渔业产量的增加，TLi呈下降趋势；1961～1980年，金枪鱼渔业产量与TLi之间呈负相关，但趋势不明显；1981～1990年及1990年代以后，TLi并没有明显地变化趋势。1994年以前，FiB指数呈现明显的增长趋势；1994年以后，FiB指数出现明显的下降。

Based on the data provided by International Commission for the Conservation of Atlantic Tunas （ICCAT） and integrated with related information on trophic level of selected fish species collected from Fishbase, this paper analyzed the fluctuation on mean trophic level （TLi） of tuna fishery in the Atlantic Ocean from 1950 to 2007. The results indicated that three stages could be observed in the TLi of tuna fishery in the Atlantic Ocean, i.e., TLi had a significant decreasing trend and an inverse correlation to year from 1950 to 1961; there was a significant threshold. Most TLi （75%） was lower than average TLi （4.21） from 1962 to 1992, and TLi was higher than average TLi （4.21） after 1993. A negative correlation could be observed between annual catch of tuna fishery and TLi from 1950 to 1960, from 1961 to 1970 and from 1971 to 1980. There was no significant trend between annual catch of tuna fishery and TLi from 1981 to 1990 and after 1991. Two stages could be observed in the FiB index of tuna fishery in the Atlantic Ocean, i.e., FiB index had a significant increasing trend before 1994 and a remarkable decreasing trend after 1994.