根据中国渔业统计年鉴19562014年中国北方三省一市(河北省、辽宁省、山东省和天津市)的捕捞量统计资料,综合分析了黄、渤海海域38种主要渔获种类的平均营养级、渔获量及渔获组成的长期变化情况,并结合FIB指数(Fishing in Balance Index),深入探讨黄、渤海渔业状况的年间变化。研究表明,19562014年黄、渤海渔获物平均营养级在3.63~4.46的范围内波动,整体呈下降趋势。大致可分为4个阶段:(1)19561969年,平均营养级整体呈下降趋势,在1957年达到历史最高点4.46,1969年下降到3.83;(2)19701975年,整体呈上升趋势,在1975年上升到第三个高峰值4.32;(3)19761997年,整体呈下降趋势,平均营养级在波动中逐渐下降,1992年达到历史最低点3.63;(4)19982014年,整体有小幅度上升,最终稳定在3.83左右。FIB指数整体呈先下降后上升的趋势。19561968年,FIB指数经过一个振荡后逐渐下降到最低点-1.57;19692006年,FIB指数整体在波动中逐渐上升至最高点1.78;20072014年,FIB指数下降后趋于稳定。渔获量的长期变化显示,近几十年间黄、渤海高营养级和中低营养级种类的渔获量均呈上升趋势,但高营养级种类所占比例下降,中低营养级种类所占比例上升。与全球及其它海域相比,黄、渤海渔获物平均营养级的下降幅度和下降速率均高于全球平均水平和葡萄牙海域,但低于南澳大利亚和东海海域。
英文摘要:
Fluctuations in the mean trophic level for marine catches can reflect dynamic variation in fish community structure,which are important for understanding of marine ecosystem structure and variations. According to statistical data from the Chinese Fisheries Statistics Yearbook during 1956-2014,we analyzed long-term trends in the mean trophic level(MTL),marine catches and catch compositions for 38 major marine species in the Yellow Sea and Bohai Sea,and also calculated the Fishing in Balance Index(FIB)to examine the interannual variations of fishery resources in the Yellow Sea and Bohai Sea. Results showed that the MTL of catches in the Yellow Sea and Bohai Sea fluctuated between 3.63 and 4.46 during 1956-2014,and showed a downward trend.The long-term trends in MTL of catches could be divided into four stages:(1)From 1956 to 1969,MTL showed a declined trend,which reached the maximum value of 4.46 in 1957 and then decreased to 3.83 in 1969;(2)From 1970 to 1975,MTL showed a rising trend and reached the third maximum value of 4.32 in 1975;(3)From 1976 to 1997, MTL showed a declined trend,which decreased slowly to the minimum value in 1992;(4)From 1998 to 2014,MTL increased a little and then remained at about 3.83.The FIB index decreased firstly and then increased.From 1956 to 1968,the FIB index decreased to the minimum value of-1.57 through a sharp fluctuation because the exploitation of the Yellow Sea and Bohai Sea was still in the early stage.From 1969 to 2006,the FIB index increased gradually and then reached the maximum value of 1.78,because the scope and strength of exploitation in the Yellow Sea and Bohai Sea was increasing.From 2007 to 2014,the FIB index decreased and then remained stable,which might be related to the impairment of the ecosystem in the Yellow Sea and Bohai Sea.Long-term variations of marine fisheries suggested that catches of high trophic level species,middle trophic level species and low trophic level species were both increasing in the Yellow Sea and Bohai Sea during recent decades.However,the proportion of high trophic level species went down and the proportion of middle trophic level species and low trophic level species increased,which indicated that MTL of catches in the Yellow Sea and Bohai Sea showed aFishing through marine food websphenomenon.This meant that although the marine catches were still at a high level,the proportion of fishes in medium and lower trophic level and invertebrates increased a lot so the quality of catches deteriorated.Compared with other areas,the extent and rate of declining of MTL in the Yellow Sea and Bohai Sea exceeded the Portuguese Sea and the global average level,but were inferior to that in the South Australian Sea and the East China Sea.Moreover,changes in mean body size,climate and market price can also have an influence on long term variations in the mean trophic level,so more factors should be considered in the future.In conclusion,the marine catches have exceeded what it can afford in the Yellow Sea and Bohai Sea,so we should strengthen the management and protect of fishery resources in order to promote the sustainable development of fishery in the Yellow Sea and Bohai Sea.