捕捞对北部湾海洋生态系统的影响

Effects of fishing on the marine ecosystem of Beibu Gulf

利用Ecopath with Ecosim(EwE)5.1软件构建了北部湾海洋生态系统1959-1960年的Ecosim模型,包含渔业、海洋哺乳动物、海鸟、中上层鱼类、底层鱼类、底栖无脊椎动物等20个功能组,通过与1997-1999年调查数据对比,分析了捕捞活动对北部湾生态系统的结构和功能的影响.结果表明:近40年来在捕捞强度不断增加的压力下,生态系统的结构和功能发生显著变化,长寿命、高营养级的肉食性鱼类生物量下降明显,系统以短寿命、小型鱼类和无脊椎动物占优势.1999年的大中型鱼类的生物量仅为1960年的6%,而小型鱼类和无脊椎动物则明显上升,尤其是头足类生物量上升了2.7倍,渔获物的营养级则从1960年的3.2降低到1999年的2.98,体现了"捕捞降低海洋食物网"的特点,目前的开发模式是不可持续的.利用20世纪90年代数据预测了降低捕捞压力后生态系统的变化.本研究证实了可以使用Ecosim模型预测捕捞压力对生态系统的影响.

By using Ecopath with Ecosim 5.1 software,the Ecosim model of Beibu Gulf marine ecosystem in 1959-1960 was constructed,which included about 20 functional groups such as fishery,marine mammals,sea-birds,sharks,pelagic fishes,demersal fishes,and benthic crustaceans,etc.Through the comparison with the investigation data in 1997-1999,the effects of fishing on the structure and function of Beibu Gulf marine ecosystem were analyzed.The results indicated that with the increasing fishing pressure in past forty years,the ecosystem structure and function shifted drastically,with the biomass of long-lived,high trophic level and piscivorous fishes declined while short-lived and small fishes and benthic invertebrates dominated gradually.The biomass of piscivorous species in 1999 was only 6% of that in 1960,while cephalopods increased 2.7 times or more.The trophic level of the catch declined from 3.2 in 1960 to 2.98 in 1999,which fitted the rule of ＂fishing down the food web＂ and suggested that the present exploitation patterns were unsustainable.Based on the data of the 1990s,the changes of the ecosystem under decreasing fishing pressure were predicted.This study validated the feasibility of Ecosim model in predicting the effects of fishing pressure on marine ecosystem.