渔获物平均营养级在渔业可持续性评价中的应用研究进展

高强度的捕捞努力量和渔业管理不力等因素导致全球范围内传统渔业资源的衰退,近年来渔获物平均营养级(MTL,mean trophic level)作为以生态系统为基础的渔业管理评价指标被普遍应用。本文在广泛收集国内外相关文献资料基础上,系统地介绍了MTL在渔业资源评价中的研究进展。已有研究显示,MTL能够利用已知渔获数据来分析,且参数化较为简便,在评价渔业可持续性中优势明显。受以渔获量作为生态系统指标、营养级(TL,trophic level)随体长的变化、渔获统计数据质量、低TL种类的过多捕捞和海域环境富营养化等因素的影响,在评估渔业资源利用状况时,需将MTL与剔除TL小于3.25物种下的3.25MTL、渔业均衡指数(FIB)等营养指标综合分析。此外,综合运用多指标,将营养指标与渔获组成、中上层鱼类与底层鱼类产量的比值、市场价格等指标结合分析,有助于掌握引起MTL变动的因素,更加全面地掌握捕捞活动下鱼类群落结构的实际变化状况。

Research progress in application of mean trophic level of catch in assessing fishery sustainability

Owing to the high levels of fishing efforts and ineffective fishery management,traditional fishery resources have been collapsing all over the world.As an ecosystem-based approach,the indicator of mean trophic level of fisheries catches (MTL)uses readily available data and is quick and easy to calculate.In addition,MTL is very sensitive to the dynamics of fish community.MTL has been widely used to assess the impact of fishing by many international bodies,including the Convention on Biological Diversity,European Union,and Caribbean Large Marine Ecosystem and Adjacent Project.The paper reviewed research progress of MTL as an indicator of fishery sustainability based on extensive collection of related literatures at home and abroad .Analysis showes that MTL is a promising tool to assess fishery sustainability,and there are at least two ways to lead a decreasing MTL trend.The first is through the sequential replacement of long-lived,high trophic level species with short-lived,low trophic level species as the former are depleted to economic extinction,it is termed"fishing down marine food webs";the second is through the sequential addition of low trophic level fisheries within an ecosystem,and it is called"fishing through marine food webs".Besides,the underlying ecological effects associated with different mechanisms showed significant differences,and different governance responses should be employed for each mechanism.Considering the factors of using landing data as ecosystem indicators,trophic level changing with body length,quality of fishery statistics data,harvesting too much low TL species and eutrophication,we should combine MTL with other trophic indicators such as cutMTL and FIB (Fishing-in-balance)index to provide a whole analysis.Furthermore,intergrating trophic indicators with other indexes such as catch composition,pelagic(P)to demersal(D)fish biomass ratio (P/D index)in fishery landings and market price will contribute to determining the cause of changing MTL,thus providing a comprehensive view of community structural changes under fishing activities.