Multispecies ecological models have been used for predicting the effects of fishing activity and evaluating the performance of management strategies. Size-spectrum models are one type of physiologically-structured eco...Multispecies ecological models have been used for predicting the effects of fishing activity and evaluating the performance of management strategies. Size-spectrum models are one type of physiologically-structured ecological model that provide a feasible approach to describing fish communities in terms of individual dietary variation and ontogenetic niche shift. Despite the potential of ecological models in improving our understanding of ecosystems, their application is usually limited for data-poor fisheries. As a first step in implementing ecosystem-based fisheries management（EBFM）, this study built a size-spectrum model for the fish community in the Haizhou Bay, China. We describe data collection procedures and model parameterization to facilitate the implementation of such size-spectrum models for future studies of data-poor ecosystems. The effects of fishing on the ecosystem were exemplified with a range of fishing effort and were monitored with a set of ecological indicators. Total community biomass, biodiversity index, W-statistic, LFI（Large fish index）, Mean W（mean body weight） and Slope（slope of community size spectra） showed a strong non-linear pattern in response to fishing pressure, and largest fishing effort did not generate the most drastic responses in certain scenarios. We emphasize the value and feasibility of developing size-spectrum models to capture ecological dynamics and suggest limitations as well as potential for model improvement. This study aims to promote a wide use of this type of model in support of EBFM.展开更多
The size-spectrum model has been considered a useful tool for understanding the structures of marine ecosystems and examining management implications for fisheries.Based on Chinese tuna longline observer data from the...The size-spectrum model has been considered a useful tool for understanding the structures of marine ecosystems and examining management implications for fisheries.Based on Chinese tuna longline observer data from the central and eastern tropical Pacific Ocean and published data,we developed and calibrated a multispecies size-spectrum model of twenty common and commercially important species in this area.We then use the model to project the status of the species from 2016 to 2050 under five constant-fishing-mortality management scenarios:(1)F=0;(2)F=F_(recent),the average fishing mortality from 2013 to 2015;(3)F=0.5F_(recent);(4)F=2F_(recent) and(5)F=3F_(recent).Several ecological indicators were used to track the dynamics of the community structure under different levels of fishing,including the mean body weight,slope of community size spectra(Slope),and total biomass.The validation demonstrated that size-at-age data of nine main catch species between our model predictions and those empirical data from assessments by the Western and Central Pacific Fisheries Commission matched well,with the R^(2)>0.9.The direct effect of fishing was the decreasing abundance of large-sized individuals.The mean body weight in the community decreased by~1500 g(21%)by 2050 when F doubled from F_(recent) to 2F_(recent).The higher the fishing mortality,the steeper the Slope was.The projection also indicated that fishing impacts reflected by the total biomass did not increase proportionally with the increasing fishing mortality.The biomass of the main target tuna species was still abundant over the projection period under the recent fishing mortality,except Albacore tuna(Thunnus alalunga).For sharks and billfishes,their biomass remained at relatively higher levels only under the F=0 scenario.The results can serve as a scientific reference for alternative management strategies in the tropical Pacific Ocean.展开更多
为了实现致密岩心的孔隙量化表征,采用核磁共振(nuclear magnetic resonance,NMR)技术,利用T2弛豫时间和孔隙半径(r)的正比关系可测致密岩心的孔隙度、渗透率和孔径分布,利用核磁共振T2截止值可区分孔隙中的自由流体和束缚流体。从核磁...为了实现致密岩心的孔隙量化表征,采用核磁共振(nuclear magnetic resonance,NMR)技术,利用T2弛豫时间和孔隙半径(r)的正比关系可测致密岩心的孔隙度、渗透率和孔径分布,利用核磁共振T2截止值可区分孔隙中的自由流体和束缚流体。从核磁共振表征岩心孔隙的原理出发,分析了核磁共振T2谱与岩心孔隙度、渗透率、孔径分布、孔隙内可动流体的关系。根据上述原理,通过实例验证了核磁共振技术在致密岩心孔隙度和渗透率量化表征中的准确性和适用性。实验岩心的T2截止值和孔径分布测试表明:1号岩心T2截止值为21.85 ms,2号岩心的T2截止值为40.11 ms;1号岩心小孔隙分量大,2号岩心孔隙分布较均匀。截止值的计算结果表明地区经验法得出的T2截止值不完全适用于该区域的致密岩心,有必要建立区域性的截止值变化范围图版。展开更多
基金The Special Fund for Agriscientific Research in the Public Interest under contract No.201303050the Fundamental Research Funds for the Central Universities under contract Nos 201022001 and 201262004
文摘Multispecies ecological models have been used for predicting the effects of fishing activity and evaluating the performance of management strategies. Size-spectrum models are one type of physiologically-structured ecological model that provide a feasible approach to describing fish communities in terms of individual dietary variation and ontogenetic niche shift. Despite the potential of ecological models in improving our understanding of ecosystems, their application is usually limited for data-poor fisheries. As a first step in implementing ecosystem-based fisheries management（EBFM）, this study built a size-spectrum model for the fish community in the Haizhou Bay, China. We describe data collection procedures and model parameterization to facilitate the implementation of such size-spectrum models for future studies of data-poor ecosystems. The effects of fishing on the ecosystem were exemplified with a range of fishing effort and were monitored with a set of ecological indicators. Total community biomass, biodiversity index, W-statistic, LFI（Large fish index）, Mean W（mean body weight） and Slope（slope of community size spectra） showed a strong non-linear pattern in response to fishing pressure, and largest fishing effort did not generate the most drastic responses in certain scenarios. We emphasize the value and feasibility of developing size-spectrum models to capture ecological dynamics and suggest limitations as well as potential for model improvement. This study aims to promote a wide use of this type of model in support of EBFM.
基金The National Natural Science Foundation of China under contract No.41676120。
文摘The size-spectrum model has been considered a useful tool for understanding the structures of marine ecosystems and examining management implications for fisheries.Based on Chinese tuna longline observer data from the central and eastern tropical Pacific Ocean and published data,we developed and calibrated a multispecies size-spectrum model of twenty common and commercially important species in this area.We then use the model to project the status of the species from 2016 to 2050 under five constant-fishing-mortality management scenarios:(1)F=0;(2)F=F_(recent),the average fishing mortality from 2013 to 2015;(3)F=0.5F_(recent);(4)F=2F_(recent) and(5)F=3F_(recent).Several ecological indicators were used to track the dynamics of the community structure under different levels of fishing,including the mean body weight,slope of community size spectra(Slope),and total biomass.The validation demonstrated that size-at-age data of nine main catch species between our model predictions and those empirical data from assessments by the Western and Central Pacific Fisheries Commission matched well,with the R^(2)>0.9.The direct effect of fishing was the decreasing abundance of large-sized individuals.The mean body weight in the community decreased by~1500 g(21%)by 2050 when F doubled from F_(recent) to 2F_(recent).The higher the fishing mortality,the steeper the Slope was.The projection also indicated that fishing impacts reflected by the total biomass did not increase proportionally with the increasing fishing mortality.The biomass of the main target tuna species was still abundant over the projection period under the recent fishing mortality,except Albacore tuna(Thunnus alalunga).For sharks and billfishes,their biomass remained at relatively higher levels only under the F=0 scenario.The results can serve as a scientific reference for alternative management strategies in the tropical Pacific Ocean.
文摘为了实现致密岩心的孔隙量化表征,采用核磁共振(nuclear magnetic resonance,NMR)技术,利用T2弛豫时间和孔隙半径(r)的正比关系可测致密岩心的孔隙度、渗透率和孔径分布,利用核磁共振T2截止值可区分孔隙中的自由流体和束缚流体。从核磁共振表征岩心孔隙的原理出发,分析了核磁共振T2谱与岩心孔隙度、渗透率、孔径分布、孔隙内可动流体的关系。根据上述原理,通过实例验证了核磁共振技术在致密岩心孔隙度和渗透率量化表征中的准确性和适用性。实验岩心的T2截止值和孔径分布测试表明:1号岩心T2截止值为21.85 ms,2号岩心的T2截止值为40.11 ms;1号岩心小孔隙分量大,2号岩心孔隙分布较均匀。截止值的计算结果表明地区经验法得出的T2截止值不完全适用于该区域的致密岩心,有必要建立区域性的截止值变化范围图版。
