Objective:To evaluate exploitation status of the stocks of demersal fishes in Omani artisanal fisheries.Methods:Time-series data between 2005 and 2014 on catches and effort represented by the number of fishing boats w...Objective:To evaluate exploitation status of the stocks of demersal fishes in Omani artisanal fisheries.Methods:Time-series data between 2005 and 2014 on catches and effort represented by the number of fishing boats were used to estimate catch per unit effort and maximum sustainable yields applying Schaefer surplus production model.Regression analyses were made online using GraphPad software.Results:The study revealed that increasing the number of boats on the fishery caused a decrease of catch per unit effort of some species.Maximum sustainable yields and exploitation status were estimated for these species applying.Conclusions:Some demersal fish species were found to be caught in quantities exceeding maximum sustainable yields during some fishing seasons indicating overexploitation of their stocks.展开更多
In order to develop a method that apply sampling survey data randomly obtained at fishing ports to fish stock assessments,based on fish landing surveys conducted at fishing ports in the northern South China Sea(SCS),1...In order to develop a method that apply sampling survey data randomly obtained at fishing ports to fish stock assessments,based on fish landing surveys conducted at fishing ports in the northern South China Sea(SCS),19 Threadfin porgy(Evynnis cardinalis)catch per unit effort(CPUE)datasets were collected for fishing vessels with different gear types and engine powers and incorporated into surplus production models.Considering only the fitting performance,the Schaefer model had the best overall goodness of fit,followed by the Fox,CYP,W-H,and Schnute models.Among fishing vessels with different gears and engine powers,the data were best fitted for single-trawl vessels powered by 301-400-kW engines and for gillnet vessels powered by>200-kW engines.Eight model expressions were superior and selected for subsequent analyses based on their goodness of fit and relative residuals.The Kobe plot analysis results showed an optimistic fish stock status when using the four model expressions,required more caution when using three model expressions and output pessimistic estimations using one model expression.Considering the incomplete information acquired,a compromising decision-making method was used to derive a 2017 northern SCS E.cardinalis total allowed catch(TAC)of 44,691.21 t.The different conclusions drawn from estimations using CPUEs reflect variable exploitation and utilization fish stock statuses among fishing vessels with different gears and engine powers.Hence,the fishing operations were grouped according to their CPUE relationship,and recommendations regarding optimum fishing efforts were assigned to the groups following a fundamental principle:to improve fishery TAC management,fishing efforts should be reduced if the fish stock assessment is pessimistic and maintained if the assessment is optimistic.This study providing a feasible technical method for the TAC management of China’s offshore fisheries.展开更多
为了解和掌握月相对渔业产量或单位捕捞努力量渔获量(catch per unit effort,CPUE)的影响规律,利用2016—2019年(每年3月2日—11月29日)马达加斯加西海岸底拖网独角新对虾(Metapenaeus monoceros)和2017—2020年(每年6月15日—10月9日)...为了解和掌握月相对渔业产量或单位捕捞努力量渔获量(catch per unit effort,CPUE)的影响规律,利用2016—2019年(每年3月2日—11月29日)马达加斯加西海岸底拖网独角新对虾(Metapenaeus monoceros)和2017—2020年(每年6月15日—10月9日)西白令海中层拖网狭鳕(Theragra chalcogramma)的渔业生产数据,结合基于圆形统计的广义线性模型(GLM)和基于时间序列的广义加性模型(GAM)2种不同的月相量化和统计的方法,分析月相对拖网渔业CPUE的影响。结果表明:月相对独角新对虾的CPUE具有显著性影响(P<0.05),2种方法得出的影响趋势较为一致,较高CPUE出现在上弦月;基于圆形统计的GLM显示,月相对狭鳕CPUE具有显著性影响(P<0.05),较高CPUE出现在新月期,而基于时间序列的GAM显示,月相对狭鳕CPUE的影响不显著(P>0.05);交叉验证显示,基于圆形统计的GLM平均绝对误差(E_(MA))和均方根误差(E_(RMS))均小于基于时间序列的GAM,而GLM分析的决定系数R~2则大于GAM,表明前者的拟合具有更好的准确性、稳定性和拟合优度。研究表明,当周期性循环变量(月份、月相和小时等)具有较弱的显著性时,使用基于圆形统计的GLM更能反映月相对拖网渔业CPUE的影响。展开更多
拦河筑坝所导致的物理阻隔和生态阻隔是影响鱼类迁徙的关键因素。圆口铜鱼Coreius guichenoti(Sauvage&Dabry de Thiersant,1874)作为长江上游重要的河流性洄游鱼类,其迁徙不可避免受到金沙江下游向家坝和溪洛渡大型水电站蓄水的影...拦河筑坝所导致的物理阻隔和生态阻隔是影响鱼类迁徙的关键因素。圆口铜鱼Coreius guichenoti(Sauvage&Dabry de Thiersant,1874)作为长江上游重要的河流性洄游鱼类,其迁徙不可避免受到金沙江下游向家坝和溪洛渡大型水电站蓄水的影响。关于向家坝和溪洛渡蓄水是否会显著阻隔圆口铜鱼个体的下行以及不同年龄个体之间受阻隔的影响是否存在差异,迄今为止,还未有相关报道。本文拟通过2012—2014年对长江上游永善江段和宜宾江段圆口铜鱼年龄结构变动的研究,探讨向家坝和溪洛渡蓄水对圆口铜鱼不同年龄个体下行阻隔的影响程度。结果表明:1)向家坝和溪洛渡蓄水对圆口铜鱼下行产生了明显的阻隔效应;2)向家坝和溪洛渡蓄水对1龄个体的下行阻隔最明显且最严重;3)与单一的大型水库和大坝相比,多个梯级的大型水库和大坝会对圆口铜鱼的下行产生更为严重的阻隔效应。本文拟为金沙江下游圆口铜鱼的资源保护提供基础数据支持。展开更多
Two fishing methods including gillnetting and trawling to estimate attributes of fish assemblage were compared in Dianshan Lake from August 2009 to July 2010. Species composition dif fered significantly between the ge...Two fishing methods including gillnetting and trawling to estimate attributes of fish assemblage were compared in Dianshan Lake from August 2009 to July 2010. Species composition dif fered significantly between the gears, with four significant contributors in gillnet catches and one in trawl catches. Trawling collected more proportions of benthic species by number and biomass than gillnetting. Size distribution was significantly influenced by fishing technique; gillnetting captured relatively less small-sized fishes and trawling captured less large-sized individuals. Trawling produced species richness closer to the one expected than gillnetting. On the whole, trawl catch was a quadratic polynomial function of gillnet catch and a significantly negative correlation was found between them, both of which varied as dif ferent polynomial functions of temperature. However, trawl and gillnet catches were significantly correlated only in one of five month groups. It is concluded that single-gear-based surveys can be misleading in assessments of attributes of fish assemblages, bottom trawling is a more ef fective gear for assessing fish diversity than benthic gillnetting, and using gillnet catches as an indicator of fish density depends on fishing season in the lake.展开更多
Delay-difference models are intermediate between simple surplus-production models and complicated age-structured models. Such intermediate models are more efficient and require less data than age-structured models. In...Delay-difference models are intermediate between simple surplus-production models and complicated age-structured models. Such intermediate models are more efficient and require less data than age-structured models. In this study, a delay-differ- ence model was applied to fit catch and catch per unit effort （CPUE） data （1975-2011） of the southern Atlantic albacore （Thunnus alalunga） stock. The proposed delay-difference model captures annual fluctuations in predicted CPUE data better than Fox model. In a Monte Carlo simulation, white noises （CVs） were superimposed on the observed CPUE data at four levels. Relative estimate error was then calculated to compare the estimated results with the true values of parameters a and fl in Ricker stock-recruitment model and the catchability coefficient q. a is more sensitive to CV than fl and q. We also calculated an 80% percentile confidence interval of the maximum sustainable yield （MSY, 21756 t to 23408 t; median 22490 t） with the delay-difference model. The yield of the southern Atlantic albacore stock in 2011 was 24122t, and the estimated ratios of catch against MSY for the past seven years were approxi- mately 1.0. We suggest that care should be taken to protect the albacore fishery in the southern Atlantic Ocean. The proposed de- lay-difference model provides a good fit to the data of southern Atlantic albacore stock and may be a useful choice for the assessment of regional albacore stock.展开更多
文摘Objective:To evaluate exploitation status of the stocks of demersal fishes in Omani artisanal fisheries.Methods:Time-series data between 2005 and 2014 on catches and effort represented by the number of fishing boats were used to estimate catch per unit effort and maximum sustainable yields applying Schaefer surplus production model.Regression analyses were made online using GraphPad software.Results:The study revealed that increasing the number of boats on the fishery caused a decrease of catch per unit effort of some species.Maximum sustainable yields and exploitation status were estimated for these species applying.Conclusions:Some demersal fish species were found to be caught in quantities exceeding maximum sustainable yields during some fishing seasons indicating overexploitation of their stocks.
基金supported by the National Key R&D Program of China(2018YFD0900906)the Guangdong Natural Science Foundation(2016A030313752)+1 种基金the Fund of Southern Marine Science and Engineering Guangdong Laboratory(Zhanjiang)(ZJW-2019-08)the Scientific Research Foundation for Talent Introduction,Guangdong Ocean University(1212037).
文摘In order to develop a method that apply sampling survey data randomly obtained at fishing ports to fish stock assessments,based on fish landing surveys conducted at fishing ports in the northern South China Sea(SCS),19 Threadfin porgy(Evynnis cardinalis)catch per unit effort(CPUE)datasets were collected for fishing vessels with different gear types and engine powers and incorporated into surplus production models.Considering only the fitting performance,the Schaefer model had the best overall goodness of fit,followed by the Fox,CYP,W-H,and Schnute models.Among fishing vessels with different gears and engine powers,the data were best fitted for single-trawl vessels powered by 301-400-kW engines and for gillnet vessels powered by>200-kW engines.Eight model expressions were superior and selected for subsequent analyses based on their goodness of fit and relative residuals.The Kobe plot analysis results showed an optimistic fish stock status when using the four model expressions,required more caution when using three model expressions and output pessimistic estimations using one model expression.Considering the incomplete information acquired,a compromising decision-making method was used to derive a 2017 northern SCS E.cardinalis total allowed catch(TAC)of 44,691.21 t.The different conclusions drawn from estimations using CPUEs reflect variable exploitation and utilization fish stock statuses among fishing vessels with different gears and engine powers.Hence,the fishing operations were grouped according to their CPUE relationship,and recommendations regarding optimum fishing efforts were assigned to the groups following a fundamental principle:to improve fishery TAC management,fishing efforts should be reduced if the fish stock assessment is pessimistic and maintained if the assessment is optimistic.This study providing a feasible technical method for the TAC management of China’s offshore fisheries.
文摘为了解和掌握月相对渔业产量或单位捕捞努力量渔获量(catch per unit effort,CPUE)的影响规律,利用2016—2019年(每年3月2日—11月29日)马达加斯加西海岸底拖网独角新对虾(Metapenaeus monoceros)和2017—2020年(每年6月15日—10月9日)西白令海中层拖网狭鳕(Theragra chalcogramma)的渔业生产数据,结合基于圆形统计的广义线性模型(GLM)和基于时间序列的广义加性模型(GAM)2种不同的月相量化和统计的方法,分析月相对拖网渔业CPUE的影响。结果表明:月相对独角新对虾的CPUE具有显著性影响(P<0.05),2种方法得出的影响趋势较为一致,较高CPUE出现在上弦月;基于圆形统计的GLM显示,月相对狭鳕CPUE具有显著性影响(P<0.05),较高CPUE出现在新月期,而基于时间序列的GAM显示,月相对狭鳕CPUE的影响不显著(P>0.05);交叉验证显示,基于圆形统计的GLM平均绝对误差(E_(MA))和均方根误差(E_(RMS))均小于基于时间序列的GAM,而GLM分析的决定系数R~2则大于GAM,表明前者的拟合具有更好的准确性、稳定性和拟合优度。研究表明,当周期性循环变量(月份、月相和小时等)具有较弱的显著性时,使用基于圆形统计的GLM更能反映月相对拖网渔业CPUE的影响。
文摘拦河筑坝所导致的物理阻隔和生态阻隔是影响鱼类迁徙的关键因素。圆口铜鱼Coreius guichenoti(Sauvage&Dabry de Thiersant,1874)作为长江上游重要的河流性洄游鱼类,其迁徙不可避免受到金沙江下游向家坝和溪洛渡大型水电站蓄水的影响。关于向家坝和溪洛渡蓄水是否会显著阻隔圆口铜鱼个体的下行以及不同年龄个体之间受阻隔的影响是否存在差异,迄今为止,还未有相关报道。本文拟通过2012—2014年对长江上游永善江段和宜宾江段圆口铜鱼年龄结构变动的研究,探讨向家坝和溪洛渡蓄水对圆口铜鱼不同年龄个体下行阻隔的影响程度。结果表明:1)向家坝和溪洛渡蓄水对圆口铜鱼下行产生了明显的阻隔效应;2)向家坝和溪洛渡蓄水对1龄个体的下行阻隔最明显且最严重;3)与单一的大型水库和大坝相比,多个梯级的大型水库和大坝会对圆口铜鱼的下行产生更为严重的阻隔效应。本文拟为金沙江下游圆口铜鱼的资源保护提供基础数据支持。
文摘分析南极磷虾分布与环境因子的非线性和空间非静态性关系,对南极磷虾的高效捕捞和管理具有重要意义。本研究基于“龙腾”船2015、2016年在南设得兰群岛捕捞作业的渔捞日志数据,应用广义加模型(Generalized additive model,GAM)和地理权重回归模型(Geographical weighted regression,GWR)探究南极磷虾(Euphausia superba)渔场分布与环境因子的非线性和空间非静态性关系,并比较这2种模型的模拟性能,为南极磷虾的渔场渔情预报、资源评估和渔业管理提供基础数据。GAM模型结果显示,2015、2016年单位捕捞努力量渔获量(Catch per unit effort,CPUE)与作业水深均呈显著负相关关系(P<0.01),表明在作业水深范围内,南极磷虾在较浅水域集群密度较高;2015年CPUE与表层水温呈显著正相关关系(P<0.01),但在2016年呈显著负相关关系(P<0.01),推测是由于2年调查作业位置不同所致;CPUE与离岸距离关系不显著(P≥0.05)。GWR模型结果显示,作业水深对CPUE的影响无显著的空间变化(P>0.05);海水表温和离岸距离对CPUE的影响具显著的空间变化(P<0.01),表明这2个因子对南极磷虾渔场分布的影响在空间上不连续,存在显著空间非静态性。GAM模型可用于研究资源分布与驱动因子的一般规律;GWR模型作为全局回归模型的有效补充,可用于探究一般规律不适合的特殊区域,便于发现资源分布的“热点”区域,未来在海洋生物资源分布研究中将有广阔的应用前景。
基金Supported by the Science and Technology Commission of Shanghai Municipality(Nos.08DZ1203101,08DZ1203102)the Shanghai University Knowledge Service Platform,Shanghai Ocean University Aquatic Animal Breeding Center(No.ZF1206)
文摘Two fishing methods including gillnetting and trawling to estimate attributes of fish assemblage were compared in Dianshan Lake from August 2009 to July 2010. Species composition dif fered significantly between the gears, with four significant contributors in gillnet catches and one in trawl catches. Trawling collected more proportions of benthic species by number and biomass than gillnetting. Size distribution was significantly influenced by fishing technique; gillnetting captured relatively less small-sized fishes and trawling captured less large-sized individuals. Trawling produced species richness closer to the one expected than gillnetting. On the whole, trawl catch was a quadratic polynomial function of gillnet catch and a significantly negative correlation was found between them, both of which varied as dif ferent polynomial functions of temperature. However, trawl and gillnet catches were significantly correlated only in one of five month groups. It is concluded that single-gear-based surveys can be misleading in assessments of attributes of fish assemblages, bottom trawling is a more ef fective gear for assessing fish diversity than benthic gillnetting, and using gillnet catches as an indicator of fish density depends on fishing season in the lake.
基金supported by the Fundamental Research Funds for the Central Universities of China (Grant No. 201022001)
文摘Delay-difference models are intermediate between simple surplus-production models and complicated age-structured models. Such intermediate models are more efficient and require less data than age-structured models. In this study, a delay-differ- ence model was applied to fit catch and catch per unit effort （CPUE） data （1975-2011） of the southern Atlantic albacore （Thunnus alalunga） stock. The proposed delay-difference model captures annual fluctuations in predicted CPUE data better than Fox model. In a Monte Carlo simulation, white noises （CVs） were superimposed on the observed CPUE data at four levels. Relative estimate error was then calculated to compare the estimated results with the true values of parameters a and fl in Ricker stock-recruitment model and the catchability coefficient q. a is more sensitive to CV than fl and q. We also calculated an 80% percentile confidence interval of the maximum sustainable yield （MSY, 21756 t to 23408 t; median 22490 t） with the delay-difference model. The yield of the southern Atlantic albacore stock in 2011 was 24122t, and the estimated ratios of catch against MSY for the past seven years were approxi- mately 1.0. We suggest that care should be taken to protect the albacore fishery in the southern Atlantic Ocean. The proposed de- lay-difference model provides a good fit to the data of southern Atlantic albacore stock and may be a useful choice for the assessment of regional albacore stock.
