通过模型分析环境变量对延绳钓大眼金枪鱼渔获率的影响,评估适宜垂直活动空间对大西洋大眼金枪鱼延绳钓渔获率的作用。首先采用回归分析检验环境变量对延绳钓渔获率(由单位捕捞努力渔获量(catch per unit fishing effort,CPUE)表示)的...通过模型分析环境变量对延绳钓大眼金枪鱼渔获率的影响,评估适宜垂直活动空间对大西洋大眼金枪鱼延绳钓渔获率的作用。首先采用回归分析检验环境变量对延绳钓渔获率(由单位捕捞努力渔获量(catch per unit fishing effort,CPUE)表示)的影响显著性,结合时空变量,采用GAM(generalized additive model)模型分析各变量对大眼金枪鱼CPUE非线性作用。模型结果表明,环境因子和时空变量对热带大西洋延绳钓大眼金枪鱼渔获率空间分布影响明显。大西洋大眼金枪鱼延绳钓的高渔获率月份出现在夏季和冬季,空间上在赤道以北和30?~50?W。12℃等温线深度对大眼金枪鱼延绳钓渔获率的影响表现为抛物线形状,高渔获率出现在深度较浅的250 m水层,随着12℃等温线深度的增加,大眼金枪鱼延绳钓渔获率降低。温跃层下界深度和深度差对大眼金枪鱼延绳钓渔获率的影响都是穹顶状。随着温跃层下界深度值和深度差由小变大至200 m,延绳钓渔获率递增;温跃层下界深度和深度差超过200 m后,延绳钓渔获率变小。温跃层下界深度和深度差对大眼金枪鱼延绳钓渔获率影响显著的水层分别是200 m和50 m。研究结果显示,12℃等温线深度和温跃层对热带大西洋延绳钓大眼金枪鱼渔获率影响是交叉的,在大眼金枪鱼适宜垂直活动水层受限到和延绳钓作业深度相同时,延绳钓渔获率最高;在适宜垂直活动空间过深或者过浅时,延绳钓渔获率都变小,但可以通过改变作业方式提高渔获率。采用延绳钓CPUE进行渔场和资源评估要考虑金枪鱼适宜垂直活动空间。展开更多
The variability of ocean circulation and sea surface temperature (SST) in the tropical Atlantic, especially in the Gulf of Guinea (GG), defines this region as exceptionally rich from an oceanographic perspective. The ...The variability of ocean circulation and sea surface temperature (SST) in the tropical Atlantic, especially in the Gulf of Guinea (GG), defines this region as exceptionally rich from an oceanographic perspective. The Guinea Current (GC), as the major surface current, plays a significant role in marine productivity and coastal upwelling in the GG. This coastal upwelling is known to influence the climate of the surrounding region, primary productivity and local fisheries. Studies on GC variability and its impact on this coastal upwelling have highlighted that the upwelling downstream of Cape Palmas is influenced by GC detachment, topographic variations and advective processes leading to significant vertical mixing. This study aims to analyze the interannual variability of the GC and its impact on coastal upwelling using the Coastal and Regional Ocean COmmunity model (CROCO). The model’s evaluation is conducted using observational data, specifically Geostrophic and EKman Current Observatory (GEKCO) and Ocean Surface Current Analysis (OSCAR) for currents, and Air-sea Fluxes for the global Tropic ocean-description (TROPFLUX) and Optimum Interpolation-Sea Surface Temperature (OI-SST) for temperature. Thus, the model evaluation indicates that it accurately replicates ocean circulation and SST patterns in the tropical Atlantic and the GG. The joint analysis of upwelling indices (surface and intensity) and the position of the GC core allowed us to conclude that the displacement of the GC core does indeed influence the upwelling indices in the northern part of GG. However, other oceanic and atmospheric mechanisms such as vertical diffusion and horizontal advection as proposed by previous studies may also affect the year-by-year variability of coastal upwelling in the northern GG.展开更多
与太平洋和印度洋不同,全球变暖下热带大西洋变化的研究较少。本文使用地球系统模型CESM(Community Earth System Model),发现全球变暖后热带大西洋在秋季的升温类似大西洋尼诺(Atlantic Ni?o)的正位相,即大西洋西部增暖幅度小于东部;...与太平洋和印度洋不同,全球变暖下热带大西洋变化的研究较少。本文使用地球系统模型CESM(Community Earth System Model),发现全球变暖后热带大西洋在秋季的升温类似大西洋尼诺(Atlantic Ni?o)的正位相,即大西洋西部增暖幅度小于东部;在夏季类似大西洋尼诺的负位相,即大西洋西部增暖幅度大于东部。利用覆盖(overriding)技术,分离了风应力、风速和CO2的直接热效应对海洋升温的作用,探讨了大西洋尼诺本身和全球变暖作用下类似大西洋尼诺正位相(下文简称"类大西洋尼诺升温")的形成机制。结果表明,这两种情况下的形成机制基本相同,风应力的变化是导致大西洋东部暖异常的主要机制。但两者之间也存在区别:1)全球变暖下海表温度的季节变化振幅减小,而大西洋尼诺时变化不大;2)全球变暖下西风异常主要集中在大西洋东部,而大西洋尼诺时主要集中在大西洋中部;3)除风应力外, CO2的热效应对类尼诺升温的变化也有一定影响。展开更多
海龟处于海洋生态结构的顶端,对海洋生态系统的多样性和稳定性起到了重要的调控作用。根据2009—2019年科学观察员对热带大西洋公海海域(15°S~15°N,15°W~45°W)金枪鱼延绳钓渔业的调查数据,分析海龟兼捕现象。结果发...海龟处于海洋生态结构的顶端,对海洋生态系统的多样性和稳定性起到了重要的调控作用。根据2009—2019年科学观察员对热带大西洋公海海域(15°S~15°N,15°W~45°W)金枪鱼延绳钓渔业的调查数据,分析海龟兼捕现象。结果发现:共误捕到蠵龟(Caretta caretta)、大西洋丽龟(Lepidochelys kempii)和棱皮龟(Dermochelys coriacea)等3种累计108只,其中死亡32只。年兼捕率范围为0.0016~0.0693只/千钩,直接咬钩和被支绳缠绕是兼捕的主要方式;兼捕时间上存在一定季节性差异,高兼捕率(bycatch per unit effort,BPUE)发生在10月到翌年5月;赤道以北兼捕率年际间出现波动,但总体变化幅度不大,赤道以南兼捕率年际差异较大,2009—2013年间未发现海龟兼捕,但自2013年后南纬BPUE增长趋势明显,于2015年达到最大值,随后BPUE逐渐降低,2019年到达最小值;海龟兼捕易受到月相强度的影响,往往在满月或接近满月的环境下兼捕现象明显增多;某些特定温度区间会出现不同种类海龟的兼捕,棱皮龟在水温24~26℃时兼捕更易发生,丽龟兼捕则在26~27℃间更为集中。此外,还探究了近年来中国船队海龟兼捕存活率提高的原因,建议今后为有效降低热带大西洋金枪鱼延绳钓渔业中海龟兼捕,应根据作业海域、目标鱼种和环境因子的不同适时调整相关养护对策。展开更多
文摘The variability of ocean circulation and sea surface temperature (SST) in the tropical Atlantic, especially in the Gulf of Guinea (GG), defines this region as exceptionally rich from an oceanographic perspective. The Guinea Current (GC), as the major surface current, plays a significant role in marine productivity and coastal upwelling in the GG. This coastal upwelling is known to influence the climate of the surrounding region, primary productivity and local fisheries. Studies on GC variability and its impact on this coastal upwelling have highlighted that the upwelling downstream of Cape Palmas is influenced by GC detachment, topographic variations and advective processes leading to significant vertical mixing. This study aims to analyze the interannual variability of the GC and its impact on coastal upwelling using the Coastal and Regional Ocean COmmunity model (CROCO). The model’s evaluation is conducted using observational data, specifically Geostrophic and EKman Current Observatory (GEKCO) and Ocean Surface Current Analysis (OSCAR) for currents, and Air-sea Fluxes for the global Tropic ocean-description (TROPFLUX) and Optimum Interpolation-Sea Surface Temperature (OI-SST) for temperature. Thus, the model evaluation indicates that it accurately replicates ocean circulation and SST patterns in the tropical Atlantic and the GG. The joint analysis of upwelling indices (surface and intensity) and the position of the GC core allowed us to conclude that the displacement of the GC core does indeed influence the upwelling indices in the northern part of GG. However, other oceanic and atmospheric mechanisms such as vertical diffusion and horizontal advection as proposed by previous studies may also affect the year-by-year variability of coastal upwelling in the northern GG.
文摘海龟处于海洋生态结构的顶端,对海洋生态系统的多样性和稳定性起到了重要的调控作用。根据2009—2019年科学观察员对热带大西洋公海海域(15°S~15°N,15°W~45°W)金枪鱼延绳钓渔业的调查数据,分析海龟兼捕现象。结果发现:共误捕到蠵龟(Caretta caretta)、大西洋丽龟(Lepidochelys kempii)和棱皮龟(Dermochelys coriacea)等3种累计108只,其中死亡32只。年兼捕率范围为0.0016~0.0693只/千钩,直接咬钩和被支绳缠绕是兼捕的主要方式;兼捕时间上存在一定季节性差异,高兼捕率(bycatch per unit effort,BPUE)发生在10月到翌年5月;赤道以北兼捕率年际间出现波动,但总体变化幅度不大,赤道以南兼捕率年际差异较大,2009—2013年间未发现海龟兼捕,但自2013年后南纬BPUE增长趋势明显,于2015年达到最大值,随后BPUE逐渐降低,2019年到达最小值;海龟兼捕易受到月相强度的影响,往往在满月或接近满月的环境下兼捕现象明显增多;某些特定温度区间会出现不同种类海龟的兼捕,棱皮龟在水温24~26℃时兼捕更易发生,丽龟兼捕则在26~27℃间更为集中。此外,还探究了近年来中国船队海龟兼捕存活率提高的原因,建议今后为有效降低热带大西洋金枪鱼延绳钓渔业中海龟兼捕,应根据作业海域、目标鱼种和环境因子的不同适时调整相关养护对策。
文摘为提高大西洋热带海域长鳍金枪鱼(Thunnus alalunga)渔场预报的准确率,对K最近邻(k nearest neighbor,KNN)、逻辑斯蒂回归(logistic regression,LR)、决策与分类树(classfication and regression tree,CART)、梯度提升决策树(gradient boosting decision tree,GBDT)、随机森林(random forest,RF)、支持向量机(support vector machine,SVM)和Stacking集成(stacking ensemble learning,STK)共7个模型的预报性能进行了对比分析。该7个模型利用2016~2019年在大西洋公海海域(19°16′S~16°21′N;46°27′W~2°09′E)作业的13艘中国远洋延绳钓渔船的渔业数据,结合0~500 m不同水层的温度、盐度、溶解氧、叶绿素a浓度、海表面风速、涡动能和混合层深度数据建立。各模型取75%数据作为训练数据,25%为测试数据,采用预报准确率(accuracy,ACC)与接受者操作特征曲线下面积(area under curve,AUC)评价建立的单位努力量渔获量(catch per unit of effort,CPUE)与海洋环境因子关系模型的性能。结果表明:(1)STK模型对大西洋长鳍金枪鱼渔场的预报性能相比其他模型明显提高,ACC为75.92%,AUC为0.742;(2)基于STK模型预测得到的中心渔场范围总体上与实际作业渔场一致;(3)影响大西洋长鳍金枪鱼渔场分布的海洋环境因子主要为100 m水层的温度、盐度,以及100、150、500 m水层的溶解氧。研究表明STK模型对大西洋长鳍金枪鱼渔场的预报准确率较高,性能良好。
