大西洋大眼金枪鱼适宜生境空间对延绳钓渔获率影响
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摘要
金枪鱼适宜垂直生境空间对延绳钓捕捞效率有明显影响,而金枪鱼垂直分布主要受海洋环境条件影响,因此本文模型分析环境变量对延绳钓大眼金枪鱼渔获率的影响,评估适宜生境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30~50oW。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250m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200m,延绳钓渔获率递增;温跃层下界深度和深度差超过200m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200m和50m。研究结果证实在大眼金枪鱼适宜生境空间受限时,延绳钓渔获率会更高。研究结果揭示对延绳钓CPUE的分析时要考虑金枪鱼适宜生境空间。
The vertical habitat limit of tuna has significantly effect on the longline catchability,which primarily influenced by oceanographic feature. In order to support the operation of longline and fishery management, several key environment factors were adopt to evaluate the influence of habitat preference and limits on catch rates of longlines in the tropical Atlantic Ocean. Regression model was used to determine the significant relationship between environment and longline catch rate, express as catch per unit fishing effort(CPUE). Generalized additive model(GAM) was adopted to evaluate the significant environment nonlinear effect on CPUE. Model results revealed the environment and spatio-temporal factors had significant effect on catch rates, and the relationship was nonlinear.
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