赤道太平洋中部围网自由群的空间点模式的影响因子

The influence factors of spatial point patterns of purse seine free school in the Central Equatorial Pacific Ocean

赤道太平洋中部是我国围网渔船主要作业的海域之一,对围网自由群资源分布的影响因子的掌握非常重要。根据我国围网船队2015年渔捞日志,以空间点密度作为资源丰度的指标,选取几个相对重要因子(离岸距离、混合层深度、海表温度和净初级生产力),采用相对密度估计和点过程模拟方法,计算各因子对自由群资源密度的影响曲线和资源密度最优回归方程。结果显示,(1)围网自由群栖息偏好环境:离岸距离为70~250 km,海表温度为29.7~30.1°C,混合层深度为35.5~42 m,净初级生产力为200~280 mg C/(m2·d)。(2)资源密度在离岸距离为0~70 km之间快速上升,70~250 km保持小幅上升,离岸距离大于250 km后资源密度平稳下降;资源密度在海表温度为28.5~29.8°C,随着海表温度增加而增加,而30.2~31.5°C之间随机分布;净初级生产力为150~280 mg C/(m2·d),资源密度随之增加,而净初级生产力大于280 mg C/(m2·d)后资源密度下降;在混合层深度为30~37 m间为正相关上升,在37~51 m为负相关。(3)对资源密度贡献的重要性因子排列顺序依次为离岸距离>净初级生产力>混合层深度>海表温度。

There is one of the main areas of Chinese purse seine in the Central Equatorial Pacific Ocean. The fishing efforts for the free school fish stocks will be the trend of purse seine. To understand the environmental factors,which would affect the distribution of free school stock, is becoming more and more important. The free school stock is harder to catch than other types of fish, and the rate of failing sets is very high. This paper replaces the Catch per unit effort（CPUE）with the spatial points density as the index of stock abundance. The density of spatial points is treated as response variable, and we try to find out some significant variables from environmental factors based on the logbooks of Chinese Purse Seine fleets in 2015. Some factors are obtained as independent variables based on our experience or research articles, these variables are respectively： the distance to land（DIS）, sea surface temperature（SST）, net primary production（NPP） and mixed layer depth（MLD）. First, the nonparametric estimate to these factors are calculated from relative covariate intensity function（rhohat） method. Second, using point process model（ppm） function of these factors, the intensity regression equation is given. The results show that：（1） The favorite environmental range of these variables, are 70–250 km in DIS, are 29.7–30.1 °C in SST, are200–280 mg C/（m2·d） in NPP, and are 35.5–42 m in MLD, respectively.（2） There are positive relationships between the free school stock abundance with DIS within 0–70 km, SST within 28.5–29.8 °C, NPP within150–280 mg C/（m2·d）, and MLD within 30–37 m, while there are negative relationships between the free school stock abundance with DIS above 250 km, NPP above 280 mg C/（m2·d）, MLD above 37 m. And there are a random relationship between the free school stock abundance with SST above 30.2 °C.（3）We get the optimal free school stock abundance regression equation of these factors through stepwise regression based on the AIC method.Among the environment factors that influenced the free school stock abundance, the order of importance factor is DIS〉NPP〉MLD〉SST.