珠海外伶仃海洋牧场渔业资源分布的环境效应

Environmental effects of the distribution of fishery resources in Wailingding marine ranching, Zhuhai

  • 摘要: 【目的】 探究珠海外伶仃海洋牧场渔业资源分布的环境效应,为南海近岸渔业资源保护、增殖与科学管理提供理论依据。【方法】 在外伶仃岛设置10个调查站点,分别于2020年春季(4月)和秋季(9月)开展海洋生态环境与渔业资源调查。温度、盐度和pH分别采用温度计、盐度计和pH计现场测定,溶解氧浓度使用碘量滴定法现场测定。溶解无机氮浓度采用萘乙二胺分光光度法和镉柱还原法测定,磷酸盐浓度采用磷钼蓝分光光度法测定,叶绿素a浓度采用分光光度法测定。采用全片计数法进行定量计数并结合水体体积换算得到浮游植物密度,以个体数表示浮游动物密度。渔业资源调查采用底拖网单拖渔船进行。通过方差膨胀因子(VIF)对环境因子进行共线性检验,剔除高共线性变量,并进行广义可加模型(GAM)分析和模型评价,分析珠海外伶仃海洋牧场渔业资源时空分布与海洋环境的关系。【结果】 共线性检验结果显示,盐度、温度和溶解氧浓度VIF>10,存在严重共线性,最终保留叶绿素a浓度、溶解氧浓度、深度、pH、溶解无机氮浓度、磷酸盐浓度、浮游植物密度和浮游动物密度用于构建GAM模型。影响因子筛选结果显示,溶解氧浓度是影响单位捕捞努力量渔获量(CPUE)的最主要因子,贡献率为25.3%,其次为叶绿素a浓度(24.5%)和浮游动物密度(16.3%),深度对CPUE的贡献率最低(6.3%)。GAM分析结果显示,珠海外伶仃海洋牧场渔业资源主要分布在溶解氧浓度6.700~8.100 mg/L,叶绿素a浓度0.500~1.200 mg/m3,浮游动物密度230.000~450.000 pcs/m3,深度6.500~10.000 m的海域。CPUE随溶解氧浓度的升高呈先降低后升高的变化趋势,CPUE随叶绿素a浓度的升高逐渐升高,CPUE随浮游动物密度的升高呈先升高后趋于平缓的变化趋势,CPUE随深度升高逐渐降低。珠海外伶仃海洋牧场在春季和秋季渔业资源空间分布均表现出一定规律性,主要集中在岛礁东部与南部海域,且秋季的CPUE高于春季。春季渔业资源主要分布于外伶仃岛近岸南部和东部海域。秋季渔业资源则更多集中在近岸东部海域,该区域的CPUE水平较高。【结论】 珠海外伶仃海洋牧场渔业资源受各项环境因子的协同调控,溶解氧浓度是最关键的驱动因子,其次为叶绿素a浓度、浮游动物密度和深度。珠海外伶仃海洋牧场渔业资源在秋季高于春季,主要聚集于岛礁东部与南部海域。渔业资源存在季节性变化趋势,伏季休渔制度对牧场生态恢复具有积极作用。

     

    Abstract: 【Objective】 The aim of this study was to explore the environmental effects of the distribution of fishery resources in the Wailingding marine ranch in Zhuhai, which could provide theoretical basis for the protection, proliferation and scientific management of coastal fishery resources in the South China Sea. 【Method】 Ten survey sites were set up on Wailingding Island, and marine ecological environment and fishery resources surveys were carried out in spring(April) and autumn(September) of 2020. Temperature, salinity and pH were measured on site using thermometers, salinity meters and pH meters respectively, and dissolved oxygen concentration was measured on site using iodine titration. Dissolved inorganic nitrogen concentration was determined by naphthylethylenediamine spectrophotometry and cadmium column reduction method, phosphate concentration was determined by phosphomolybdenum blue spectrophotometry, and chlorophyll a concentration was determined by spectrophotometry. Phytoplankton density was obtained by quantitative counting using the whole-piece counting method and converted by water volume, and zooplankton density was expressed as individual numbers. The fishery resource survey was conducted using a bottom trawl single trawler. Variance inflation factor(VIF) was used to test the collinearity of environmental factors, and variables with high collinearity were screened out. Generalized additive model(GAM) analysis and model evaluation were performed to analyze the relationship between the spatiotemporal distribution of fishery resources in Wailingding marine ranching and the marine environment. 【Result】 The collinearity test results showed that the VIF of salinity, temperature and dissolved oxygen concentration were all >10, indicating serious collinearity. Finally, chlorophyll a concentration, dissolved oxygen concentration, depth, pH, dissolved inorganic nitrogen concentration, phosphate concentration, phytoplankton density and zooplankton density were retained to construct the GAM model. The results of influencing factor screening showed that dissolved oxygen concentration was the most important factor affecting the catch per unit fishing effort(CPUE), with a contribution rate of 25.3%, followed by chlorophyll a concentration(24.5%) and zooplankton density(16.3%). The contribution rate of depth to CPUE was the lowest, at 6.3%. The results of GAM analysis showed that the fishery resources of the Wailingding marine ranching in Zhuhai were mainly distributed in the sea areas with dissolved oxygen concentration of 6.700-8.100 mg/L, chlorophyll a concentration of 0.500-1.200 mg/m3, zooplankton density of 230.000-450.000 pcs/m3, and depth of 6.500-10.000 m. CPUE showed a trend of decreasing first and then increasing with the increase of dissolved oxygen concentration, increasing with the increase of chlorophyll a concentration, increasing first and then tending to be gentle with the increase of zooplankton density, and decreasing with the increase of depth. The spatial distribution of fishery resources in the Wailingding marine ranching in Zhuhai showed a certain regularity in spring and autumn, mainly concentrated in the eastern and southern waters of the islands and reefs, and the CPUE in autumn was higher than that in spring. In spring, fishery resources were mainly distributed in the southern and eastern waters near the coast of Wailingding Island. In autumn, the fishery resources were more concentrated in the eastern coastal waters, and the CPUE level in this area was relatively high. 【Conclusion】 The fishery resources of the Wailingding marine ranching in Zhuhai are regulated by various environmental factors. Dissolved oxygen concentration is the most critical driving factor, followed by chlorophyll a concentration, zooplankton density and depth. The fishery resources of the Wailingding marine ranching in Zhuhai are higher in autumn than in spring, and are mainly concentrated in the eastern and southern waters of the islands and reefs. There is a seasonal trend in fishery resources, and the summer fishing moratorium system has a positive effect on the ecological restoration of the ranching.

     

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