Application of ocean color remote sensing products in estimation of fishing production potential in Lake Qinghai

Abstract

鱼产潜力可为渔业资源保护和管理提供科技支撑,传统的鱼产潜力估算方法在大型湖泊中往往成本高、采样率低、时效差.本研究基于2018—2020年非冰封期(5—10月)在青海湖的实测数据,通过提取和校对海洋水色遥感MODIS卫星数据反演产品(1 km分辨率)并结合垂向归纳模型(VGPM)构建了青海湖浮游植物初级生产力及鱼产潜力估算模型,估算的浮游植物初级生产力与实测值对比的平均相对误差小于25%.利用该模型估算2018—2020年非冰封期青海湖基于浮游植物初级生产力的鱼产潜力并分析其时空分布规律,结果显示青海湖鱼产潜力在5—10月呈现先增加后减少的季节波动规律,最大值出现在夏季(7—8月);空间分布上呈现湖心小,岸边及靠近入湖支流河口区域大的分布状态,全湖总鱼产潜力月均变化范围为2.5万~17.6万t.鱼产潜力的时空分布规律主要受气温、外源营养物质、裸鲤摄食等影响.研究表明青海湖非冰封期的鱼类资源承载力年累计值可达45.8万t,明显高于现有裸鲤资源的现存量和历史产量高峰值,表明青海湖仍然具备很大的鱼类资源承载力与增殖空间.本研究为同类型的大型高原湖泊基于卫星遥感的高效长期鱼产潜力监测估算提供了范例,为青海湖“封湖育鱼”政策制定和增殖放流保护决策提供参考.;Estimation of fish production potential (F_p) can provide scientific and technological support for fishery conservation and management, while traditional estimating methods of F_p in large lakes are often costly with low representativeness and time efficiency. This study estimated F_p of naked carps (Gymnocypris przewalskii) in Lake Qinghai,the largest plateau lake of China,based on the evaluation of chlorophyll-a, primary productivity of phytoplankton(PP) using VGPM (vertically generalized production model) via ocean color remote sensing products from MODIS satellites (1 km resolution) during the non-freeze period (May to October) from 2018 to 2020 surveyed field data. The average relative error is within 25% between the simulated and observed PP. The F_p results showed a seasonal fluctuation increasing first and then decreasing during the non-freeze period from 2018 to 2020, with the maximum values usually occurring in summer (July to August). The spatial distribution showed smaller F_p appeared in the middle of the lake and larger in the shore and near the estuary of Lake Qinghai tributaries, the gross weight ranged from 25000 to 176000 tons monthly. The temporal and spatial distribution of F_p was mainly affected by temperature, exogenous nutrients and fish feeding characteristics. TheF_p capacity in Lake Qinghai can support more than 458000 tons of naked carps annually, which is higher than the history and present fish resource, indicating enough fish proliferate and recovery space in Lake Qinghai. This study provides scientific and technological support for the strategies making of the fishing ban, lake closing, and fish restocking, and provides a case study for the effective estimation ofF_p based on remote sensing in the same type of large lakes.