基于LeMaRns模型的热带中西太平洋中上层生态系统动态分析

Analysis of pelagic ecosystem dynamics in the western and central tropical Pacific based on the LeMaRns model

摘要:

目的 热带中西部太平洋渔业资源丰富，是全球主要的金枪鱼渔业作业区域。为了解长期捕捞对中西太平洋中上层生态系统的影响，拟建立基于体长结构的生态系统模型LeMaRns，以模拟分析金枪鱼渔业对常见鱼种和生态指标的影响。方法 设计F=0 (无捕捞活动)、F=F_msy(最大可持续产量时的捕捞死亡率)、F=F_recent(最近几年的平均捕捞死亡率)、F=0.8F_msy和F=1.2F_msy 等5种捕捞策略对10个物种进行模拟捕捞，对资源状况进行10年预测。重点分析5种捕捞策略对生物量(B)、产卵群体生物量(SSB)等2个单鱼种指标以及大型鱼类指数(LFI)、平均最大长度(MML)、典型长度(TyL)、体长分位数(LQ)等4个生态指标的影响。结果 在无捕捞情况下 (F=0)，物种的生物量基本趋于平衡；在捕捞情况下，大眼金枪鱼、剑鱼、黄鳍金枪鱼、鲣和长鳍金枪鱼等金枪鱼类的生物量下降0.26%~99.75%；灰鲭鲨、平鳍旗鱼、印度枪鱼的生物量上升0.01%~12.51%；大青鲨的生物量上升36.74%，产卵群体生物量下降60%，其余物种的资源状况几乎无变化。在模拟捕捞的前6年，MML、TyL、LQ随着捕捞努力量的增大而增大，之后随着捕捞努力量的增大而减小；LFI随着捕捞努力量的增大未呈现下降趋势。结论 在当前捕捞强度下，热带中西太平洋生态系统未来10年中处于可持续状态。LeMaRns模型可用于分析大范围的海洋生态系统，为渔业管理提供基于生态系统的分析手段。

Abstract:

The western and central tropical Pacific Ocean is one of the most productive marine ecosystems and a principal tuna fishing area globally. To investigate the effects of fishing on the marine ecosystem's structure in this region, LeMaRns model, an ecosystem model based on body length structure, was developed. It simulated and analyzed the impacts of tuna fisheries on key species and ecosystem indicators. The model evaluated five fishing strategies, including F=0 (i.e. no fishing activity), F=F_msy (fishing mortality at maximum sustainable yield), F=F_recent (average fishing mortality in recent years), F=0.8F_msy, and F=1.2F_msy, with projections for 10 years on 10 species. The study analyzed the effects of these strategies on two single species indicators of biomass (B), spawning stock biomass (SSB) and four ecosystem indicators of Large fish indicators (LFI), Mean maximum length (MML), typical length (TyL) and length quantile (LQ). Findings indicated that the biomass of the species generally reached equilibrium at F=0. Under fishing pressure, the biomass of tuna species such as Thunnus obesus, Xiphias gladius, T. albacares, Katsuwonus pelamis and T. alalunga decreased by 0.26% to 99.75%, while that of Isurus oxyrinchus, Istiophorus platypterus, and Istiompax indica increased by 0.01% to 12.51%. The biomass of Prionace glauca increased by 36.74%, and the spawning stock biomass decreased by 60%. Other species' resource status remained largely unchanged. Over the first six years of simulated fishing, MML, TyL, and LQ initially increased with fishing effort and then decreased; LFI consistently increased. The study suggested that the western and central tropical Pacific ecosystem would be in a sustainable state under the recent fishing mortality over the next decade. The LeMaRns model can be used to simulate and analyze large-scale marine ecosystems, providing a valuable ecosystem-level approach for fisheries management.