站位设计对北部湾产卵场海域渔业资源密度评估的影响

Impact of Station Design on the Assessment of Fishery Resource Density in the Spawning Grounds of the Beibu Gulf

  • 摘要:
    目的 本研究旨在确定北部湾东北部产卵场海域的最佳调查站位设计和最小站位数量,以实现最大代表性,并量化不同调查季节和抽样努力变化所引起的不确定性。
    方法 基于2014年以来春、秋两季共6个航次的渔业资源调查数据,以4种生物类群(鱼类、虾类、蟹类和头足类)为研究对象,以相对估计误差(REE)、相对偏差(RB)和设计效应(deff)为评价指标,利用kriging插值、计算机模拟和重抽样分析简单随机抽样设计(D1)、基于水深(D2)、功能区(D3)、地理边界(D4)、水深+地理边界(D5)、以及30′×30′空间分辨率(D6)等6种调查站位设计随站位数量和调查时间的变动对4种生物类群资源密度估算的影响,量化抽样努力和生物类群资源密度之间的关系。
    结果 现行的D6方案对4种生物类群资源密度的估计具有较好的稳定性,不受调查时间和站位数的影响。当调查站位数量相同时,D6方案的REE和deff最小,且随时间变化的稳定性最优,但头足类和蟹类RB值可能被高估(RB>8)。此外,不同站位抽样设计随调查站位数量的增加,REE变化趋势有所不同,D1~D5方案均出现一致性下降,D6则无明显变化。
    结论 当站位设计能够与4种生物类群的空间分布关键特征相匹配时,该站位设计可以提高调查精度。在站位数量和调查时间的双重不确定性下,最佳站位设计和最小调查站位数量随调查目标的变化而变化。兼顾调查精度和成本考虑,D6是目前北部湾东北部海域春秋两季站位数≥12个时调查4个海洋生物类群的优先方案。

     

    Abstract: Independent fishery surveys serve as a crucial pathway to ascertain the status of fishery resources within aquatic germplasm resource conservation areas. A well-designed sampling approach makes it possible to not only reduce the disturbance to fishery resources but also mitigate potential adverse effects on the ecosystem. We used fisheries data from single-vessel bottom trawl surveys conducted in the northern Beibu Gulf. The survey times including six voyages: spring (May) and autumn (September) of 2014, spring (April) and autumn (September) of 2018, autumn (November) of 2020, and spring (March) of 2021. We selected fish, cephalopods, shrimp, and crabs as our subjects of study. The resource density (kg/km2) of these groups was the target for our investigation, aiming to analyze the stability of the current station design over time. Additionally, we employed the ordinary kriging (OK) interpolation method to simulate the "true" distribution of resource densities for different biological communities. Based on this, the study established a simulation framework with six sampling designs: simple random sampling (D1), stratified random sampling by depth (D2), stratified random sampling by conservation area characteristics (D3), stratified random sampling by conservation area geographical boundaries (D4), stratified random sampling combining depth and geographical boundaries (D5), and stratified random sampling with a 30′×30′ spatial resolution (D6). We used the design effect (deff), relative estimation error (REE), and relative bias (RB) metrics to evaluate these designs, in an effort to test the accuracy and precision of different sampling designs on the assessment results. First, our research found that the current station design (D6) is not affected by temporal changes or the number of stations, demonstrating good stability in estimating the resource density of the four taxa in the area. When a comparable number of stations are deployed for the survey, the REE and deff values obtained using the D6 scheme are consistently smaller than those of D1 through D5. Although the RB values for cephalopods and crabs investigated using D6 may be overestimated (RB>8), D6 still exhibits better temporal stability than D1 through D5. Second, different station designs showed different trends in REE as the number of stations increased. The REE of D1 through D5 consistently declined, whereas D6 did not exhibit a clear, consistent trend of either decline or increase. Third, the survey accuracy of different station designs is closely related to the spatial distribution of the taxa. Since the distribution of some taxa does not consistently follow isobaths over time, D2 is deficient in temporal stability. Our study suggests that using D3 for cephalopod surveys should be approached with caution. The results show that when the station design is well-matched with the spatial distribution of various groups, survey accuracy can be significantly improved. We believe that the optimal station design varies slightly with both time and the number of stations. When the requirement is to deploy 9 stations, we advise implementing the D4 plan for conducting fishery resource surveys during the autumn voyage. For the spring season, no specific recommendation is made, as the optimal station design fluctuates among different species groups. However, when deploying either 12 or 15 stations, the D6 plan emerges as the preferred option for investigating the resource density of the four species groups in both spring and autumn, as its design is intended to maximize benefits. This study can provide a valuable reference for optimizing sampling designs in aquatic germplasm resource conservation areas.

     

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