Sampling designs for collection of shark size composition data are needed to fill one of the primary knowledge gaps hampering management of shark fisheries in Central America. These designs need to be tailored towards multi-species fisheries with highly structured landings, which are driven by buyer demand in port. In addition, due to the difficulty of maintaining catch quality outdoors in a tropical environment, the designs ideally would have minimal impact on the often-rapid catch landing process. In this study, simulations based on data from exhaustively sampled landings of Costa Rican mediana escala (78 landings) and avanzada (21 landings) commercial longline vessels were used to test single-cluster systematic sampling designs for estimating size (commercial weight category) composition of retained catches of shark species, as well as of other taxa present in landings with sharks. The wide range in numbers of sharks per landing led to sampling designs for which the frequency of within-landing sampling depended on the number of sharks to be landed. Designs for shark-only sampling and sampling of all taxa were tested. For the mediana escala fleet component, these designs performed well in terms of absolute relative error (ARE) for common species in the landings, including the silky shark, the dominant shark species, and swordfish, striped marlin and yellowfin tuna. There was less than a 5% chance that the ARE would exceed 0.2 for most weight categories of these species, even at the lowest sampling frequency. For all but the large weight category of striped marlin, there was only a 2% chance (or less) that the ARE would exceed 0.3. These results suggest that a single sampling design can be implemented for this fleet component to obtain estimates of the size composition of common shark and non-shark species, alike, in landings with sharks. For relatively uncommon shark species in the landings, such as hammerhead and the pelagic thresher sharks, the same sampling designs generally resulted in higher ARE, except for the dominant weight categories (small hammerhead sharks and large pelagic thresher sharks). However, the level of error itself associated with these designs may still be acceptable, depending on management needs; ARE can provide an overly pessimistic evaluation of performance for uncommon species. For landings of the avanzada fleet component, the performance of the shark-only sampling scenarios for the silky shark was generally similar to the results obtained for the mediana escala fleet component, except for the large weight category, although performance for this weight category, as measured by error, might still be acceptable. However, differences in performance between the shark-only and the all-fish scenarios for the silky shark raise the concern that the number of landings of avanzada vessels available for this analysis may be too small to make a definitive statement about sampling design performance for this fleet component. Development of sampling designs for the avanzada fleet component would benefit from an increase in sample size for analysis and a more detailed study of landing characteristics.

需要为收集鲨鱼大小组成数据进行抽样设计，以填补阻碍中美洲鲨鱼渔业管理的主要知识空白之一。这些设计需要针对具有高度结构化上岸量的多品种渔业进行量身定制，这是由港口买家需求驱动的。此外，由于在热带环境中难以在户外保持捕捞质量，理想情况下，这些设计对通常快速的捕捞着陆过程的影响最小。在这项研究中，模拟基于哥斯达黎加mediana escala（78 次着陆）和avanzada的详尽采样着陆数据（21 次上岸）商业延绳钓船用于测试单集群系统抽样设计，以估计鲨鱼物种的保留渔获量以及鲨鱼上岸时存在的其他类群的大小（商业重量类别）组成。每次着陆的鲨鱼数量范围很广，导致了采样设计，其中着陆内采样的频率取决于要上岸的鲨鱼数量。测试了仅鲨鱼抽样和所有分类群抽样的设计。对于中层阶梯船队组成部分，这些设计在上岸常见物种的绝对相对误差 (ARE) 方面表现良好，包括丝鲨、主要鲨鱼物种、箭鱼、条纹马林鱼和黄鳍金枪鱼。对于这些物种的大多数重量类别，即使在最低采样频率下，ARE 超过 0.2 的可能性也不到 5%。除了大重量的条纹马林鱼之外，所有的 ARE 超过 0.3 的可能性只有 2%（或更少）。这些结果表明，可以对该船队组成部分实施单一抽样设计，以估计常见鲨鱼和非鲨鱼物种的大小组成，类似地，在与鲨鱼一起登陆时。对于登陆时相对不常见的鲨鱼物种，例如双髻鲨和远洋长尾鲨，相同的抽样设计通常会导致较高的 ARE，除了主要的重量类别（小型双髻鲨和大型远洋长尾鲨）。然而，与这些设计相关的错误程度本身可能仍然是可以接受的，这取决于管理需要；ARE 可以对不常见物种的表现进行过于悲观的评估。对于登陆avanzada船队组件，除了大重量类别外，仅鲨鱼抽样方案的柔滑鲨鱼的性能与mediana escala船队组件获得的结果基本相似，尽管此重量类别的性能以误差衡量，可能还是可以接受的。然而，仅鲨鱼和全鱼情景之间的性能差异引发了人们的担忧，即可用于该分析的avanzada船只的登陆数量可能太少，无法就本次分析的抽样设计性能做出明确的陈述。车队组成部分。为avanzada开发抽样设计机队组成部分将受益于分析样本量的增加和对着陆特性的更详细研究。