Dispersal of a near-shore marine fish connects marine reserves and adjacent fished areas along an open coast

Marine species with pelagic larvae typically exhibit little population structure, suggesting long distance dispersal and high gene flow. Directly quantifying dispersal of marine fishes is challenging but important, particularly for design of marine protected areas (MPAs). Here, we studied kelp rockfish (Sebastes atrovirens) sampled along ~25 km of coastline in a boundary current-driven ecosystem and used genetic parentage analysis to identify dispersal events and characterize them, since the distance between sedentary parents and their settled offspring is the lifetime dispersal distance. Large sample sizes and intensive sampling are critical for increasing the likelihood of detecting parent-offspring matches in such systems and we sampled more than 6,000 kelp rockfish and analyzed them with a powerful set of 96 microhaplotype markers. We identified eight parent-offspring pairs with high confidence, and they included two juvenile fish that were born inside MPAs and dispersed to areas outside MPAs, and four fish born in MPAs that dispersed to nearby MPAs. Additionally, we identified 25 full-sibling pairs, which occurred throughout the sampling area and included all possible combinations of inferred dispersal trajectories. Intriguingly, these included two pairs of young-of-the-year siblings with one member each sampled in consecutive years. These sibling pairs suggest monogamy, either intentional or accidental, which has not been previously demonstrated in rockfishes. This study provides the first direct observation of larval dispersal events in a current-driven ecosystem and direct evidence that larvae produced within MPAs are exported both to neighboring MPAs and proximate areas where harvest is allowed.

具有浮游幼体的海洋物种通常种群结构极弱，这暗示其存在长距离扩散与高水平的基因交流。直接量化海洋鱼类的扩散过程颇具挑战但意义重大，尤其对于海洋保护区（Marine Protected Areas，MPAs）的规划设计而言。本研究针对边界流驱动生态系统中约25公里海岸带的海带岩鱼（Sebastes atrovirens）展开采样，并通过遗传亲权分析识别并表征扩散事件——因为定居亲本与其定居幼体之间的距离即为终生扩散距离。大样本量与高密度采样对于提升此类系统中检测亲代-子代配对的概率至关重要，为此我们共采集了6000余尾海带岩鱼，并采用包含96个微单倍型标记的高效分析体系对样本进行了基因分型。本研究成功鉴定出8对置信度极高的亲代-子代配对，其中2尾幼体诞生于海洋保护区内并扩散至保护区外区域，另有4尾幼体诞生于保护区后扩散至邻近的海洋保护区。此外，我们还鉴定出25对全同胞配对，这些配对分布于整个采样区域，涵盖了所有可推断的扩散路径组合。值得注意的是，其中包含2对当年生幼鱼的全同胞配对，每对中均有1尾个体在连续两年被采样到。此类同胞配对暗示了单配制的存在——无论是有意为之还是偶然形成，这在岩鱼物种中此前从未被证实过。本研究首次直接观测到了流驱动生态系统中的幼体扩散事件，并提供了直接证据：海洋保护区内繁育的幼体既会扩散至邻近的海洋保护区，也会被输送至允许捕捞的近岸区域。