Otolith chemistry is a useful natural tracer for discerning habitat-use of estuarine fishes. For Southern Flounder Paralichthys lethostigma, recent otolith chemistry studies have revealed a diversity of residency patterns across salinity gradients. However, the contribution of recruits with specific residency patterns to fisheries is poorly understood. The objectives of this study were to (1) use otolith chemistry from fishery-independent and fishery-dependent collections in Mobile Bay, Alabama, to classify lifetime residency patterns (i.e., freshwater, transient, estuarine) in Southern Flounder collected across a large estuarine salinity gradient (0–30 psu); (2) to test if Southern Flounder exhibited resident or migratory behavior by determining if lifetime residency patterns in fishery-independent samples matched expected salinity patterns in the region of collection after accounting for annual variation in river discharge; and (3) to examine which residency patterns contributed to the commercial and recreational Southern Flounder fisheries in nearby coastal waters. Age-0 residency patterns in fishery-independent samples were strongly correlated with region of collection and annual river discharge, suggesting that the majority of Southern Flounder had resided in the same region in which they spent their age-0 growth phase. Southern Flounder with a combination of freshwater and estuarine salinity signals and classified as “transient” did not appear to have conducted large-scale movements across salinity gradients, but instead resided in regions of the estuary experiencing seasonal fluctuations in salinity. The majority (57%) of commercially and recreationally harvested Southern Flounder were transients, while a minority (39%) were estuarine residents and lifetime freshwater residents (4%) were rarely harvested. Results from this study suggest that Southern Flounder settle in and remain in the certain habitats during the estuarine residency phase. Given the lack of movement across habitats, future efforts to understand how habitat-specific conditions (e.g., abiotic, biotic, fishing exploitation) affect vital rates seems warranted for a species currently experiencing population declines.

中文翻译：

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南方比目鱼生活史的多样性和对不同河口盐度带渔业的贡献

耳石化学是一种有用的天然示踪剂，可用于识别河口鱼类的栖息地使用情况。对于南方比目鱼Paralichthys lethostigma, 最近的耳石化学研究揭示了跨盐度梯度的驻留模式的多样性。然而，人们对具有特定居住模式的新兵对渔业的贡献知之甚少。本研究的目的是 (1) 使用来自阿拉巴马州莫比尔湾的独立于渔业和依赖于渔业的收集品中的耳石化学，对在大型河口收集的南部比目鱼的终生居住模式（即淡水、瞬态、河口）进行分类盐度梯度（0–30 psu）；(2) 在考虑河流流量的年度变化后，通过确定与渔业无关的样本中的终生居住模式是否与采集区域的预期盐度模式相匹配，来测试南方比目鱼是否表现出定居或迁徙行为；(3) 检查哪些居住模式有助于附近沿海水域的商业和休闲南方比目鱼渔业。与渔业无关的样本中的 0 龄居住模式与采集区域和年度河流流量密切相关，这表明大多数南方比目鱼生活在它们度过 0 龄生长阶段的同一区域。具有淡水和河口盐度信号组合并被归类为“瞬态”的南方比目鱼似乎没有在盐度梯度上进行大规模运动，而是居住在经历盐度季节性波动的河口区域。大多数（57%）商业和休闲捕捞的南方比目鱼是短暂的，而少数 (39%) 是河口居民，而终身淡水居民 (4%) 很少被捕获。这项研究的结果表明，南方比目鱼在河口居住阶段定居并留在某些栖息地。鉴于缺乏跨栖息地的运动，对于目前正在经历种群下降的物种，未来似乎有必要努力了解特定栖息地条件（例如，非生物、生物、捕鱼开发）如何影响生命率。