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首页> 外文期刊>North American Journal of Fisheries Management >Assessing the Relationship between Gulls Larus spp. and Pacific Salmon in Central California Using Radiotelemetry
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Assessing the Relationship between Gulls Larus spp. and Pacific Salmon in Central California Using Radiotelemetry

机译：评估海鸥鸥属之间的关系。遥测法测定中部加利福尼亚州的鲑鱼和太平洋鲑鱼

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Predation by marine birds has resulted in substantial losses to runs of Pacific salmon Oncorhynchus spp., in some cases necessitating management action. Recovery of PIT tags on a seabird breeding colony (Ano Nuevo Island) indicated that western gulls Larus occidentalis prey upon federally listed Coho Salmon Oncorhynchus kisutch and steelhead O. mykiss in central California. Whereas salmonid populations in central California have decreased in recent decades, the western gull population on Ano Nuevo Island has increased. We observed gulls Larus spp. within estuaries to document predation and used radiotelemetry to examine gull movement in relation to the availability of salmonids. During 2008 and 2009, observed predation events of out- migrating salmonids by gulls were rare; 21 events occurred during 338 h of observations at two estuaries. During the prehatch and chick-rearing phases of breeding, which coincided with migration of salmonids from fresh to salt water, 74% of the detections of radio-tagged western gulls occurred within 25 km of Ano Nuevo Island, suggesting that the relative susceptibility of predation by western gulls using Ano Nuevo Island decreased with distance from the island. Western gull presence at creek mouths was greatest during daylight hours (91% of detections), while juvenile salmonids were present predominantly at night (65% of detections). The greatest overlap between western gulls and salmonids occurred at dusk, and predation of out-migrating salmonids was likely opportunistic. Deterring gulls from creek mouths when overlap between predator and prey might otherwise occur may buffer out-migrating salmonids from predation. Our results will inform management strategies to most effectively reduce the impacts of gull predation on central California salmonids.
机译：海洋鸟类的捕食已导致太平洋鲑鱼Oncorhynchus spp。的大量损失，在某些情况下需要采取管理行动。在海鸟繁殖地（Ano Nuevo岛）上恢复的PIT标签表明，西部海鸥Larus occidentalis捕食了加利福尼亚中部联邦政府列出的Coho Salmon Oncorhynchus kisutch和Steelhead O. mykiss。近几十年来，加利福尼亚中部的鲑鱼种群数量有所减少，而Ano Nuevo岛上的西部海鸥种群却有所增加。我们观察了鸥鸥属。在河口内记录捕食行为，并使用无线电遥测技术检查与鲑鱼的可利用性有关的海鸥运动。在2008年至2009年期间，很少观察到海鸥将鲑鱼迁出的捕食事件;在两个河口的338小时观测中发生了21个事件。在繁殖前期和育雏阶段，恰逢鲑鱼从淡水迁移到盐水中，放射性标记的西鸥检出的74％发生在Ano Nuevo岛25公里以内，这表明捕食的相对敏感性使用Ano Nuevo岛的西方海鸥对岛的距离随距离的增加而减少。在白天，小嘴鸥的西部鸥数量最多（占检测的91％），而夜间则主要有幼年鲑科类鱼（占检测的65％）。西部海鸥与鲑鱼之间最大的重叠发生在黄昏，因此迁徙鲑鱼的捕食可能是机会性的。当捕食者和猎物可能重叠时，阻止小河中的海鸥可能会缓冲从捕食中移出的鲑鱼。我们的结果将为管理策略提供信息，以最有效地减少海鸥捕食对加利福尼亚中部鲑鱼的影响。

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