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首页> 外文期刊>North American Journal of Fisheries Management >Predation on Juvenile Pacific Salmon Oncorhynchus spp. in Downstream Migrant Traps in Prairie Creek, California
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Predation on Juvenile Pacific Salmon Oncorhynchus spp. in Downstream Migrant Traps in Prairie Creek, California

机译：对太平洋幼鲑Oncorhynchus spp的捕食。在加利福尼亚大草原溪的下游移民陷阱中

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摘要

Downstream migrant traps are a widely applied fishery management tool for sampling anadromous Pacific salmon Oncorhynchus spp. and steelhead O. mykiss smolts along the West Coast of North America and elsewhere, yet predation on juvenile salmonids in traps has not been studied quantitatively. We assessed the frequency of occurrence and abundance of juvenile salmonids in the stomachs of coastal cutthroat trout O. clarkii clarkii, coho salmon O. kisutch, steelhead, and prickly sculpin Cottus asper (> 70 mm fork length) captured in traps and in nearby stream habitats. All four predator species took juvenile salmonids with much greater frequency in traps than in stream habitats. Among free-swimming predators, only coastal cutthroat trout were observed with salmonid fry in their stomachs, but they took fewer salmonid prey and appeared to rely more heavily on insect prey than did coastal cutthroat trout captured in traps. Predators consumed up to 25% of the available prey over a broad range of prey abundances. Over the course of the study, predators consumed 2.5% of all salmonid fry captured in traps, but this fraction ranged from less than 1% to more than 10% in any given year. The number of prey taken in traps increased with predator length and with prey abundance in traps, and predation in traps peaked during the period of most intense downstream migration by salmon fry. In contrast, live-box design and trap location had little or no effect on the total number of prey taken by individual predators. We estimated that the predation mortality of juvenile salmon increased by 0.5-1.0% due to in-trap predation (i.e., a 9-10% relative increase over natural predation rates). We found no evidence that predators selected for prey on the basis of species. These results should motivate additional research on methods that reduce or eliminate predation in trap live-boxes and protocols for efficiently measuring predation associated with the trapping of downstream migrants.
机译：下游移民诱捕器是一种广泛使用的渔业管理工具，用于抽样采集太平洋鲑鱼Oncorhynchus spp。和北美北部西海岸和其他地方的顽皮红头鲷（O. mykiss）熏鲑，但是尚未对捕集器中幼鲑的捕食进行定量研究。我们评估了在沿海割喉鳟鱼O. clarkii clarkii，银大麻哈鱼O. kisutch，硬皮鱼和多刺的Cottus asper（> 70 mm叉长）的胃中捕获和捕获的捕捞陷阱和附近溪流中幼鲑鱼的发生频率和丰度。栖息地。所有四种捕食者在陷阱中捕捞的幼鲑鱼的频率均比在河流栖息地中的捕捞频率高得多。在自由游动的捕食者中，仅观察到沿海凶猛鳟鱼的肚子里夹着鲑鱼苗，但是与捕获在陷阱中的沿海凶猛鳟鱼相比，它们捕食的鲑鱼猎物更少，并且对昆虫的猎物的依赖程度更高。捕食者在各种各样的猎物丰富度中消耗了多达25％的可用猎物。在整个研究过程中，捕食者消耗了捕捞阱中捕获的所有鲑鱼苗的2.5％，但是在任何给定年份中，这一比例范围从不到1％到超过10％。捕食者捕获的猎物数量随着捕食者的长度和捕食者丰富度的增加而增加，并且在鲑鱼苗向下游的最强烈迁移期间捕捕者捕食达到高峰。相反，活体箱的设计和诱捕器的位置对单个捕食者捕食的猎物总数几乎没有影响。我们估计，由于圈内捕捞，幼鲑的捕食死亡率提高了0.5-1.0％（即比自然捕捞率高9-10％）。我们没有发现证据表明掠食者是根据物种选择猎物的。这些结果应促使人们对减少或消除陷阱活箱中捕食的方法和有效测量与下游移民被捕有关的捕食的规程进行进一步研究。

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