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首页> 外文期刊>Ecology letters >Density-dependent mortality in Pacific salmon: the ghost of impacts past?
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Density-dependent mortality in Pacific salmon: the ghost of impacts past?

机译：太平洋鲑鱼的密度依赖性死亡率：过去的影响的幽灵？

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摘要

Conservation biologists often ignore density dependence because at-risk populations are typically small relative to historical levels. However, if populations are reduced as a result of impacts that lower carrying capacity, then density-dependent mortality may exist at low population abundances. However, we explore this issue in threatened populations of juvenile chinook salmon (Oncorbyncbus tsbawytscba). We followed the fate of more than 50 000 juvenile chinook in the Snake River Basin, USA to test the hypothesis that their survival was inversely associated with juvenile density. We also test the hypothesis that their survival was inversely associated with juvenile density. We also tested the hypotheses that non-indigenous brook trout and habitat quality affect the presence or strength of density dependence. Our results indicate that juvenile chinook suffer density-dependent mortality and the strength of density dependence was greater in streams in which brook trout were absent. We were unable to detect an effect of habitat quality on the strength of density dependence. Historical impacts of humans have greatly reduced population sizes of salmon, and the density dependence we report may stem from a shortage of nutrients normally derived from decomposing salmon carcasses. Cohorts of juvenile salmon may experience density-dependent mortality at population sizes far below historical levels and recovery of imperiled populations may be much slower than currently expected.
机译：保护生物学家经常忽略密度依赖性，因为相对于历史水平，处于危险中的种群通常很小。但是，如果由于承载力降低而导致人口减少，那么人口密度较低时可能会存在密度依赖性死亡率。但是，我们在濒临灭绝的奇努克鲑（Oncorbyncbus tsbawytscba）种群中探索了这个问题。我们追踪了美国蛇河盆地5万多名少年契努克族的命运，以检验其生存与少年密度成反比的假说。我们还检验了其生存与少年密度成反比的假设。我们还检验了非本地河鳟和栖息地质量影响密度依赖的存在或强度的假设。我们的结果表明，在没有溪鳟鱼的溪流中，幼稚的奇努克人的死亡率取决于密度，强度的强度更大。我们无法检测到栖息地质量对密度依赖性强度的影响。人类的历史影响极大地减少了鲑鱼的种群规模，我们报告的密度依赖性可能源于通常分解鲑鱼尸体而产生的营养物质的短缺。幼鲑种群在远低于历史水平的种群规模下可能会经历密度依赖的死亡率，受灾种群的恢复可能比目前预期的慢得多。

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