Anadromous Pacific salmon are semelparous, and resource subsidies from spawning adults (marine-derived nutrients, or MDN) benefit juvenile salmonids rearing in freshwater. However, it remains unclear how MDN assimilation relates to spawner abundance within a watershed. To address this, we examined seasonal, watershed-scale patterns of MDN assimilation in rearing coho (Oncorhynchus kisutch) and Chinook (O. tshawytscha) salmon and compared it with spawner biomass and landscape features in a western Alaska watershed with contrasting structural complexity in two sub-drainages. Adult salmon biomass density was estimated from escapement and spawner distribution data, and MDN assimilation in juvenile salmon was estimated via stable isotopes. In the North River, MDN assimilation was lowest in early summer, prior to annual spawning migrations, increased after spawning, and peaked in late winter. In the more complex mainstem Unalakleet River, MDN assimilation was higher but varied minimally from summer through fall before increasing in late fall and winter. Summer MDN assimilation, prior to salmon spawning, was primarily a function of habitat complexity, where MDN was highest in sloughs and the more complex mainstem river. After salmon spawned, fall MDN assimilation was a function of adult pink and Chinook salmon biomass as well as MDN assimilation that occurred prior to spawning (that is, summer MDN), but unrelated to total summer biomass (all salmon species biomass combined). Thus, MDN assimilation by juvenile salmon in the fall was a function of species-specific adult spawner abundance but seasonal patterns of MDN assimilation were masked in complex habitat where summer MDN assimilation remained high.

太平洋淡水鲑鱼是互生的，产卵成年的资源补贴（海洋来源的养分或MDN）有利于淡水中饲养的幼鲑鱼。但是，尚不清楚MDN同化与分水岭内产卵数量的关系。为了解决这个问题，我们研究了饲养金枪鱼（Oncorhynchus kisutch）和奇努克（O. tshawytscha）的MDN同化的季节性，分水岭规模模式）鲑鱼，并将其与阿拉斯加西部流域的产卵生物量和景观特征进行了比较，对比了两个子流域的结构复杂性。根据逃逸和产卵场分布数据估算成年鲑的生物量密度，并通过稳定同位素估算幼鲑中的MDN同化率。在北河，MDN的同化作用在夏季每年产卵迁移之前的初夏最低，在产卵后增加，在冬季末达到顶峰。在更复杂的主干河Unalakleet河中，MDN的同化度较高，但从夏季到秋季变化最小，而在秋末和冬季则有所增加。在鲑鱼产卵之前，夏季MDN的吸收主要取决于栖息地的复杂性，在泥沼和更复杂的主干河中，MDN最高。鲑鱼产卵后 秋季MDN同化是成年粉红色和奇努克鲑鱼生物量以及产卵前（即夏季MDN）发生的MDN同化的函数，但与总夏季生物量（所有鲑鱼物种生物量的总和）无关。因此，秋天鲑鱼对MDN的吸收是特定物种成年产卵动物数量的函数，但在夏季MDN吸收仍然很高的复杂栖息地中，MDN吸收的季节性模式被掩盖了。