Sea-run brown trout (Salmo trutta) have a highly phenotypically plastic life history that allows them to be effective colonizers and competitors in freshwater. This paper documents a previously unknown spawning behaviour in a brackish, tidally influenced estuary 14 km from the mouth of the Vosso River, a major Atlantic salmon- and sea-run brown trout–producing river in western Norway. Putative spawning gravel was observed, and sea-run brown trout deposited eggs that hatched in April. Survival of recruits was high (> 95%) in the tidal spawning gravel. These areas are strongly tidally influenced with a peak of 23.17 psu recorded at the lowest spawning ground. The observation of spawning so far from the river mouth may be unique in such a system with a long estuary but provides important insight into the biology of sea trout. Invasion of pink salmon, also known to spawn in estuaries, may negatively affect the competitive balance of sea trout with other salmonids in rivers where sea trout populations rely on recruitment from these relatively extreme spawning areas. Restoration of estuaries that have been modified by dredging or channelization may be important to ensure quality and heterogenous habitat for sea trout spawning given that haline spawning grounds could contribute to population resilience.

海产褐鳟（Salmo trutta) 具有高度表型可塑性的生活史，使它们能够成为淡水中有效的殖民者和竞争者。本文记录了在距挪威西部一条主要的大西洋鲑鱼和海产褐鳟鱼生产河流 Vosso 河口 14 公里处受潮汐影响的咸淡水河口中的一种先前未知的产卵行为。观察到推定的产卵砾石，海中褐鳟产卵于 4 月孵化。在潮汐产卵砾石中，新兵的存活率很高（> 95%）。这些区域受到潮汐的强烈影响，在最低产卵场记录的峰值为 23.17 psu。在这样一个河口很长的系统中，对距河口这么远的产卵的观察可能是独一无二的，但提供了对海鳟生物学的重要见解。粉红鲑鱼的入侵，也已知在河口产卵，可能会对海鳟鱼与河流中其他鲑鱼的竞争平衡产生负面影响，在这些河流中，海鳟鱼种群依赖于这些相对极端的产卵区的补充。鉴于盐碱产卵场有助于提高种群恢复能力，恢复因疏浚或渠道化而改变的河口对于确保海鳟产卵的质量和异质栖息地可能很重要。