Andersson Magdalena, Jonsson Bror, Calles Olle, Greenberg Larry
River Ecology and Management Research Group, Department of Environmental and Life Sciences, Karlstad University, 651 88 Karlstad, Sweden.
Norwegian Institute for Nature Research, 0855 Oslo, Norway.
Animals (Basel). 2024 Jul 20;14(14):2116. doi: 10.3390/ani14142116.
By analyzing otolith microchemistry, we examined the use of freshwater and marine environments by brown trout L. that spawn in the Swedish River Emån and migrate to the Baltic Sea. We estimated the time juveniles spent in freshwater and the number of times the fish returned to freshwater, presumably to spawn. Twenty-six percent of the fish migrated to sea by 1 year of age. However, 13% spent less than one year in the river. Most brown trout (48%) migrated to the sea between 1 and 2 years of age. On average, brown trout, which averaged 4.4 years in age (range 3-6 years), returned to freshwater 2.3 times, and there was an inverse relationship between time spent in freshwater after hatching and the number of visits to freshwater. Our results do not support the classical life history pattern, where brown trout spend one or more years in freshwater before migrating to the sea. Here, we found evidence that part of the population leaves freshwater during their first year. While the cause for precocial migration in the River Emån is not known, our results from this permanently flowing river do not support the idea proposed for other Baltic Sea populations, where the risk of drought has been suggested to be the cause.
通过分析耳石微化学，我们研究了在瑞典埃曼河产卵并洄游至波罗的海的褐鳟对淡水和海洋环境的利用情况。我们估算了幼鱼在淡水中度过的时间以及鱼类返回淡水（推测是为了产卵）的次数。26%的鱼在1岁时洄游至大海。然而，13%的鱼在河中停留的时间不到一年。大多数褐鳟（48%）在1至2岁之间洄游至大海。平均而言，年龄在4.4岁（范围为3至6岁）的褐鳟返回淡水2.3次，并且孵化后在淡水中度过的时间与返回淡水的次数之间存在负相关关系。我们的研究结果不支持经典的生活史模式，即褐鳟在洄游至大海之前在淡水中度过一年或多年。在此，我们发现有证据表明部分种群在第一年就离开淡水。虽然埃曼河早熟洄游的原因尚不清楚，但我们在这条常年流水的河流中得到的结果并不支持针对其他波罗的海种群所提出的观点，即干旱风险被认为是其原因。
