ABSTRACT: The sea trout (anadromous brown trout Salmo trutta) displays extensive among-individual variation in marine migration behaviour. We studied the migration behaviour of 286 sea trout (27-89 cm) tagged with acoustic transmitters in the spring, in 7 populations located in 2 distinct marine fjord systems in Norway. We examined whether individual nutritional state, sex and body size influenced marine migration behaviour in terms of (1) the decision to migrate to the sea or remain resident in freshwater and/or estuarine habitats, (2) seasonal timing of sea entry, (3) duration of the marine residency and (4) migration distance at sea from the home river. Most sea trout were in a poor nutritional state in the spring prior to migration. Sea trout with low body condition factors and low plasma triglyceride levels were more likely to migrate to sea, and low triglyceride levels were also associated with earlier sea entry. Poor body condition also increased the probability of individuals remaining at sea longer and migrating further offshore compared to fish in better condition. Females were more likely to migrate to the sea than males. Larger fish were also more likely to migrate to the sea instead of remaining in freshwater and estuaries, and dispersed over greater distances from the river than smaller fish. In conclusion, this study documented general trends across multiple populations and showed that nutritional state, sex and body size influence important aspects of the marine migration behaviour of sea trout.

中文翻译：

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营养状态，性别和体重对鳟鱼海洋迁移行为的影响

摘要：海鳟鱼（褐鳟鳟））在海洋迁移行为中表现出广泛的个体差异。我们研究了春季用声发射器标记的286海鳟（27-89厘米）在挪威2个不同的海洋峡湾系统中的7个种群中的迁移行为。我们从以下方面检查了个人的营养状况，性别和体型是否影响了海洋迁移行为：（1）决定迁移到海中还是继续居住在淡水和/或河口生境中；（2）入海季节的季节性；（3 ）海洋居住的持续时间，以及（4）海上从母河迁移的距离。在迁移之前的春季，大多数海鳟的营养状况很差。具有低身体状况因素和低血浆甘油三酸酯水平的海鳟更可能迁移到海中，低甘油三酯水平也与较早的入海有关。与状况较好的鱼类相比，较差的身体状况还增加了个体在海上停留时间更长并迁移到近海的可能性。女性比男性更可能迁移到海中。较大的鱼类也更可能迁移到海洋，而不是留在淡水和河口中，并且与较小的鱼类相比，与河流的距离更大。总之，本研究记录了多个人群的总体趋势，并表明营养状况，性别和体型影响着鳟鱼海洋迁移行为的重要方面。女性比男性更可能迁移到海中。较大的鱼类也更可能迁移到海洋，而不是留在淡水和河口中，并且与较小的鱼类相比，与河流的距离更大。总之，本研究记录了多个人群的总体趋势，并表明营养状况，性别和体型影响着鳟鱼海洋迁移行为的重要方面。女性比男性更可能迁移到海中。较大的鱼类也更可能迁移到海洋，而不是留在淡水和河口中，并且与较小的鱼类相比，与河流的距离更大。总之，本研究记录了多个人群的总体趋势，并表明营养状况，性别和体型影响着鳟鱼海洋迁移行为的重要方面。