Norwegian Institute for Nature Research, Gaustadalléen 21, Oslo, Norway.
J Fish Biol. 2009 Feb;74(3):621-38. doi: 10.1111/j.1095-8649.2008.02152.x.
The aim of the paper was to study sea migration, growth and survival of brown trout Salmo trutta of the River Imsa, 1976-2005. The migratory S. trutta were individually tagged and fish leaving or entering the river were monitored daily in traps located near the river mouth. The mean annual duration of the sea sojourn was 6-9 months for first-time migrants moving to sea between January and June. It was 8-18 months for those migrating to sea between July and December. Veteran migrants stayed 12 months or less at sea and most returned to the river in August. Early ascending fish stayed the longest in fresh water because most returned to sea in April to May. The day number of 50% cumulative smolt descent correlated negatively with mean water temperature in February to March and the February North Atlantic Oscillation index (NAOI). Mean annual sea growth during the first 2 years after smolting was higher for S. trutta spending the winter at sea than those wintering in the River Imsa. First year's sea growth was lower for S. trutta descending in spring than autumn. For first-time migrants, it correlated negatively with the February NAOI of the smolt year. Sea survival was higher for spring than autumn descending first-time migratory S. trutta with a maximum in May (14.9%). Number of anadromous S. trutta returning to the river increased linearly with the size of the cohort moving to sea, with no evidence of density-dependent sea mortality. Sea survival of S. trutta smolts moving to sea between January and June correlated positively both with the annual number of Atlantic Salmo salar smolts, the specific growth rate at sea, and time of seaward migration in spring. This is the first study indicating how environmental factors at the time of seaward migration influence the sea survival of S. trutta.
本文旨在研究伊姆斯河 1976-2005 年褐鳟的海洋洄游、生长和存活情况。洄游的褐鳟被单独标记，每天在位于河口附近的陷阱中监测进出河流的鱼类。1 月至 6 月间首次洄游到海洋的幼鱼，其平均海洋逗留时间为 6-9 个月；7 月至 12 月间洄游到海洋的幼鱼，其平均海洋逗留时间为 8-18 个月。经验丰富的洄游幼鱼在海洋中的停留时间不超过 12 个月，且大多数于 8 月返回河流。早期溯河洄游的幼鱼在淡水中停留时间最长，因为大多数幼鱼于 4 月至 5 月返回海洋。50%累积幼鱼下溯天数与 2 月至 3 月的平均水温以及 2 月北大西洋涛动指数（NAOI）呈负相关。化育后前 2 年的平均年度海洋生长速度对于在海洋中越冬的褐鳟高于在伊姆斯河越冬的褐鳟。春季洄游的幼鱼比秋季洄游的幼鱼的第一年海洋生长速度低。对于首次洄游的幼鱼，其与化育年 2 月的 NAOI 呈负相关。春季首次洄游的幼鱼的洄游存活率高于秋季，最高可达 5 月（14.9%）。返回河流的洄游褐鳟数量与进入海洋的鱼群规模呈线性增长，且没有证据表明海洋死亡率与密度相关。1 月至 6 月间进入海洋的褐鳟幼鱼的洄游存活率与大西洋鲑鱼幼鱼的年数量、海洋生长速度以及春季向海洄游的时间均呈正相关。这是第一项表明海洋洄游时的环境因素如何影响褐鳟幼鱼洄游存活率的研究。
