Department of Biology, Dalhousie University, Halifax, NS, B3H4J1 Canada.
J Fish Biol. 2012 Oct;81(5):1626-45. doi: 10.1111/j.1095-8649.2012.03419.x.
To estimate mortality rates, assess the spatio-temporal dynamics of natural mortality and examine migratory behaviour during the fresh to saltwater transition, 185 wild Atlantic salmon Salmo salar smolts were implanted with coded acoustic transmitters. Seaward migration of tagged S. salar from four river systems in an area of Nova Scotia, Canada known as the Southern Upland was monitored using fixed receivers and active telemetry over 3 years. Cumulative survival through the river, inner estuary, outer estuary and bay habitats averaged 59·6% (range = 39·4-73·5%). When standardized to distance travelled, survival rates followed two patterns: (1) constant rates of survival independent of habitat or (2) low survival most frequently associated with inner estuary habitats. In rivers where survival was independent of habitat, residency periods were also independent of habitat, post-smolts exhibited few upstream movements, took a more direct route to the ocean and reached the ocean rapidly. Alternatively, in rivers where survival was habitat specific, residency was also habitat specific with overall increased residency, more frequent upstream movements and delayed arrival to the open ocean. The sudden disappearance of most (75-100%) smolts and post-smolts assumed dead during the course of this study warrants further examination into the role of avian predators as a mortality vector.
为了估算死亡率，评估自然死亡率的时空动态，并研究从淡水到咸水过渡期间的洄游行为，我们为 185 条野生大西洋鲑鱼（Salmo salar）幼鱼植入了编码声纳发射器。在加拿大新斯科舍省一个名为“南部高地”的地区，我们使用固定接收器和主动遥测技术，对来自四个河流系统的标记鲑鱼的向海洄游进行了三年的监测。通过河流、内港、外港和海湾栖息地的总存活率平均为 59.6%（范围为 39.4-73.5%）。当按照旅行距离标准化时，存活率遵循两种模式：（1）独立于栖息地的恒定存活率；（2）与内港栖息地最相关的低存活率。在那些存活率与栖息地无关的河流中，居留期也与栖息地无关，幼鱼很少有向上游的运动，采取更直接的路线进入海洋，并迅速到达海洋。相反，在那些存活率与栖息地相关的河流中，居留期也是特定于栖息地的，整体居留期延长，向上游的运动更加频繁，到达开阔海域的时间也延迟了。在这项研究过程中，大多数（75-100%）幼鱼和幼鲑鱼突然消失，假设已经死亡，这需要进一步研究鸟类捕食者作为一种死亡因素的作用。
