Cooke Steven J, Hinch Scott G, Crossin Glenn T, Patterson David A, English Karl K, Healey Michael C, Shrimpton J Mark, Van Der Kraak Glen, Farrell Anthony P
Centre for Applied Conservation Research, Department of Forest Sciences, University of British Columbia, Vancouver, Canada.
Ecology. 2006 Jun;87(6):1575-86. doi: 10.1890/0012-9658(2006)87[1575:mboimi]2.0.co;2.
Reproductive-based migration is a challenging period for many animals, but particularly for Pacific salmonids, which must navigate from the high seas to freshwater natal streams. For the first time, we attempt to answer the question as to why some migratory adult Pacific salmon die en route to spawning grounds. Summer-run sockeye salmon (Oncorhynchus nerka) were used as a model, and the migration behavior of 301 fish was followed by intercepting them in the ocean about 215 km from the mouth of the Fraser River, British Columbia, Canada, and implanting a gastric radio transmitter. Before release, telemetered fish were also bio-sampled, which included drawing a blood sample, collecting a gill biopsy, and quantifying energetic status with a microwave energy meter. We tested the predictions that the fish that died prematurely would be characterized by low energy reserves, advanced reproductive development, elevated indicators of stress, and low osmoregulatory preparedness compared with fish that completed their river migration. Just over half (52.3%) of the sockeye tagged were subsequently detected in the Fraser River. Salmon that failed to enter the river had exhibited indicators of stress (e.g., elevated plasma lactate, glucose, and cortisol). Contrary to our prediction, fish that failed to enter the river tended to have higher gross somatic energy and be larger at the time of sampling in the ocean than fish that successfully entered the river. Of the fish that were detected in the river (i.e., 134 fish excluding fishery removals), 9.7% did not migrate beyond the lower reaches (approximately 250 km from ocean), and a further 14.2% reached the upper reaches but failed to reach natal sub-watersheds, whereas the remainder (76.1%) reached natal sub-watersheds. Of these, fish unsuccessful in the lower reaches tended to have a high plasma osmolality in the ocean, whereas fish failing in the upper reaches had lower levels of reproductive hormones in the ocean.
基于繁殖的洄游对许多动物来说都是一个具有挑战性的时期，对太平洋鲑科鱼类而言尤其如此，它们必须从公海洄游到淡水的出生地溪流。我们首次尝试回答为何一些洄游的成年太平洋鲑在前往产卵地的途中死亡这一问题。以夏季洄游的红大马哈鱼（Oncorhynchus nerka）作为模型，在加拿大不列颠哥伦比亚省弗雷泽河口约215公里处的海洋中拦截301条鱼，并植入胃内无线电发射器，以此追踪它们的洄游行为。在放生前，还对装有遥测设备的鱼进行了生物样本采集，包括采集血样、鳃活检样本，并用微波能量计量化能量状态。我们检验了以下预测：与完成河流洄游的鱼相比，过早死亡的鱼具有能量储备低、繁殖发育提前、应激指标升高和渗透调节准备不足的特征。随后在弗雷泽河中检测到刚超过一半（52.3%）被标记的红大马哈鱼。未能进入河流的鲑鱼表现出应激指标（如血浆乳酸、葡萄糖和皮质醇升高）。与我们的预测相反，未能进入河流的鱼在海洋采样时往往具有更高的总体体能，且体型更大。在河中被检测到的鱼（即134条鱼，不包括渔业捕捞的鱼）中，9.7%没有洄游到下游（距海洋约250公里处）以外，另有14.2%到达了上游但未能到达出生地子流域，而其余（76.1%）到达了出生地子流域。其中，在下游洄游失败的鱼在海洋中的血浆渗透压往往较高，而在上游洄游失败的鱼在海洋中的生殖激素水平较低。
