Wilson Samantha M, Robinson Kendra A, Gutzmann Sarah, Moore Jonathan W, Patterson David A
Earth to Ocean Research Group, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada.
Fisheries and Oceans Canada, Cooperative Resource Management Institute, School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
Conserv Physiol. 2021 Mar 24;9(1):coab014. doi: 10.1093/conphys/coab014. eCollection 2021.
Long-distance migrations can be energetically demanding and can represent phases of high mortality. Understanding relationships between body condition and migratory performance can help illuminate the challenges and vulnerabilities of migratory species. Juvenile anadromous sockeye salmon () may migrate over 1000 km from their freshwater nursery habitats to estuary and ocean feeding grounds. During the period corresponding to the seaward migration of sockeye salmon, we held smolts in the laboratory to ask the following: (i) Does non-feeding migration duration influence prolonged swim performance and survival? (ii) What are the relationships between individual body condition and swim performance and survival? Wild sockeye salmon were intercepted during their migration and held without food for up to 61 days to represent the non-feeding freshwater migration and the extremes of poor estuary habitat. We conducted 40 sets of prolonged swim trials on 319 fish from 3 treatment groups that represented entrance to the marine environment on (i) an average,(ii) a delayed and (iii) a severely delayed migration schedule. Experimentally controlled freshwater migration duration did not impact swim performance or survival. Swim performance decreased concomitant with condition factor, where smolts with a Fulton's condition factor of <0.69 were less likely (<50% probability) to complete the swim test (90 min swim test, at ~0.50 m/s). Survival of salmon smolts in the laboratory was less likely at energy densities of less than 3.47 MJ/kg. Swim performance decreased much sooner than survival, suggesting that swim performance, and therefore condition factor, may be a good indicator of survival of migratory smolts, as fish with reduced swim performance will likely be predated. These two relationships, one more ecologically relevant and one more clinical, help reveal the limits of long-distance migration for juvenile salmon and can be used to determine population-specific starvation risk associated with various freshwater and marine habitat conditions.
长途迁徙对能量的需求很大，可能代表着高死亡率阶段。了解身体状况与迁徙表现之间的关系有助于阐明迁徙物种面临的挑战和脆弱性。幼年溯河产卵红大马哈鱼可能会从它们的淡水育苗栖息地洄游超过1000公里，到达河口和海洋觅食地。在红大马哈鱼向海洄游的对应时期，我们在实验室中饲养幼鱼，以探讨以下问题：（i）不进食的迁徙持续时间是否会影响长时间游泳表现和存活率？（ii）个体身体状况与游泳表现及存活率之间有什么关系？野生红大马哈鱼在洄游期间被拦截，并在不喂食的情况下饲养长达61天，以模拟不进食的淡水洄游以及河口恶劣栖息地的极端情况。我们对来自3个处理组的319条鱼进行了40组长时间游泳试验，这3个处理组分别代表了（i）平均、（ii）延迟和（iii）严重延迟的洄游时间表进入海洋环境的情况。实验控制的淡水迁徙持续时间并未影响游泳表现或存活率。游泳表现随条件因子下降，当富尔顿条件因子<0.69的幼鱼完成游泳测试（90分钟游泳测试，速度约为0.50米/秒）的可能性较小（<50%概率）。当能量密度低于3.47兆焦/千克时，实验室中鲑鱼幼鱼的存活率较低。游泳表现比存活率下降得更早，这表明游泳表现，进而条件因子，可能是洄游幼鱼存活率的良好指标，因为游泳表现下降的鱼可能更容易被捕食。这两种关系，一种更具生态相关性，一种更具临床相关性，有助于揭示幼年鲑鱼长途迁徙的极限，并可用于确定与各种淡水和海洋栖息地条件相关的特定种群饥饿风险。
