Winter survival of stream salmonid fishes and implications for population dynamics

冬季被认为是北温带淡水鱼生存的关键时期。相对较少的工作集中于对生存的直接估计，特别是对补充和鱼类种群动态的影响。为了估计冬季生存能力，我们计划了三个研究生项目。首先，我提出了一个问题：“卵子的存活是否与严冬有关？”在新不伦瑞克省的各种溪流中，将根据孵育环境（redd）的物理-化学干扰（冰、溶解氧浓度）来确定野生卵/alevin的存活率。为了回答“冬季是种群生存的瓶颈吗？”这个问题，第二个项目的重点将放在野生幼年大西洋鲑鱼（parr）上。基于使用无源集成应答器（PIT）技术跟踪小型鱼类的成功改进，具体目标将是通过在整个冬季和春季以及响应冻结和洪水等干扰事件时跟踪大型河流中有PIT标记的鱼类来区分冬季死亡和洄游。这些结果将形成模拟阶段间生存的基础，以及驱动鲑鱼种群动态的环境和生物因素的相对重要性。

Winter is perceived as a critical period of survival for freshwater fishes in north temperate latitudes. Relatively little work has focused on direct estimates of survival and especially the influence on recruitment and fish population dynamics. To estimate winter survival, three graduate projects are planned. First, I address the question "Is egg survival a function of winter severity?" In various New Brunswick streams, wild egg/alevin survival will be determined in response to physico-chemical disturbance (ice, dissolved oxygen concentration) of the incubation environment (redd). To answer the question "Is winter a population survival bottleneck?" the focus of the second project will be on wild juvenile Atlantic salmon (parr). Based on successful modifications for tracking small fishes using passive integrated transponder (PIT) technology, the specific objective will be to distinguish between winter mortality and emigration of parr by tracking PIT-tagged parr in large river reaches throughout winter and spring and in response to disturbance events like freeze-up and flooding. These results will form the basis for modeling inter-stage survival and the relative importance of environmental and biological factors for driving salmon population dynamics. Climate change scenarios for Atlantic Canada predict increased winter precipitation, and a higher probability of mid-winter break-up events. Such changes may affect parr survival. However, no experimental studies have investigated the relationship between winter discharge events and body condition (and survival) of salmon parr. This is the focus of the third project. Using outdoor tanks and simulated 'flood' events over winter, the condition, energy content, ability to complete smoltification, and survival of three age-classes of immature and mature parr will be determined. The proposed research has a strong conservation focus and attempts to identify the effect of natural environmental stressors (ice, variable flows) especially as these stressors may be exacerbated by climate change scenarios (e.g., mid-winter break-ups). Results should improve understanding of the relationships between environmental factors and biota, and our ability to protect populations at risk.