Winter survival of stream salmonid fishes and implications for population dynamics

冬季被认为是北温带淡水鱼类生存的关键时期。相对较少的工作侧重于对存活率的直接估计，特别是对补充和鱼类种群动态的影响。为了估计冬季的存活率，计划了三个研究生项目。首先，我要回答的问题是“鸡蛋存活率是冬季严酷程度的函数吗？”在新不伦瑞克的各种溪流中，野生卵/羊驼的存活率将根据孵化环境的物理化学干扰(冰、溶解氧浓度)而确定。回答“冬季是种群生存的瓶颈吗？”第二个项目的重点将是野生大西洋幼鲑鱼(PARR)。在使用无源综合应答器(PIT)技术成功改进跟踪小型鱼类的基础上，具体目标将是通过在整个冬季和春季跟踪大河流范围内标记的PARR以及对冻结和洪水等干扰事件的反应，区分冬季死亡和PARR迁出。这些结果将成为模拟阶段间存活率的基础，以及环境和生物因素对驱动鲑鱼种群动态的相对重要性。 大西洋加拿大的气候变化情景预测冬季降雨量增加，冬季中期分裂事件的可能性更高。这样的变化可能会影响PARR的存活率。然而，还没有实验研究探讨冬季排泄事件与鲑鱼的身体状况(和生存)之间的关系。这是第三个项目的重点。利用室外水箱和模拟越冬“洪水”事件，将确定三个年龄级的未成熟和成熟的PARR的条件、能量含量、完成熏蒸的能力和存活率。拟议的研究具有强烈的保护重点，并试图确定自然环境应激源(冰、可变流量)的影响，特别是这些应激源可能会因气候变化情景(例如，冬季中期破裂)而加剧。这些结果应该会提高对环境因素和生物群之间关系的理解，以及我们保护处于危险中的人口的能力。

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.