Habitat effects on stream productive capacity, energy flow, and adaptive tradeoffs among juvenile salmonids

鱼类成功开发溪流栖息地的能力取决于自然栖息地结构、猎物产量以及捕食者和竞争对手的丰度。这些特征形成了鲑鱼和鲑鱼等漂流摄食性鱼类的适应环境，同时限制了能量转移到鱼类营养水平。与水化学和温度一样，物理生境结构(如河道形状、流速、底物)仍然是河流生产能力的最基本决定因素，了解鱼类生产的物理限制是预测生境变化对鱼类种群影响的关键。 该建议的目的是：1)建立一个与无脊椎动物漂流和漂流食性鲑鱼幼鱼(即太平洋鲑鱼和鲑鱼)的生产有关的一般过程模式；2)建立一个河流生境结构和流量对溪流鲑鱼产量影响的量化框架；2)在实验上确定在不同分类水平上区分幼鲑鱼的适应权衡，特别强调了解生长分化的作用；3)评估草食性鱼类分布的纬度限制是否影响其他功能性投喂鱼类，特别是漂流食性鱼类(如幼鲑鱼)的能量流动和产量。 这项研究将提供：1)栖息地对无脊椎动物漂流和幼体鲑鱼携带能力的生产和建模的新综合；2)河流径流科学在模型开发、验证和经验径流阈值确定方面的重大进展；3)更好地理解允许生境分区和沿环境梯度共存的适应性权衡的生理学基础；以及4)对溪流(草食动物)营养结构中大规模纬向倾斜的普遍性、根本原因和后果进行评估。这些是对河流、生物和群落生态学基本问题的重要贡献，并将直接应用于改善加拿大濒危鱼类物种的管理、河流径流和栖息地恢复，潜在影响范围从当地(濒危物种)到全球(改进的河流径流模拟技术)。

The ability of fish to successfully exploit stream habitats depends on physical habitat structure, prey production, and the abundance of predators and competitors. These features form the adaptive landscape for drift-feeding fish like salmon and trout, while simultaneously constraining energy transfer to the fish trophic level. Along with water chemistry and temperature, physical habitat structure (e.g. channel form, velocity, substrate) remains the most fundamental determinant of stream productive capacity, and understanding physical constraints on fish production is key to predicting the effects of habitat change on fish populations. The objectives of this proposal are i) to develop a general process model relating production of invertebrate drift and juvenile drift-feeding salmonids (i.e. Pacific salmon and trout) to stream habitat structure and discharge, as a quantitative framework for modeling habitat and flow effects on juvenile salmonid production in streams; ii) to experimentally determine the adaptive tradeoffs differentiating juvenile salmonids at different taxonomic levels, with a particular emphasis on understanding the role of growth differentiation; and iii) to evaluate whether latitudinal constraints on herbivorous fish distribution affect energy flow and production of other functional feeding groups of fish, particularly drift-feeding fish (e.g., juvenile salmonids). This research will provide i) a novel synthesis of habitat effects on production and modeling of invertebrate drift and juvenile salmonid carrying capacity; ii) significant advances in instream flow science, both in terms of model development, validation, and identification of empirical flow thresholds; iii) improved understanding of the physiological basis of adaptive tradeoffs that allow habitat partitioning and co-existence along environmental gradients; and iv) an assessment of the generality, underlying causation, and consequences of large-scale latitudinal clines in stream (herbivore) trophic structure. These represent important contributions to fundamental issues in stream, organismal, and community ecology, and will provide direct application to improving management of endangered fish species, instream flows, and habitat restoration in Canada, with potential impacts ranging from local (endangered species) to global (improved instream flow modeling techniques).