Trophic interactions, foodweb dynamics and ontogeny in juvenile Pacific salmon in lakes and coastal marine ecosystems

太平洋鲑鱼，被视为具有重大经济、社会和文化效益的前哨鱼种。具体而言，在了解淡水和海洋生态系统中幼太平洋鲑鱼的资源分配、营养相互作用和食物网动态方面存在重大差距。从我过去对阿拉斯加红鲑系统的研究中，我们发现，红鲑鱼苗在淡水湖泊中的生长和生存受到密度依赖和密度无关因素的影响，迁移到海洋的小鲑鱼的大小和年龄分布也是如此。然而，重要的进一步研究是必要的，以了解和量化的过程和机制，导致可变的大小和年龄结构的红鱼苗和小鲑鱼特定的湖泊系统。然而，实现这些目标由于沿海地区不断变化的气候状况（降水和温度）而变得更加复杂。进一步的复杂性是由于引进物种，如鲈鱼和鲈鱼到几个红眼湖在公元前，作为青少年可能有显着的生态位重叠与红眼鱼苗以及棘鱼，而作为成年人，他们成为捕食者的红眼鱼苗和棘鱼。这将是至关重要的，以确定这些变量的情况和相关的过程如何影响的大小和年龄分布的红鱼苗，他们的食物和喂养习惯，生态位的变化和营养相互作用与同居的鱼类和无脊椎动物的捕食者，以及这些如何影响他们的生长和生存，出迁移的大小和年龄的小鲑鱼，和他们的表现在早期的海洋生长。同样，其他太平洋鲑鱼物种的幼鱼的大小（例如，在不同年份和种群之间，进入海洋时，鳕鱼（coho）和奇努克（Chinook）的情况也有很大差异，这可能对它们在沿海海洋生态系统中早期生长期间的表现产生重大影响。随着幼鲑进入海洋，它们之间以及与其他饲料鱼类共享共同的觅食地和生态位，我的研究兴趣也将是了解物种内的个体发育生态位转移，物种间的生态位重叠，以及它们对海洋生长和生存的影响。以及它们与幼鲑营养相互作用和生长、沿水生食物网的能量和污染物转移、水生生物多样性和水质的联系，我将在未来5年继续沿着同一主题开展工作。本研究提出以下研究目标：1）检验不同密度的红鱼苗对低营养级幼鱼的结构和大小效率、红鱼苗的生长以及迁出幼鱼的大小和年龄结构的影响; 2）建立空间模型，（沿岸的与远洋的）红鱼苗的资源利用模式，以及在对比的捕食者-被捕食者情景下与同居食草动物的生态位重叠或缺乏; 3）测试引入的掠食性鱼类如何改变红鲑鱼苗的个体发育和迁出的小鲑鱼的相关人口统计学; 4）描述和模拟红鲑幼鱼和其他两种太平洋鲑鱼的食物网（coho和chinook）作为海洋入口和早期海洋生长期间大小的函数;和5）模型的空间（岸上与离岸）和时间（年际）变化的营养位置，资源分配和个体发育生态位的变化，在幼年太平洋鲑鱼作为大小的函数。大约6-8名研究生和10-12名本科生将通过拟议的研究项目进行培训，这些项目将产生至关重要的新知识，以了解与幼年太平洋鲑鱼高度可变的表现有关的过程。

Pacific salmon, regarded as sentinel species with significant economic, social and cultural benefits. Specifically, there are major gaps in understanding resource partitioning, trophic interactions and foodweb dynamics of juvenile Pacific salmon in freshwater and marine ecosystems. From my past research on sockeye systems in Alaska, we found that the growth and survival of sockeye fry in freshwater lakes are affected by both density dependent and density independent factors, as do the size and age distribution of smolts migrating to ocean. However, significant further research is needed to understand and quantify the processes and mechanisms leading to variable size- and age-structure of sockeye fry and smolts for specific lake systems. However, achieving these is further complicated by the shifting climate regimes (precipitation and temperature) in coastal region. Further complications are be due to introduced species like perch and bass to several of the sockeye lakes in BC, which as juveniles may have significant niche overlaps with sockeye fry as well as stickleback, while as adults they become predators of sockeye fry and stickleback. It would be fundamentally importance to determine how these variable scenarios and the associated processes influence the size- and age-distribution of sockeye fry, their food and feeding habits, niche shifts and their trophic interactions with cohabiting fish and invertebrate predators, and how these affect their growth and survival, out-migrating size and ages of smolt, and their performance during early marine growth. Similarly, the sizes of the juveniles of other Pacific salmon species (e.g., coho and Chinook) at ocean entry also vary greatly between years and among stocks, which may have significant implications for their performance during their early growth in the coastal marine ecosystems. As the juvenile salmon enter the ocean, they share common feeding grounds and niches among themselves and with other forage fish species, my research interest will also be to understand the ontogenetic niche shifts within species, niche overlaps among species, and their implications for ocean growth and survival.In line with my long-term research goals of looking at the patterns of nutrient-foodweb dynamics of aquatic systems, and their links with trophic interactions and growth of juvenile salmon, energy and contaminant transfer along aquatic foodweb, planktonic biodiversity and water quality, I will continue along the same theme during the next 5 years. I propose the following research objectives: 1) test how the variable density of sockeye fry modifies the structure and size-based efficiency of lower trophic levels, growth of sockeye fry and size and age structure of out-migrating smolts; 2) model spatial (littoral versus pelagic) patterns of resource utilization by sockeye fry and niche overlaps or lack there of with cohabiting planktivores under contrasting predator-prey scenarios; 3) test how the introduced predatory fish species shift ontogeny of sockeye fry and associated demography of out-migrating smolts; 4) characterize and model the foodwebs of juvenile sockeye and two other Pacific salmon species (coho and chinook) as a function of size at ocean entry and during early marine growth; and 5) model spatial (onshore vs. offshore) and temporal (inter-annual) variation in trophic position, resource allocation and ontogenetic niche shifts in juvenile Pacific salmon as a function of size. About 6-8 graduate students and 10-12 undergraduate students will be trained through proposed research projects that will generate fundamentally important and new knowledge towards understanding of the processes linked with highly variable performances of juvenile Pacific salmon.