Resource partitioning in the St. Lawrence estuary

这个NSERC支持的研究计划的长期目标一直是阐明如何高度异质性的环境，包围河口过渡区（淡水首先与海水混合）影响生态和河口鱼类的进化。我们建议实现四个主要目标。首先是评估开发过程中的河口景观产生的选择力，导致独立的表型轨迹的两个同域胡瓜在圣劳伦斯河口。我们将采样两个群体的胡瓜从孵化到繁殖（年龄3+），从而提供了一个纵向发展系列的增长，形态发育，生存和性成熟的深度，盐度和温度梯度沿着横向和纵向轴的函数。第二个具体的目标是测试的假设，小鳕，最丰富的鱼类的ETZ，形态专门利用深通道和浅水浅滩栖息地，并表现出形态的分歧相似的同域人群的胡瓜鱼。我们的第三个具体目标是利用这个相同的采样程序来描述整个鱼类群落的空间结构作为ETZ的物理梯度的函数。第四个具体目标是侧重于另一个工具，我们希望通过它来揭示空间和时间尺度上的资源分配。碳、氮和硫的稳定同位素分析将用于确定年度最佳鱼类和1+鱼类摄食的空间范围。同样的分层抽样计划涉及跨越ETZ环境梯度的30个站点的网格，将用于绘制所有关键过渡区鱼类所有生命史阶段的分布图。这些目标之所以能够实现，是因为有了一个新的取样平台（Lampsilis），可以对浅水和深水生境进行取样，并综合使用了包括稳定同位素分析和分子遗传学在内的创新技术。

The long term objective of this NSERC-supported research program has been to elucidate how the highly heterogeneous environments that characterise the estuarine transitional zone (where freshwater first mixes with seawater) influence the ecology and the evolution of estuarine fishes. We propose to pursue four major objectives. The first is to assess how the exploitation of the estuarine landscape during development generates the selective forces leading to independent phenotypic trajectories of two sympatric populations of smelt in the St. Lawrence estuary. We will sample two cohorts of smelt of both populations from hatching to reproduction (age 3+), thus providing a longitudinal developmental series for growth, morphological development, survival and sexual maturation as a function of depth, salinity and temperature gradients along transversal and longitudinal axes. The second specific objective is to test the hypothesis that tomcod, the most abundant fish of the ETZ, are morphologically specialized to exploit deep channel and shallow shoal habitat and exhibit a morphological divergence similar to that of the sympatric populations of smelt. Our third specific objective is to exploit this same sampling program to describe the spatial structure of the entire fish community as a function of the ETZ's physical gradients. The fourth specific objective is to focus on another tool with which we hope to reveal the partitioning of resources on a spatial and temporal scale. Stable isotope analyses of carbon, nitrogen and sulphur will be used to define the spatial extent of feeding of young-of-the-year and 1+ fishes. The same stratified sampling plan involving a grid of 30 stations spanning the environmental gradients of the ETZ will serve to map the distribution of all life history stages of all key transitional-zone fishes. These objectives are attainable thanks to the availability of a new sampling platform (the Lampsilis), which permits the sampling of shallow and deep-water habitat, and the use of a combination of innovative technologies including stable isotope analysis and molecular genetics.