Modeling the influence of channel morphology on spatial patterns in energetic profitability of foraging habitat for drift-feeding trout. (#22)
Channel morphology is a critical element of physical habitat for freshwater fish. The shape and roughness of channel bed and banks dictate the properties and spatial patterns of flow field, which in turn define hydraulic habitat that fish utilize for foraging, movement, spawning and refuge.
In this research, we have examined how channel morphology and the associated hydraulic conditions influence the distribution and energetic profitability of foraging habitat for drift-feeding salmonids. To this end, we have linked hydrodynamic and bioenergetic models and applied them to study habitat for cutthroat trout (Oncorhynchus clarkii clarkii) in four reaches of a small, mountain stream in British Columbia. These study reaches form a sequence of distinct channel morphologies ranging from cobble-bed rapid (plane-bed) to gravel-bed pool-riffle. The model was run for two flow scenarios, approximately 10% and 50% of the bankfull discharge. Using model output, we have investigated spatial patterns of net energy intake for three body size classes/age cohorts of trout within and between the study reaches.
Our results indicated existence of clear longitudinal and lateral patterns of net energy intake in all study reaches. The longitudinal variation in modeled energy intake were generally associated with morphological units while the lateral variation reflected primarily effects of bank roughness and large wood. Overall, study reaches with better developed bed topography (e.g. pool-riffle sequences) were predicted to provide higher quality foraging habitat during low flows. However, the model also suggested that during higher flows this pattern may no longer hold.