Dissertation Research

Environmental and Social Effects of Water Management and Climate Change in the Ecuadorian Andes 

Governments around the world are increasingly challenged to provide reliable and affordable drinking water and hydropower to rapidly growing populations while ensuring that water usage does not degrade freshwater ecosystems or disrupt other ecosystem services. Freshwater resources will become increasingly valuable as increased demands create tension with decreasing supply due to glacier recession, drought, and other climate change effects. Understanding how aquatic biodiversity and function in rivers are affected by development and climate change is a primary concern of ecology and conservation science. My dissertation research aims to predict and map vulnerability of aquatic organisms and ecosystem function to human-induced changes across a latitudinal gradient and how these alterations affect rural communities that depend on streams and rivers in temperate and tropical regions.


Nutrient subsidy synergies between agriculture and stocked trout in freshwater streams

Migratory fish contribute to the structure and function of freshwater ecosystems through material ecosystem subsidies. Material subsidies occur when resources, such as energy and nutrients, are transferred between ecosystems. Each year, the New York State Department of Environmental Conservation (NYSDEC) stocks approximately 3.6 million trout and salmon, many of which are non-native, into almost 10,000 km of freshwater streams. Nearly 700,000 of these trout are stocked into streams within the Adirondack Park, thereby increasing areal density of trout in stocked sections and potentially representing an ecosystem nutrient subsidy. I am working to quantify stocked trout nutrient loads by combining nutrient recycling rate estimates with population density and biomass estimates. I then couple the nutrient input model estimates with measures of areal nutrient uptake in order to better understand the relative contribution of stocked hatchery trout to stream nutrient dynamics in nine streams along a gradient of agricultural land use across New York State . I am also working on estimating net flux of SDN in recipient streams using a mass-balance approach. This project is primarily funded through the Cornell College of Agriculture and Life Sciences Kieckhefer Adirondack Fellowship.


Modelling “true” survival: separating temporary and permanent emigration in estimates of surivorship

The focus of population ecology has largely shifted from estimating the size of a population to understanding the demographic mechanisms that control population size including reproduction, mortality, immigration, and emigration (Lebreton et al. 2009). Over the past few decades, advances in telemetry and tagging methods for studying fish movement in streams have shown that salmonids are much more mobile than previously thought, often showing a leptokurtic distribution of movement (Gowan et al. 1994). Separating emigration from estimates of survival rate is essential for understanding salmonid demographic processes in streams. The primary objective of this study is to use  multi-state mark recapture (MSMR) and robust design (RD) model frameworks to estimate “true” survival (i.e., not confounded with emigration and immigration) for three lotic salmonid species, native brook trout Salvelinus fontinalis and nonnative brown Salmo trutta and rainbow Onchorynchus mykiss trout. Furthermore, I will incorporate auxiliary habitat variables into our model, which will allow us to assess environmental factors that influence emigration and survival rates. Funding for Funding for this project is provided by the New York State Department of Environmental Conservation and the New York Cooperative Fish and Wildlife Research Unit.



Predicting stream carrying capacity for salmonids 

The New York Department of Environmental Conservation (NYSDEC) stocks trout in streams throughout the state to enhance and restore fisheries and provide fishing opportunities. The NYSDEC uses a suite of physical habitat and biological variables to estimate carrying capacity for streams that receive stockings. This capacity measure is incorporated into a Catch Rate Oriented Trout Stocking (CROTS) model for the annual allocation of stocked fish. A key assumption of the model is that there is sufficient carrying capacity to support stocked fish in streams during spring and summer months. If the carrying capacity of a stream is overestimated the stream may be stocked with too many fish, which could translate to reduced performance and survival and increased dispersal of wild and stocked salmonids, and may increase impacts on other native fish species. Conversely, under-stocking might result in unproductive fishery that is subject to overfishing on wild fish or reduced angler effort.  The relationship between the variables used in the carrying capacity model and suitability for trout growth and survival has not been evaluated quantitatively. I am working to estimate stream habitat carrying capacity for stocked and wild trout in nine study streams in New York State and using these models to predict maximum salmonid density. Funding for this project is provided by the New York State Department of Environmental Conservation and the New York Cooperative Fish and Wildlife Research Unit.

carmans map


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