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Access Type

Open Access Thesis

Document Type


Degree Program

Environmental Conservation

Degree Type

Master of Science (M.S.)

Year Degree Awarded


Month Degree Awarded



The use of genetic markers in monitoring populations has become increasingly important for conservation purposes, and can take many forms. While effective population size (Ne) is of great interest to conservation genetics, it may be much easier and more practical to estimate the effective number of breeders (Nb) per cohort as a tool for genetic monitoring of populations. Few studies have estimated Nb for the same species over long periods of time in comparison with demographic or environmental variables. I estimated Nb of the eastern brook trout, Salvelinus fontinalis, as part of long-term studies of two stream systems: West Brook (WB) in Massachusetts and Stanley Brook (SB) in Maine. I used eight microsatellite loci for all available young of the year (YOY) from each cohort in WB and a random subset of YOY distributed evenly throughout SB to obtain genetic-based estimates. I estimated adult abundance (NC) from mark-recapture data, and used seasonal stream flow as an environmental variable. I performed linear models with Nb as the response variable and family structure (number of families and variance in family size), NC, and seasonal stream flow as predictor variables. I found that both the number of families and variance in family size had a strong influence on Nb. Compared to abundance of adults and YOY, Nb was relatively stable over time.Stream flow in both autumn and spring showed a quadratic relationship with Nb in WB, suggesting that intermediate flows are optimal for maintaining a higher Nb. SB, with fewer years of data, did not show these relationships. If incorporated into monitoring programs, Nb can be a useful tool for detecting changes in population status and for informing management decisions.


First Advisor

Andrew Whiteley