[PAST EVENT] Using geochemistry & genetics to determine the scale & ontogeny of fish dispersal in river networks

September 23, 2015
12pm - 1pm
VIMS - Watermen's Hall, Classroom A/B
1375 Greate Road
Gloucester Point, VA 23062Map this location
Fisheries Science Noon Seminar Series

Speaker: Dr. Robert Humston, Washington and Lee University

Title: Using geochemistry and genetics to determine the scale and ontogeny of fish dispersal in river networks

Abstract: Dispersal of stream fish between mainstem river and tributary habitats is central to connectivity of populations, expansion of invasive species, and spatial patterns in community composition across river-tributary networks. Using an approach combining geochemical isoscape modeling, otolith isotopic composition, and population genetics, we were able to determine the timing and scale of dispersal events across life history for smallmouth bass Micropterus dolomieu in the James River basin of Virginia. We used models incorporating major and minor geologic components and age of rock formation to predict strontium isotope ratios (87Sr/86Sr) in streams of the James River basin. Corresponding water sampling identified areas within the basin where tributaries were easily distinguished from mainstem habitats based on 87Sr/86Sr. We then applied this to reconstruct movement history of 220 individual fish. Results demonstrated that exchange between rivers is common; half of all fish analyzed moved between rivers at some point in their life. Most dispersed from their natal river in the first year of life within a few months post-spawn, revealing a much earlier and broader pattern of juvenile dispersal than previously described. There was no evidence for asymmetry of recruitment exchange between tributaries and mainstem, and no regular migratory movements were observed. Population genetic structure indicated isolation-by-distance within the mainstem and some spatial partitioning of genetic clusters, suggesting that longitudinal dispersal within mainstem habitats may be comparatively limited. Early juvenile dispersal appears to be a key driver of demographic exchange among habitats and should be an important consideration in spatial management strategies.

Biopic: I grew up waist deep in the waters around western New York chasing anything that swims. I went to Bowdoin College for my undergraduate degree and majored in Biology and English. After four years of bitter cold, I ran as far south as I could for graduate school in Marine Biology and Fisheries at University of Miami / RSMAS. I worked with Jerry Ault and Don Olson on coupling physical oceanographic models and remote sensing data with simulation models of fish movement behavior to analyze the spatial distribution of fish populations, including Bluefin tuna, spotted seatrout, and bonefish. I left Miami in 2001 and moved to to a postdoctoral position at Penn State University modeling the spatial ecology of invasive and agricultural pest weeds with David Mortensen and Ottar Bjornstad. I left PSU in 2003 and became an Assistant Professor in Biology at Virginia Military Institute where I started studying the ecology of stream fish populations. I moved to my current position at Washington and Lee University in 2008 where I am an Associate Professor in Biology and am currently the Associate Director of the Environmental Studies program. My research in Virginia focuses on the ecology of lotic recreational fisheries and implications of movement behavior for spatial population dynamics. Along the way I've also studied isotope geochemistry; human dimensions of water quality management in agricultural landscapes; ecology of Amazonian fisheries; genetics of threatened coral populations; stable isotope ecology; and whatever else I can get myself mixed up in.

[[v|mfabrizio,Professor Mary Fabrizio]]