Semester

Fall

Date of Graduation

2012

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Wildlife and Fisheries Resources

Committee Chair

Stuart A. Welsh

Committee Co-Chair

Patricia M. Mazik

Committee Member

David R. Smith

Abstract

This thesis examines habitat preference of yellow-phase American eels (Anguilla rostrata) and relationships between age and length with that preference. The thesis is comprised of two chapters: (1) an introduction and literature review on American eel life history, their habitat selection, and the study of resource selection, and (2) an experimental study of yellow-phase American eel habitat preference and relationships between preference and age and length. Given widespread habitat alteration of North American rivers, an understanding of the use and selection of habitat is important to conservation and management of the American eel. Yellow-phase American eels are often considered as habitat generalists, in part, because of their occurrence across a wide range of habitat types, but few experimental studies have examined microhabitat selection. In a laboratory experiment, I quantified microhabitat use of small yellow-phase American eels (n = 130, 224--338 mm TL) conditional on five benthic substrate types common to many rivers within the geographic range of the American eel. During nine, 4-day trials replicated with three aquaria, American eels were given a choice to burrow into five equally available benthic substrates: cobble (90--256 mm), gravel (4--16 mm), sand (0.125--1 mm), silt/clay (< 0.0625 mm), and leaf pack. Five American eels were used per aquaria for each trial, and individuals were used one time only. All eels were injected with PIT tags prior to the study, which allowed for determination of lengths and otolith-based ages of each individual following each trial. Leaf pack was selected with a significantly higher probability than other substrates (63 of 130 individuals). However, other substrates were also used (cobble, 21 of 130; silt/clay, 18 of 130; gravel, 16 of 130; and sand, 12 of 130). Length and age covariates were not associated with substrate selection. Selection of leaf pack habitat supports the importance of terrestrial organic material and riparian zones to yellow-phase American eels in riverine systems.

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