Document Type

Thesis

Date of Degree Completion

Spring 2008

Degree Name

Bachelor of Science

Department

Biology

Committee Chair

Dr. Paul W. James, Department of Biology

Second Committee Member

Dr. Andrew A. Piacsek, Science Honors Research Program Director

Abstract

The chiselmouth minnow (Acrocheilus alutaceus) is an herbivorous fish endemic to freshwater systems of the Pacific Northwest and abundant in mid-reaches of the Yakima River, WA. Uncommon in temperate streams, herbivorous fish are ecologically important because they provide a direct link between primary production and fish biomass. Chiselmouth minnows undergo ontogenetic morphological changes as they transform from insectivore to herbivore, the lower jaw becomes flattened, calcified and hardened for scraping algae and the intestine grows long for digestion. The timing of these changes in relation to diet and ecological status are poorly understood. By quantifying changes in jaw shape, intestine length and diet to fish size I chronologically describe changes to herbivory. This study shows as fish size increases, jaw curvature decreases and intestinal length increases. Analysis of stomach material suggests that herbivorous changes in diet occur before and more rapidly than adaptive morphological features.

Comments

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