AWRI Newsletter #62: March 2007

Matt Breen, a graduate student at the Annis Water Resources Institute working under the direction of Dr. Carl Ruetz, is studying the movement patterns, habitat use, and feeding ecology of mottled sculpins (Cottus bairdii) in a small stream in Calhoun County. Mottled sculpins are small, non-game fish that live on the bottom of many coldwater streams. Mottled sculpins are important components of stream ecosystems because they are often the most abundant fish species in coldwater streams and they function both as predators on aquatic invertebrates and prey for larger trout. Nevertheless, mottled sculpins are often overlooked because of their small size and their camouflage coloration that can cause them to go unnoticed by the untrained eye. Matt's research aims to provide important ecological information on this often overlooked component of stream ecosystems. Matt's research is partially supported by grants from the Kalamazoo Chapter of Trout Unlimited and Grand Valley State University.

To study fish movement, Matt injected small tags-known as passive integrated transponders (PIT)-into the body cavities of sculpins. PIT-tagged fish emit a unique code that identifies them when scanned by a hand-held underwater antenna. The advantage of using PIT tags is that tagged fish can be relocated in the stream without having to be physically captured. This past summer and winter-through sun, rain, and snow-Matt tracked the movements of sculpins during day and night. He also examined what sculpins ate relative to the availability of prey in different habitats in the stream, hypothesizing that sculpin movement patterns are closely tied to prey availability.

Matt's research suggests that PIT tags provide an excellent approach for tracking sculpin movements. His preliminary results suggest that sculpins moved more during summer than winter. Additionally, Matt found that sculpins may move much farther than previously reported. Matt is anxious to continue his analyses to determine whether food availability can be used to better explain movement patterns and habitat use at a variety of spatial scales.

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