Date of Award

12-2022

Access Control

Open Access

Degree Name

Biology, M.A.

Department

Biology Department

Advisor

Christopher Pennuto

Department Home page

Biology

First Reader

Christopher Pennuto

Second Reader

Randal Snyder

Third Reader

Robert Warren

Abstract

Seasonality, energy recruitment, and food web position dictate the degree of impact fish impose on their surrounding environment. In the Great Lakes, the round goby (Neogobius melanostomus) is known to out-migrate from nearshore habitat to offshore depths in the winter months. However, in Great Lake tributaries, round goby populations were found up to 25 km upstream during winter months, and distance upstream was a predictor of out-migration propensity; populations farthest upstream did not out-migrate. Seasonal resources shaped the diet and condition of these fish thus creating inland populations with different average lengths, diets, and body condition compared to one another. In some streams, round goby winter diets consisted of net-spinning caddis flies and amphipods whereas in others they primarily selected chironomid larvae.

Across seasons, in-situ round goby foraging impacted upstream-downstream energy connections by reducing midge abundance in drift and affecting amphipod benthic abundance. In artificial stream mesocosm trials, round goby reduced amphipod diel drift through behavior cues and predation. Since round goby are known to consume pre-emergent taxa such as larval caddis, chironomids, and mayflies, this potentially allows them to impact stream-to-riparian resource linkages. Riparian predator abundance was found to be impacted by the amount of pre-emergent taxa in drift, however, round goby presence alone was not found to impair this resource pathway.

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