Dietary Niche and Growth Rate of the Nonnative Tubenose Goby (Proterorhinus semilunaris)

Abstract

Basic life history knowledge is essential to determine if a nonnative species is potentially invasive. The nonnative tubenose goby (Proterorhinus semilunaris) arrived in the Great Lakes in the 1990s via ship ballast water, but remains poorly studied within North America, making it difficult to predict its effects on native ecosystems. Diet and growth patterns were examined from age-0 tubenose gobies within the estuary of the St. Louis River, a tributary to Lake Superior near Duluth, Minnesota. Dietary breadth and growth rates have important ramifications for survival, competitiveness, and dispersal ability of a fish species, influencing its potential success as an invasive species. I sampled tubenose gobies from shallow vegetated habitat via beach seine during summer and fall periods, and removed otoliths and aged fish on daily increments for growth modelling. Furthermore, stomach contents were identified and weighed to provide measures of fitness and dietary breadth between seasons (fall vs. summer) and between several locations within the estuary. Results suggest a low dietary breadth that overlaps with tadpole madtom (Noturus gyrinus); tubenose goby diet was mostly comprised of Crustacea, regardless of location or season. Growth modelling demonstrates that tubenose gobies reach a small maximum size and are short-lived, indicating an r-selected life history. The Gompertz function is preferred for modelling the growth of this species.