Diet and foraging of Round Goby (Neogobius melanostomus) in a contaminated harbour

Abstract

Anthropogenic pollution and the introduction of invasive species are two contributing factors to ecosystem degradation. Although Hamilton Harbour (Ontario, Canada), a highly impacted ecosystem, is well-studied, the diet, trophic position, and foraging behaviour of the invasive Round Goby (Neogobius melanostomus) in this area is not well understood. In this study, we compared digestive tract contents, foraging behaviour, and stable isotope values of Round Goby from sites of low and high sediment contamination in Hamilton Harbour. We also assessed prey availability by conducting sediment invertebrate abundance analyses at these sites. Regardless of site, Chironomids, Cladocerans, Copepods and Dreissenids were the most common food items found in Round Goby digestive tracts, and females always had heavier gut contents compared to males. Fish from the high contamination site consumed fewer prey items, had lower gut fullness scores, and fed at a lower trophic level based on lower δ¹³C and δ¹⁵N values. Our results suggest that Round Goby living in highly contaminated areas are feeding less than Round Goby from areas of lower contamination, but that these diet differences do not reflect differences in prey availability. Fish from the high contamination site also typically moved more slowly while foraging. Taken together, these results provide an analysis of the main prey items of Round Goby in Hamilton Harbour, and demonstrate how polluted environments can impact diet, trophic position, and foraging of an introduced fish species.

Keywords:

• stable isotopes
• invasive species
• trophic position
• remediation
• Area of Concern
• Hamilton Harbour

Acknowledgements

We would like to thank M. Baxter and the Hamilton Port Authority for permissions, A. Hussey for help with stable isotope analyses, R. Dermott for advice on sediment analysis protocols, B. Bolker and J. Dushoff for assistance with statistical analyses, A. Bose for helpful comments on the manuscript, and many previous students that have helped with field work for this project: N. Sopinka, J. Young, P. Capelle, R. Caldwell, O. Petric, G. Fortin, N. Berlin, and C. Lau.

Funding

This project was supported by NSERC PGS scholarships (to E. McCallum and J. Marentette), NSERC Discovery Grants and Canada Research Chair Programs (to S. Balshine and A. Fisk), and funding from Fisheries and Oceans, Canada (to S. Balshine).

Supplemental material

Supplemental data for this article can be accessed on the publisher's website.