Diet and bathymetric distribution of juvenile Lake Trout Salvelinus namaycush in Lake Huron

Abstract

Rehabilitation efforts for Lake Trout Salvelinus namaycush in Lake Huron have resulted in increased capture of young wild Lake Trout in annual bottom trawl surveys conducted by the U.S. Geological Survey. To better understand the ecology of juvenile (<400 mm) Lake Trout, we summarized the spatial distribution of their capture in bottom trawls at six ports in Lake Huron during October/November 2008–2017 and analyzed diets of wild (n = 306 of 337 total) and hatchery-origin (n = 18 of 30 total) fish captured. Lake Trout ranged in size from 27 to 399 mm, representing at least three age-classes, and 92% were wild origin. Most wild juvenile Lake Trout (83%) were captured at 46–64 m depths at the two northernmost ports, typically below the thermocline. Mysis diluviana was the most prevalent prey type, found in 75% of wild fish with non-empty stomachs, followed by two non-native species: Spiny Water Flea Bythotrephes longimanus (31%) and Round Goby Neogobius melanostomus (12%). Small Lake Trout (<185 mm) consumed invertebrates but transitioned to mostly fish-based diets by >185 mm (∼age 2). The variety of taxa consumed by young Lake Trout increased with length. Further declines in Mysis populations due to increased predation pressure after the loss of Diporeia from the system may hinder the recovery of wild Lake Trout, and although they have been able to utilize invasive species as prey, impacts to Lake Trout growth remain unknown. Additional research on the habitat use and diets of wild juvenile Lake Trout may provide insight into the reasons behind the recent successful natural reproduction and recruitment of Lake Trout in Lake Huron.

Keywords:

• rearing habitat
• restoration
• Mysis

Acknowledgments

We thank the crews of the USGS R/V Grayling and R/V Arcticus for assistance in sampling and numerous field and laboratory technicians for help collecting and processing the samples. Use of trade names is for descriptive purposes and does not imply endorsement by USGS. All sampling and handling of fish during research were carried out in accordance with guidelines for the care and use of fishes by the American Fisheries Society (http://fisheries.org/docs/wp/Guidelines-for-Use-of-Fishes.pdf). All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. Data are available for download from ScienceBase: https://doi.org/10.5066/P9Y67TGN

Author contributions

E. Roseman was responsible for study conception and design. E. Roseman and S. Riley supervised and participated in fieldwork, and S. Farha, T. Tucker, and D. Bowser participated in fieldwork. E. Roseman, S. Riley, and T. Tucker wrote the manuscript, T. Tucker performed statistical analyses and created figures and tables, S. Farha assisted with data preparation, and S. Jackson and D. Bowser performed stomach content analyses.

Supplementary material

Supplementary material for this article can be viewed on-line at www.taylorandfrancis.com

Additional information

Funding

This project was partially supported by the Great Lakes Restoration Initiative.