written by Lillian Denecke
This past fall and winter, Great Lakes Center technician Lillian Denecke evaluated deep-water videos collected from Lakes Ontario, Huron, Michigan, and Erie to estimate round goby (Neogobius melanostomus) abundance. This project was funded by the U.S. EPA Great Lakes National Program Office (GLNPO) as a part of the Cooperative Science and Monitoring Initiative (CSMI) to provide further insight on the impacts of the round goby on benthic communities. The round goby is a non-native benthic fish species first introduced to the Great Lakes in 1990 via the St. Clair River and has been known to prey on benthic macroinvertebrates,
including the invasive ecosystem engineers quagga and zebra mussels (Dreissena spp.). Use of underwater videography offers a solution to monitoring round goby density in deep lakes, since estimations of goby density via bottom trawls are difficult due to their habitat preference for rocky benthic areas, leading to underestimations.
To collect videos of lake benthos, a Benthic Imaging System (BIS) equipped with GoPros and underwater lights was lowered to the lake bottom from the U.S. EPA R/V Lake Guardian. Images were clipped from the videos, and gobies were identified and counted for density. Gobies were present at 35% of stations in Ontario, 11% in Erie, 9% in Huron, and 3% in Michigan. The use of videography was a success, with only minor challenges along the way. Sometimes it was difficult to clearly identify organisms because the location was shallow and murky. Other times it could be challenging to count numerous fish moving at once; for example, a location in Lake Ontario had an average of 34 individuals in each replicate, making it difficult to count individual fish but made for an interesting video. In addition to the round goby, other benthic organisms were visible in videos such as native opossum shrimp (Mysis diluviana) and the invasive quagga and zebra mussels throughout all four lakes. Occasionally, other species of fish such as various shiners and deepwater sculpin (Myoxocephalus thompsonii) were present.
Lillian presented the results from this work virtually at the GLNPO collaborators meeting in February and hopes to continue working on this project and present more results at the International Association for Great Lakes Research meeting in Windsor, Ontario, this May. The next steps for this project are to finish processing the Ponar samples from CSMI Ontario 2023 and to compare round goby density to Driessena spp. density and size class structures to investigate how round gobies may be impacting Dreissena spp.
Image caption: An image taken from a video clip from Lake Ontario with round gobies circled in yellow.
