Margot Bergstrom under Dr. Allen Mensinger, Biology
Round gobies (Neogobius melanostomus) first invaded the Great Lakes in 1990 and were found in the Duluth/Superior harbor in 1995. The fish traveled from their native range of the Black and Caspian Seas in the ballast water of large shipping vessels. The round gobies can be recognized by their mottled coloring, fused pelvic fin, and small size. Round gobies live on the bottom and feed on aquatic invertebrates and mollusks when adults.
Round gobies have been found to negatively impact its closest morphological and ecological North American counterpart—the mottled sculpin (Cottus bairdii). Research in the Mensinger lab involves investigating other benthic species which could be affected by the round goby invasion in the St. Louis Harbor. These species include the Logperch (Percina caprodes), slimy sculpin (Cottus cognatus), and spoonhead sculpin (Cottus ricei). All of these species have diet overlap and the round gobies and sculpins may compete for breeding areas in the summer months.
Two different experiments are carried out to estimate the impact of the round gobies: predator-prey interactions and three week behavioral trials. The predator-prey interactions involve video taping a single fish feeding on small prey at different light levels. The prey (amphipods) is found in their natural habitat and the light levels simulate night, dawn/dusk, and daytime. The video tape is analyzed to measure the distance between the fish and amphipod right before the fish orientates towards the prey and tries to capture it. The angle between the fish and prey at this time is also measured. The goal of this experiment is to determine if the different species of fish are more successful at detecting prey at different times of the day.
The VDIL lab purchased Lolitrack video tracking software to aid in the analysis of the digital video from the predator-prey interactions. The video can be imported into this software and track the movement of the predator or prey. Both organisms need to have a mark on their bodies for the most effective tracking. The result of the tracking is an output of x and y coordinates at a selected sampling rate. This software is very effective at tracking fish movement for behavioral analysis.
The three week behavioral experiment involves placing one round goby with one or two native fish of the same species. Twenty-four trials can be run simultaneously in separate compartments in a mock stream set-up. All fish are weighed and measured every seven days. Data collected does suggest that round gobies are negatively impacting logperch. Ideally, more combinations of round gobies and natives could be tested to investigate how density influences the health of these fish.
This research can be applied in several areas. Knowing that round gobies have a more advanced sensory system could be used to improve management practices. The behavioral study results could help assess risk of inland lakes and streams and protect other native benthic fish.
Watch a sample movie of a round goby - click here