Round goby swimming near zebra mussels (Credit: Joi Ito, via Flickr)
The populations of species at the bottom of Great Lakes food chains have been decreasing since 1998, according to a U.S. Geological Survey release.
Phytoplankton, invertebrates and small prey fish populations have all been shrinking, researchers found. They suspect increased competition from invasive species has lessened nutrient availability for native species.
The study was conducted with previously recorded data from a variety of sources. Analysis showed prey fish and zooplankton decreased in Lakes Michigan, Huron, Ontario and Superior from 1998 to 2010.
Central Lake Erie also saw a decrease in prey fish. The invasive round goby, however, has become a prominent prey fish in the lake’s western basin where prey fish have increased slightly.
Image: Round goby swimming near zebra mussels (Credit: Joi Ito, via Flickr)