sturgeon trade-offs with the caspian sea

Another threat to sturgeon is the invasion of the Caspian by a fist-sized comb jellyfish (Mnemiopsis leidyi) native to North America. Scientists suspect the alien jellyfish first arrived in the Black Sea—which is connected to the Caspian by the Don and Volga rivers—in 1982, carried in the ballast water of ships from the Chesapeake Bay. According to reports by Henri Dumont, a biologist at Ghent University in Belgium, the voracious jellyfish devoured nearly all of the Black Sea’s zooplankton, causing a massive crash of the native fish population and crippling the local fishing industry there. This comb jellyfish species, a self-fertilizing hermaphrodite, was found in the Caspian in 1999. By the summer of 2000, the entire sea was teeming with them.

From Caspain Calamaties by John Tidwell. Zoogoer May | June 2001

Take that Caspians! Thanks for the zebra mussel!

Ironic note...

Zebra mussels have had positive impacts on parts of the Great Lakes ecosystems. Many native fish, birds, and other animals eat young and adult zebra mussels. Migratory ducks have changed their flight patterns in response to zebra mussel colonies. Lake sturgeon feed heavily on zebra mussels, as do yellow perch, freshwater drum, catfish, and all the sunfish. The increase in aquatic plants provides excellent nursery areas for young fish and other animals, leading to increases in smallmouth bass populations in Lake St. Clair and the Huron River.

From the USGS Great Lakes Science Center