If there are 182 documented invasive species present in the Great Lakes, one can only wonder why just a few of them can't be welcomed as a benefit to that tortured ecosystem.

With passage of any meaningful ballast water laws for transoceanic ships entering the Great Lakes constantly stonewalled at the federal level, it's just a matter of time before more invasive species arrive via contaminated bilge water. I continue to hold hope the next species might be a little more user-friendly, but my hopes were dashed again with the announcement of #183 showing up in Muskegon.

A species of shrimp called a "mysid" by shrimp biologists is here and presumed to be making itself at home in the Great Lakes. Previously found only in the seas of eastern Europe, the new arrival was discovered in the channel between Muskegon Lake and Lake Michigan.

It's proper name is "hemimysis anomala", but I'm just going to call it a "hemi."

Steve Pothoven, an NOAA fisheries biologist who found healthy swarms of the bloody-red hemis last November, said they came from the Ponto-Caspian region -- the same area that gave us zebra mussels, quagga mussels and the goby. Pothoven surmised the half-inch-long shrimp were likely brought into the Great Lakes in the ballast water of an oceangoing freighter.

He's probably right, but the statement causes immediate concern. Ocean freighters are rare visitors to Muskegon. The initial invasion probably happened somewhere else in the lakes and the population has spread to Muskegon.

Both juveniles and mature females were identified from the Muskegon channel population, indicating the species is likely reproducing in the Great Lakes elsewhere. Where they got started, how long ago they arrived and how widespread the new immigrants have become is unknown.

So what changes can be expected to occur in the Great Lakes because of this new invader? There's no way to determine that just yet.

Perhaps the Great Lakes are doomed to become the North American version of the Caspian Sea. The dominant mollusk in most parts of the Great Lakes is now the zebra and quagga mussel, and the dominant zooplankton is the fishhook water flea. Lake-bottom habitats are becoming more and more dominated by the round goby and ruffe -- all species originating from that region of northern Europe.

If there's a silver lining to this news, it's that hemis actually prey upon fishhook and spiny water fleas, two other invasive zooplankton species which up to now have added little to the lakes' puzzling food chain. Hemis themselves are high in fat and apparently eagerly gobbled up by young fish. Overseas, they have actually been planted in lakes to boost fish production.

So here comes the hemi. Only time will tell what that means.

In the meantime, anyone want to wager what species will become #184? It's scheduled to arrive sometime in July if the normal timetable for invasive species is maintained.