Leeches on fish not as rare as one might think
BY DALE BOWMAN firstname.lastname@example.org July 27, 2013 1:24AM
Leeches are more common than often thought, as this leech showed during a fish survey this spring near Green Bay. | Dale Bowman/For Sun-Times Media
Updated: August 29, 2013 7:52PM
Joey Rizzio spotted freshwater drum eating zebra mussels Tuesday on his way to work at Endorfins Charter at Montrose Harbor.
‘‘I put a jig down and was catching them one after another,’’ he said.
Later, while de-gilling one of them, he noticed ‘‘something weird’’ on a gill.
There’s always something changing in Lake Michigan and the Great Lakes. This is another one.
‘‘I stumped a lot of people on that one,’’ Rizzio said. ‘‘Some of those people have been on the lakefront 60 or 70 years.’’
Include him among the stumped.
‘‘I knew it was some kind of bloodsucker because it was attached to the gills,’’ Rizzio, 29, said. ‘‘When I pulled it off, it kind of made a popping noise, like it was stuck on there.’’
It was weird enough that he took it to Mike Repa, the venerable and crotchety counterman at Park Bait, who had no idea what it was.
Later that day, Ken ‘‘The Lakefront Lip’’ Schneider came in and was baffled. Later still, Schneider dug up the likely ID of a leech: Actinobdella pediculate.
‘‘That does look like a leech, but it is difficult to identify it to species,’’ Phil Willink, a senior research biologist at the John G. Shedd Aquarium, emailed after seeing a photo. ‘‘There are over 40 species in the Great Lakes, but not all parasitize fish.’’
‘‘It is difficult to determine exact species from these images since the leech is all curled up, but the suggested ID seems sound since that is what has been most reported on freshwater drum,’’ emailed Solomon David, a postdoctoral research associate at the Shedd who taught parasitology for eight years at the University of Michigan.
That particular leech has been reported in drum around the Great Lakes.
‘‘I do not profess to be a leech expert, but I will say that leeches on fish are more common than most people realize,’’ Willink emailed. ‘‘One just needs to look for them.
‘‘In regards to Actinobdella pediculate, this one seems to be becoming more common in the Great Lakes or is at least spreading to new areas of the Great Lakes. As far as I can tell, it is native to the region, just seems to be on the rise.’’
‘‘Leeches are seldom a major issue for their hosts as it’s not in any parasite’s best interest to kill the host (evolutionarily speaking and on a personal level for the individual parasite),’’ Solomon emailed.
‘‘I think you were with us when we found some pretty big leeches in the ditch sites of the Duck Creek project [near Green Bay] . . . so they are on toads, other amphibians and fishes out there, too. . . . Generally haven’t seen direct adverse effects of leeches like this (mild risk of secondary infection when the leech detaches as blood will freely flow for a bit due to anticoagulant in the leech bite, but that’s about it).’’
Why drum is most affected is not known.
Rizzio saved the leech, and the Illinois Department of Natural Resources will get it this week. And I think he had good reason, considering all the changes — good and bad — in the Great Lakes.
‘‘I don’t just throw stuff back when I see stuff like that,’’ Rizzio said.