Pond Boss Forums INTRO Questions & Observations Leeches in Largemouth bass mouths

Recently we've been catching largemouth bass that have anywhere from 1 to 5 leeches in their mouths. Upon further research, it appears that these leeches are Myzobdella lugubris. Does anyone have anymore information on these parasites? What effect will they have on our bass?

The research we've done shows that they lay their eggs on blue crabs. We shouldn't have blue crabs in our pond. Has anyone known these leeches to complete their life cylce on such things as crawfish instead of blue crabs?

Welcome to the PB forum.

Will this help?

Control of an Infestation of a Fish Leech
(Myzobdella lugubris) on Catfishes in
Tanks and Earthen Ponds
JOHN R. MORRISON AND STEVEN R. Fox1
U.S. Fish and Wildlife Service, Southeastern Fish Cultural Laboratory
Route 3, Box 86. Marion, Alabama 36756, USA
WILMER A. ROGERS
Department of Fisheries and Allied Aquacultures, Auburn University
Auburn University, Alabama 36849, USA
Abstract.—An infestation of a fish leech, Myzobdella lugubris, was discovered in a brood pond
containing female channel catfish Ictalurus punctatus and mixed-sex blue catfish 1. fur cat us. Three
chemical treatments—trichlorfon (0.5 mg/L), formalin (150 mg/L), and sodium chloride (1%)—
were compared for their effectiveness in the control of this parasite on individual fish held in tanks
at 21-23°C. Trichlorfon demonstrated the greatest leech reduction (34.4%), followed in effectiveness
by formalin (28.9%) and salt (17.2%). In further experiments at 26-28°C, 0.5 mg trichlorfon/L
achieved 91 % reduction of attached leeches in 6-h tank treatments and 100% reduction after 48
h in small ponds. Two applications of 0.5 mg trichlorfon/L 21 d apart were required for complete
leech elimination in the brood-fish pond. The initial application resulted in 100% reduction of
attached leeches on fish sampled 8 d afterward. Reinfestation occurred between 8 and 21 d after
treatment, as indicated by the presence of small leeches (5-12 mm in length). After the second
application, no leeches were observed on any of five subsequent sample dates over the remainder
of the 11-week study period. Trichlorfon seems to be effective in the control of M. lugubris on
brood channel and blue catfish when this chemical is used as an indefinite treatment at water
temperatures above 26°C. Repeat applications will probably be required in ponds with reproducing
leeches.

We get a leech that attaches inside the mouth of walleyes in the summer. A fish can have up to a dozen leeches in their mouth. I have no idea what species these leeches are.

Any ideas about whether they are harmful or not? Is it worth trying to do something about them?

Here is another study:

http://www2.selu.edu/Academics/ArtsSciences/oscar/journal6/lash/lash.htm

There was another study that showed them in a lake near Fort Smith Ark. wrt LMB and lepomis .

Here is a picture of an LMB from our pond with a small leech attached to the roof of it's mouth. I would interested to know if these leeches have a significant effect on WR's or growth rates.

I get them alot on the fish in my lake, too.
Hopefully someone can chime in as to their effects on their host.

A good contact you guys should make is with Chris Horton. Chris is the conservation manager with BASS. Chris will answer your questions.

Christopher.M.Horton@bassmaster.com

Another good source is Gene Gilliland. Gene has done alot of research on LM and works for Oklahoma Fish and Game. He and Hal Stram are the authors of "Keeping Bass Alive".

ggillokla@aol.com

Wildfowl/Steve B. -- I'll take a stab at this question. These small leeches/flukes are parasites. One rule of a "successful" parasite is to not kill your host. See my point?

I am not an expert on this topic. However, these small leeches are pretty darn common on many, many fishes in many locations. When I see a picture such as Steve's where just that single parasite is attached, then I really think the effect on fish growth and Wr is negligible.

I visited with another of our faculty members, asking if these leeches/flukes ever get sufficiently abundant in intensive fish culture operations that they might require treatment. He said he had never encountered them at problem levels.

So, when these parasites are present, but not overly abundant, I'd recommend that pondmeisters not worry. They are just part of the Mother Nature.

Thanks Dave! I will say that during the summer months I might find as many as 5 leeches in a LMB's mouth, 2 or 3 is more the norm, but the vast majority of the year the leeches are not present on the fish I catch. There is about a 6-8 week period where the leeches are very prevelant on the fish in our pond every summer. Once they start to disappear the sores in their mouths heal rather quickly. The picture I posted is one I took in Febuary and it is one I the very few times I have seen leeches attached during the cold water months.

Thanks Dave .

Guys you realize that you just got info from 2 PhD Fisheries Scientists on the subject via Dave going above and beyond the call of duty.

Yeh, now if we just knew more.......

Hey guys,

We really appreciate the replies and information! The concensus we had before the post was that the leeches were more of an eyesore to the fisherman than anything. I'm glad to see that same opinion being voiced here as well. Next time I go fishing, I'll try to remember the digital camera and post a few pics for those interested. Very good point about a parasite not wanting to kill its host! Kinda like a dog biting the hand that feeds it!

By the way, our pond is located in Southeast Texas along the gulf coast. It's approx. 65 acres and was constructed with scrapers. We dug most of the ditches this way, which then provided dirt for our levees.

Thanks again!