Black Spot Disease

[Roofin' Trouter]

I caught two brook trout this week that had Black Spot Disease. I had never run across that before in trout. I found some interesting stuff on the trematode fluke parasite. But , I seem to be getting conflicting information about how bad it is for the trout. I also thought it strange that it was on the brookies and no browns even though I regularly catch BT to ST 11:1 on that crick. Are BT more immune to the parasite? How common is this in PA?

 

[Dave_W]

Interesting. I've not seen this in trout.

It is, however, very common in creek chubs and red-breast sunfish in my experience.

 

[Roofin' Trouter]

I've seen it in chubs too but really didn't know what it was. The water was slightly stained and the fish was in the net before I got a look. I noticed it first when I reached in the net and felt spots on the skin. My first thought was that it felt like a chub.

 

[Mike]

Also never saw it on the nearly 100,000 wild trout that I handled in my career. It is, as was partially said, usually on creek chubs and blacknose dace. I have never seen it on a sunfish either. When found on stream fish at high infestation levels it is reported to thrive under low water/ temperature stress conditions and most streams that I can remember where I high infestations were low gradient, sluggish, and seemed to annually suffer from low flow. BND prefer transitional to cold temps while chubs prefer cool/warm transitional temps.

 

[Roofin' Trouter]

Thanks for the response,Mike. So you're telling me I caught the 2 in a million? I should've got Powerball tickets. This crick has good chub in some places where the beaver build and an excellent black nose dace population throughout most of it. Also, the beaver have brought more ducks over the past few years. I see mergansers,red heads, loons, as well as others quite regularly.
I did take a pic of one of the brookies and will post it when I have time to look at and load pics over the past year from SD card. I caught one on the same crick in January that seemed to have a slight growth deformity and am wondering if that could have been from Black Spot Disease.

 

[Mike]

From Vermont F&G: clearly occurs in more than just creek chubs and BND, but your description of the creek and its wildlife fits. Additionally, there must be snails present as well, which are a key component of the black spot trematode life cycle. Snail are often present in streams, but generally go unnoticed unless they are large or exceptionally numerous.

The occurrence in warmwater fish described by Dave, the below link’s associated photo, plus your find in ST have served my continuing education well. Thanks.

I’m also now reminded that I once found them in the muscle of harvested BG from a Schuylkill Co pond. There were no external signs of their presence.

https://vtfishandwildlife.com/sites/fishandwildlife/files/documents/Fish/FishHealth/Black_Spot.pdf

 

[Roofin' Trouter]

From Vermont F&G: clearly occurs in more than just creek chubs and BND, but your description of the creek and its wildlife fits. Additionally, there must be snails present as well, which are a key component of the black spot trematode life cycle. Snail are often present in streams, but generally go unnoticed unless they are large or exceptionally numerous.

The occurrence in warmwater fish described by Dave, the below link’s associated photo, plus your find in ST have served my continuing education well. Thanks.

I’m also now reminded that I once found them in the muscle of harvested BG from a Schuylkill Co pond. There were no external signs of their presence.

https://vtfishandwildlife.com/sites/fishandwildlife/files/documents/Fish/FishHealth/Black_Spot.pdf

Yes,there are some snails. I couldn't tell you what kind of snails but there are a few. I 've yet to find a good link to identify freshwater snails of PA. I found a DCNR link on snails put it has no illustrations.

 

[wcosner2]

Here is an example of a brookie we found during sampling in PA that I thought had the disease. In this particular section of the stream, a good proportion of the fish had the same black spots.

 

[Troutmeister]

Where do you see black spots?

 

[Roofin' Trouter]

They're most noticeable above anal fin in the pic posted. I have a pic that the black spots are more noticeable. A SD card reader is scheduled to arrive this week . When it does Ill post my pic.

 

[Roofin' Trouter]

Here is an example of a brookie we found during sampling in PA that I thought had the disease. In this particular section of the stream, a good proportion of the fish had the same black spots.
View attachment 1641232082

Thanks for the response. Were the black spots only on the brookies or did you see them in BT,too?

 

[wcosner2]

Thanks for the response. Were the black spots only on the brookies or did you see them in BT,too?

I believe we only saw them on the brook trout but there were a lot more ST than BT and we also caught one brook trout that was physically falling apart if I remember correctly.