Bass with Black Splotches

[Smiths.R]

I searched for this, but didn't find anything.  I also refuse to believe no one asked about this yet...

Last night I was fishing and saw a bass just cruising.  It had big black splotches all over it.  Just curious what that might be.  Some kind of mold?  I would assume it can't be good whatever it is.

[Paul Roberts]

It's a known thing, but the cause is not. Search bigindianabass.com for some discussion.

[Wayne P.]

It's quite common on the Tidal Potomac River.

[Sfritr]

I have heard different explanations as to why this happens. 

1.  I have been told that this is caused by handling the fish and removing their slime coating.  It is like a sunburn to a fish.

2.  I have also heard that this is very common with fish that are in a very healthy environment and is like birthmark on healthy fish

I can't say which may be true or false.  However, I have never caught a fish that had these markings that looked ill or unhealthy. 

[Paul Roberts]

Bruises do turn black and this is common and lasts a week or so. But the black blotch phenomenon is something else. I believe it's seasonal too. Do check bigindianabass.com -Brian's been following it,

[IDbasser]

Here is one that my dad caught last year here in Idaho.

[SkeetyCCTX]

I first saw the big black splotches on fish when I went to Conroe last summer!  The fish looked healthy but it freaked me out!  I thought maybe it was a pollution thing from run-off or something!  However, my cousin told me they were caused because of their diet!  He said it means that the fish are eating lots of crawfish! 

I dont know if the crawfish thing is true, because I have never seen this at my local lake (mathis) which is a primarily crawfish lake, but I do think it is a diet based thing which is harmless, becuase I am starting to see it in other places and all the fish look very healthy!

Recently, I have seen fish at both Choke Canyon and Falcon with these spots, though not as many of them as that day at Conroe!  These spots are usually the size of a quarter and very black and distinct.  Its like they have been touched with a magic marker!  I do feel it is something in their diet and a sign of lots of protein, considering the state of the lakes in which I am seeing it!

I am interested in what it really is though!

[IDbasser]

the 2 main places I fish the bass feed mainly on crawdads, I have only noticed the one I posted with the black patches, I may have caugt some with smaller ones, but I had to get a pic of the one with a black head.

[grimlin]

Birthmark...

[Team9nine]

Like Paul mentioned, while the occurence is well documented, nobody knows for certain what the cause is. It is most likely not diet related though. Some speculate that it might be related to C&R and excess handling, others think genetic, while still some believe it is environmental (infection or chemical). I've spoken to the lead fish pathologist here in my state and he speculated either chemical or parasitic reaction, but he couldn't state either with any certainty. The researchers at Auburn U. were supposed to be undertaking a study to determine cause, but I have never received a response from them to see if that study ever occurred. I certainly haven't seen anything in the literature documenting any such research. I've watched for it quite a bit here and it seems to be more of a seasonal thing on many of my local waters with the highest incidences in the spring, but that is purely anecdotal. I really need to track it more. I do have pictures of bass I've caught going back nearly 20 years that displayed the blotches, so it is not a "new" thing, at least not in my waters.

-T9

[OH-bass614]

one of the resivoirs i fish has alot of these fish and all on the big ones have it and i mean all so i think its good. but the slime coat removal thing could be true too because its a very pressured and poluted river

[Long Mike]

Whazamatter? Haven't you guys heard of Leopard bass?   

[fmoore]

I asked this question last October on a different site and this is the answer I got:

I just read an article on this. The spots are caused by a trematode worm. It gets into the fish by birds who eat fish. The worms lay eggs in the digestive tracts of birds. Who then defecate where snails eat the larvae. Then in 6 weeks tiny cercariae emerge. The cercariae swim around until they find fish to burrow into. The black spot forms as the fish' body reacts by covering the cyst tissue. The life cycle is completed when a bird eats an infected fish the cysts rupture, and the parasite is freed to mature in the bird's gut and produce more eggs. Though some consider the spots unappetizing, black spots cannot affect humans. This came out of in-fisherman janurary 2009 page 12.

[Paul Roberts]

Trematodes are something different. They create tiny black spots, each very round and consistent in size and shape, sometimes lots of them, on fish.

The "black spot/patches" thing is something else -the spots are large and appear to look like pigment

[chia-chaser]

This is called Melanosis, its a pigment dissorder(Melanin). According to the experts, it has no effect on the health of the fish, just wild looking. The large mouth here in east Tn commonly have this, seems like more in the summer, then in the cooler Months.

[.dsaavedra.]

I asked this question last October on a different site and this is the answer I got:

I just read an article on this. The spots are caused by a trematode worm. It gets into the fish by birds who eat fish. The worms lay eggs in the digestive tracts of birds. Who then defecate where snails eat the larvae. Then in 6 weeks tiny cercariae emerge. The cercariae swim around until they find fish to burrow into. The black spot forms as the fish' body reacts by covering the cyst tissue. The life cycle is completed when a bird eats an infected fish the cysts rupture, and the parasite is freed to mature in the bird's gut and produce more eggs. Though some consider the spots unappetizing, black spots cannot affect humans. This came out of in-fisherman janurary 2009 page 12.

yeah this is something different, "black spot disease". most of the golden shiners in my creek have it. the black spots are very numerous, and all the size of a pin head.

this is a golden shiner i got from the creek and had in my aquarium. terrible pic but you can see the spots on it.

the condition in question is melanosis. the last 5lb10oz fish i caught had it. its all over fish in the potomac. not sure why though.

[Dwight Hottle]

In lake erie we catch smallie with black splotches usually in the spring. I read somewhere that it has to do with wintering in close proximity to each other. That would suggest a fungus or viral condition. Here is an example from yesterday.   

[owl]

I went to my local lake to test my tm. Big largemouth  were hitting a black craw like crazy .  One had several large black splotches. I cant remember ever seeing one. Looked like freckles