Can anyone tell me what I have going on with my CNBG? I have some that have a black patch extending from the back of the head and along both sides of the dorsal fin. They seem healthy and are eating good. I had a few this summer but now it looks like it maybe about a 3rd are showing this. The one I described has about the largest area I have seen. Most have patches about 1/2 that size. I have seen similar patches on bass in the area lakes but its rare.
Thanks for any help you can provide.

Check out the link below. Maybe this?

https://mdc.mo.gov/fishing/fish-diseases/melanosis-black-spot-blotchy-bass

Pond Owner: "I think it is time to start culling some largemouth bass this year."

Bass in the pond: "No largemouth bass in here. Just us 'ol spotted bass."


In more seriousness, in jpsdad's link it appears to be a genetic condition. If it is only in your CNBG, and they are all related, then perhaps not a problem?

If it starts showing up on your OTHER fish species in the pond, then it likely does have a disease or pathogen vector in your pond.

Have you cleaned any of your CNBG? Does the meat adjacent to the surface patches appear normal?

Not uncommon at all coming out of winter as the days get longer. In March I see this all over Texoma in LMB. I see 1-2 in my SMB every year. It's (I believe) a behavioral trait.

Never seen it. Pretty neat

Snipe,

If you think it could be behavioral AND you see it coming out of winter, do you think that the fish are "sunning" themselves to get warmer in the shallowest water? (About 50% of total UV radiation can reach a foot deep in water.)

Do the black spots disappear later in the year? (For either Texoma LMB, or your own SMB.)

There is a fair amount of info out on this.. some say it's a disease, I disagree as I see it in many locations pre-spawn through post-spawn, then you may not see it again until the next spring.
In Hatchery setting, we see the males show this trait but not every year, some may be very small patches, sometimes larger around the head area.
Personally, I have nothing scientifically to offer on this, but our SW Hatchery manager says it is not a "sunburn" in his eyes, he believes it has more to do with environmental factors and said he thinks he sees it more with a warming trend which would align with my observations of pre to post-spawn.

From jpsdad's article:
"Melanosis is not an infection but an increase in the melanin in the skin."