Black Marks, Blotches or Spots on Bass...OH MY!

I, like many anglers in my region, have been catching both largemouth smallmouth bass that exhibit large irregular black blotches or spots for many years now.  When I first started noticing fish with these weird markings, they occurred mostly with largemouth.  In recent years, I've been seeing them in smallies too.  The bass that I've caught with the spots were large adults and appeared to be really fat and healthy.

Black blotches or spots, like the ones shown here on a fat healthy largemouth bass from the Upper Tidal Potomac River caught by my buddy Bob Barber, are nothing to worry about.

In addition to the local waters that I fish, anglers in other states and, from what I've read, in Canada, have been seeing this phenomenon as well.  Naturally, when weird stuff happens to fish, anglers and biologists alike tend to think that the causes surround parasitic activity, water quality issues, or mishandling of catch and release fish.  These concerns turn to complaints and assumptions, and eventually research into the potential problem, and rightly so.  That's how the process usually works.

So, what are the spots and are they anything to worry about?  The condition is termed hyperpigmented melanosis, which is a fancy term for pigment discoloration.  The condition seems to occur in larger adult fish more often than juveniles.  The spots don't appear to be permanent.  Often, the coloration often returns to normal after a period of time.  And, researchers have found the fish exhibiting the spots seem to be otherwise very healthy.  Of the ones that I've caught over the years, I tend to agree, they seem very healthy.

The black blotches occur just about anywhere on bass, even the lips as shown here from a largemouth caught in a small Maryland lake.  The patterns can be simple spots, or large irregular blotches.  I think that they give the bass character!

Anglers are increasingly reporting occurrences all over the country that, in some cases, are on waters that are already troubled by poor water quality or pollution.  The fears about their home waters may be well founded, but perhaps the link to the spots may not be.  Reports of people catching fish with the spots seem to be increasing, but it doesn't necessarily mean that the number of affected fish is increasing.  People are noticing, and with the amount of free exchange of info over the net, are simply talking more about it.

Here's the same bass shown in the previous picture, displaying several spots and blotches on the lips, body, gill and fins.

Researchers speculated for some time that stress of some form may be the cause.  Stress resulting from fish handling (perhaps catch and release), parasitic activity, disease, natural injuries to the skin, bacterial or viral infections, pollution or poor water quality have been suspected causes.  Even though all of those could possibly result in the condition, there's no evidence to directly support that this type of melanosis is caused by those factors, and researchers have stated that the symptoms could very well be genetic or hormonal.

In many fishing forums, more and more people are posting fishing reports with pictures of affected fish along with voicing their concerns.  With all of the buzz about blotchy bass, and after catching a few myself, I decided to do my own research.  I really couldn't find much on the web except that nobody really knows that causes the spots, that the fish appear healthy, and that researchers at Auburn University are studying the phenomenon.  I was not able to find anything about the results of the Auburn study.

Gene Mueller, who writes and awesome blog that I urge you all to visit, Gene Mueller's World of Fishing & Hunting, mentioned to me that these spots aren't anything to worry about as he had spoken to Maryland DNR officials, and they assured him that the spots were nothing to worry about.  In addition, the Maryland Fisheries website mentioned in their fishing report in reply to a post something to that effect.

I wholeheartedly agree with Gene and am not worried about the spots.  But I'm not sure that the rest of the angling community feels the same way.  So, I wondered that, with all the increased concern about blotches on bass, maybe I'd address the topic here to put forth some of the latest info.

Wil Wegman recently wrote a detailed piece in the April issue of B.A.S.S. Times on the topic.  He interviewed various people researching the spots, and shared what he learned with the B.A.S.S. Times followers.  he relates that former Professor John Grizzle of the Southeastern Cooperative Fish Disease Laboratory at Auburn University and Associate Professor Jeff Terhune, who currently runs the lab, concur on their take on the spots. 

Dr. Terhune states that "...there could be lot's of causes, some anecdotal and some potentially real.  Even spawning may create lesions or sores that heal in this manner.  Genetics can also play a big part.  Overall, most of the hyperpigmentation that I am aware of causes no harm to the fish, otherwise you would see fish in poor condition (i.e. thin) or with some other diseased condition."

Mr. Wegman also reported that Dr. Terhune believes that "though anglers are targeted as causing the strange bass coloration, it's far more likely to be a natural occurrence that has little to do with how much a bass has been handled."  That doesn't let anglers off the hook though, as it's our responsibility to carefully release our catch (if that's our intent) and handle the fish with the utmost care as much as possible. 

Then again, many people are questioning what, in some bodies of water, seems to be a more recent phenomenon.  The Susquehanna River in particular where more and more smallmouth bass seem to be exhibiting the spots than many Susky veterans can ever remember.  Recent water quality issues that are known to cause other problems with the health of the bass populations there, along with dramatic decreased young of the year counts, have resulted in recent regulations closing all bass fishing in large stretches of the popular river during the spawn, including catch and release fishing (beginning May 2012).  Perhaps there is something to this. 

Some veteran anglers are asking for more detailed studies by Pennsylvania officials to see if the spots are indeed linked in some way to the troubles of that river.  Perhaps they'll find out one way or another.  If they're related, they could be an indicator of bigger problems.  At the very least, even if the spots prove harmless, more attention would be given to address the real causes of the decline in bass numbers there.  More to come I'm sure.

This Susquehanna River smallmouth bass shows multiple black spots.  Anglers that frequent this popular river are extremely concerned about increased occurrences of the spots in their river, especially in light of other problems related to pollution there.  Photo Courtesy of Bill Yingling, M.D.

So, in summary, as Gene pointed out to me months ago, the black blotches appear to be nothing to worry about, at least on the individual bass studied.  But, could they be an indicator of bigger problems on some bodies of water?  Our focus should be on improving the water quality as much as possible, especially if the spots really are an indicator that is tied to water quality.  The bigger problems that have already identified are decreased young of the year smallies in our upper rivers along with discoveries of intersexed bass, and bacterial lesions more than likely due to poor water quality and various forms of pollutants.  But that's a blog topic for another day.

By the way, I've been a lifetime member of B.A.S.S. for many years.  Their publications, Bassmaster Magazine and B.A.S.S. Times are highly informative.  They are a must for the serious bass angler.  I've saved every copy since becoming a member many years ago.  Often, the information found in both publications is useful to other anglers as well, especially topics regarding fishing politics and conservation.  I highly recommend both publications.  I'd like to thank Bassmaster and B.A.S.S. Times for their contribution and permission to share their research, and Wil Wegman for writing such an informative article.