The Stream Doctor

June 20th, 2005

Email YOUR Questions directly to the Stream Doctor. This is your opportunity to get an experts professional opinion on anything stream related.


Q. Sorry, not an inside tip on where to find the big one.

Ladyfisher suggested that I contact you with my question on brown trout spots. Attached are a couple of photos that I hope don't gum up the works too much with download time.

I'm curious to know why some browns are more spotty than others. Nature, nurture, age, a combination of all? Which factors are more important? The fish with the most spots came from healthier water, by the way.

Thanks for your time.

A. I'm probably not going to give you satisfactory answers to your questions, but rather give you some quotes from some expert's writing in a couple of books.

Dr. Bob Behnke in his book Trout and Salmon of North America says, "...but color varies among individuals from pale, silvery gray tinted with shades of greenish blue, to deep golden yellow, dark red, or orange that suffuses the lower half of the body. Because of the mixed and diverse ancestry of brown trout introduced into North America, nearly the complete spectrum of spotting and coloration in brown trout world wide can be found among American brown trout populations." This quotation would seem to infer that genetics plays a significant role in the development of spots.

Robert A. Bachman, author of the chapter on brown trout in the book Trout, has this to say about the subject: "The almost limitless variations of color, shape, spot patterns, fin markings…have been the source of frustration, confusion, acrimonious debate and resignation for more than a hundred years." He then goes on to describe the basic coloration and variations of brown trout and then says, "Although all forms and races of brown trout exhibit some or all of the above characteristics in the juvenile, or parr stages, much of the coloration disappears or is masked by a silvery coloration when the trout lives in deep, clear lakes of when it smoltifies.... Further, the black and red spots on some forms are more irregularly shaped than on other forms, and when the coloration is masked by a proliferation of guanophores..., markings and coloration are poor, if not useless, means of identification." The author goes on to discuss the use of spot characteristics for use in identification and also discusses the fact that the brown trout is the only trout that has red or orange spots on the margin of the adipose fin; this, however, is often lacking in hatchery-reared browns unless they have been fed a special diet or they survive long enough in the wild to eat enough natural food to develop this distinctive color characteristic. I suspect that most of us have noticed that lake browns are lighter in color than stream-bred browns; this would lend credence the "nature" aspect of your question, and the food aspect would support "nurture."

So there you have it - nature and nurture both look like they can play a part, and you can't leave out genetics.

Hope this sheds some light on the subject. ~ Bert

If you have a question, please feel free to contact me.
~ C. E. (Bert) Cushing, aka Streamdoctor
105 W. Cherokee Dr.
Estes Park, CO 80517
Phone: 970-577-1584
Email: streamdoctor@aol.com

The 'Stream Doctor' is a retired professional stream ecologist and author, now living in the West and spending way too much time fly-fishing. You are invited to submit questions relating to anything stream related directly to him for use in this Q & A Feature at streamdoctor@aol.com.


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