The Stream Doctor

June 28th, 2004

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

Q. Being a fish biologist and familiar with some of your work, I was quite pleased to get a chance to "talk" with you. I live in central WA state and have recently (3 years) started fly fishing. One disparity has always puzzled me to some degree. Why are the rivers of Montana and some of the other Rocky Mt. states so much better at producing more and larger fish than the rivers in my neck of the woods?

A. You're exactly right, there are many factors that interact to produce the productive characteristics of streams. You cite some of the major out-of-stream factors, and it would take me more space than we have here to enumerate the many in-stream factors that influence productivity. I'm not trying to dodge your question; it is just too complex to tackle here. Suffice it to say that one of the crucial points influencing salmonid production (and I'm speaking now about resident trout, not anadromous salmonids) is the amount and type of secondary production in the form of trout food (usually insects). Now, substratum, nutrients, and light regime are important factors influencing the amount of primary production (algal growth) in a stream which is a major source of food and energy for the insects, so we can add these to your list. Terrestrial organic matter falling into the water and decomposing is another important food source for invertebrates. From the other end, predation, cover, suitable spawning habitat, and fishing pressure can all influence the numbers of fish present. I'm just getting rolling here, but better stop before I have to let a lot of loose ends hanging. I wrote an article entitled "Sunshine, bugs and trout" in the Spring 1995 issue of TROUT that attempts to briefly describe how stream ecosystems function and what factors influence the structure and function of flowing waters. Though not exhaustively detailed, it does a pretty fair job of hitting the highlights. If you'd like to read it and can't locate a copy, let me know and I can send you a xerox copy of the article. Contact me at

I'm going to throw out a couple of other observations pertaining to your question. I went to WA in 1961 after having been raised in CO (where I now live) and working as a fish biologist in CO and MT. I was amazed at the emphasis WA fish biologists gave to anadromous salmonids and at how little they seemed to be interested in resident trout populations. My neighbor and co-worker was a fishery biologist and he gently made me aware of where the priorities were in the state. It seemed to me that resident trout were just above trash fish in priority! This led me to believe that the paucity of trout fly fishing in the state was possibly related to management decisions, i.e., manage the streams for salmon and steelhead and don't worry about resident trout. I also came to wonder if healthy resident trout populations could exist in streams that supported extensive anadromous fisheries; could resident trout populations compete with larger salmonids?. However, all you have to do is look at the Deschutes River in Oregon to see that the two can co-exist.

Well, I've talked all around your basic question of why the fishing is better in the Rockies than in the Cascades. I agree, and rather that fight it when I retired, I moved back to CO!!

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

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

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