Cowlitzfisherman -
Not sure that I completely understand your questions or that I can expalin my statements any clearer however here goes.

Our fish under constant selective pressures from their environments - those that are best suited for a particular condition are those most likely to survive to spawn and pass on those traits to future generations. As we make our rivers more alike - through confining the channels, diverting and/or regulatiing flows, etc - the fish become more similar. Thus the lost of diversity.

Lets take one simple trait - spawning timing. It is clear the timing of the spawning of our wild steelhead is determined in large part by the hydrograph of their watershed. Those systems whose hydrographs are dominated by rainfall (high lows in the late fall/early winter and declining flows from spring into the summer) have typical peak steelhead spawning of late March/early April (examples would coastal streams). Those systems dominated by snow run off (high flows in both the fall/early winter and late spring/earlysummer with declining flows occurring in mid summer) have peak spawning from late April (example Snohomish) or mid-May (example Skagit system). The reason of course is that spawning is timed so that the fry will emerge from the gravel so that gains from have longer rearing (early emergence) and high mortality due to excessive flows (need later emergence) are balanced to produce the most successful survival strategy. Thus the spawning is timed so that the fry pop from the gravel as soon as the spring/summer flows begin coming down. When man steps in a places a dam on a system to capture the summer run-off for power or water needs the downstream hydrograph is changed thus the fry survival matrix changes meaning the spawning timing changes. As more and more rivers are "managed" for our water needs their hydrographs become similar; ergo their fish become similar.

Your dinosaur example is interesting- they were successful for 10s of millions of years. However the prevailing theory is that a large asteroid crashing into the earth drastically and suddenly changed their habitats through dramatic climatic changes. They were not able to adapt and became extinct. My concern is that our alterations of our streams is becoming the steelhead's asteroid.

Fun5acres -
I understand your desire for property right protection. It is certainly your right to advocate that position. However at the same time it is disingenuous not to acnowledge that allowing everyone to do what they please with "their land" has dire consequences to most natural resources.

The question becomes -How much are we willing to limit individual property rights to protect public resources. Nearly everyone would agree it is not in societies best interest for me to locate a nuclear waste site in my back yard ever though I may benefit greatly financially. We seem to differ on how much infringement of private rights is acceptable to protect fish, wildlife, water or quality of life resoources. Do we wish to keep those resources? If so how much? Are we willing to pay for it either in reduced rights or financial reimbursements? Those questions keep boards like this lively!

Tight lines
Smalma