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Rainbow Trout/Steelhead Biology Trout & Salmon

Steelhead And Trees II

by Matt Straw   |  November 13th, 2012 1

This steelhead, caught several days ago, apparently ran afoul of a commercial net or a large lure with trebles, the careless removal of which disfigured it for life. Or, since it’s obviously long since healed over, perhaps it’s a birth defect, or the result of a run-in with a bird or other predator when it was but a wee parr.

Undaunted, the spirit of the animal was unaffected. It persevered and obviously thrived. Had it not been able to find enough food early in life, it wouldn’t have such a healthy pr0file today. Many fortuitous turns, over the past four years, allowed this steelhead to escape the fates suffered by about 95% of its brothers and sisters born in the same riffle at the same time. And, from the very first moments in the life of this fish, it benefitted from trees.

Walking along rivers in forests, like this one, I sometimes wonder how many anglers are aware of the direct relationship between trees and fish. In many cases involving trout, salmon, and steelhead, trees are the difference between a thriving fishery and no fishery at all. With no trees on the bank, gripping the soil with roots, the spawning site where this fish was born would have silted in long ago. The river would widen and grow shallower, and the sheltering pools would fill in with sediment. Perhaps most importantly of all: With no trees on the bank to shade the water, the river would get warmer. Many degrees warmer. Too warm for cold-water fish like onchorynchus mykiss. Natural reproduction would become a thing of the past.

And that’s just the beginning. I read a published study once revealing that a fully-grown hardwood tree with branches hanging over a river or lake can provide hundreds of pounds of food per year in the form of fallen ants, spiders, inch worms, tent worms, flies, rodents, baby birds, etc. What percentage of the food that guaranteed survival for the fish in the photo above was provided by overhanging trees? No one can say for certain, but as it progressed from stage-to-stage, from hatchling to parr to smolt, it seems safe to say that some significant portion of its forage originated in the terrestrial world.

With nowhere to hide from larger brown trout, kingfishers, raccoons, and predatory insects, entire year classes of steelhead can disappear due to predation. Enter the fallen tree. The branches and trunks of laydowns provide hiding places that could be the most significant factor in the production of great year classes of steelhead in many of our slower and shallower forest streams. Steelhead rivers tending to be rather cold and sterile, those laydowns also provide nourishment for other aquatic invertebrates that steelhead parr depend on.

Trees are also used as perches for those same kingfishers and other predatory birds. And we humans use them to hide behind as we survey the pools for the sleek, powerful ghosts that visit there from time-to-time. Any unchecked population of living things soon throws the system out of balance, though we can choose not to kill our catch (and we rarely if ever should, in streams where natural reproduction occurs).

Rules that forbid clear cutting to the river’s edge just might be one of the most significant factors in the production of great year classes of steelhead. Just as significantly, such rules keep our steelhead rivers wild and beautiful. Can you have steelhead without trees? Yes—in big, relatively fast rivers running through regions with relatively cold climates. But trees never hurt, and obviously provide awesome benefits that should never be overlooked by anglers entrusted with the safety of the fishery.

 

 

 

 

 

  • Dave Rohde

    Damn astute observation!

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