Survival of Hatchery vs Wild Steelhead

silver creek

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I have no problem with the study.

The natural conclusion would be that wild fish can outcompete hatchery fish on a one to one basis and I totally agree with that.

However, I do have a problem if one concludes from the study that for every 1000 fertilized eggs from wild steelhead vs 1000 fertilized eggs raised in a hatchery, more wild steelhead will survive to adulthood than from the 1000 hatchery eggs. One cannot make that conclusion.

The reason is that there is a huge loss from those 1000 wild eggs. Relatively few even hatch. If steelhead egg to alevin stage in the wild is anything like salmon, one can use the following data. Only 15% of wild eggs reach the alevin stage while 90% of hatchery eggs survive to alevin stage. Even at the alevin stage, the wild fish have to then become fry and smolts so there is even more loss of the wild fish. For every 1000 wild eggs, only 5 become smolts.

http://www.aquacase.org/learning_docs/Salmon-Survival-Activity-Packet_Jan-2016.pdf

"Wild Coho salmon typically lay 2500 eggs in their gravel streambed nests, but only about 15% of those eggs will survive to hatch and become fully developed alevin...... Spawning and raising eggs at a hatchery dramatically increases salmon survival at the early stages,
often with 90% surviving through the alevin stage."

Screen Shot 2020-01-29 at 5.32.43 PM.jpg

So the hatchery raised eggs result in many, many, more smolts released into the wild.

Based on this evidence, for wild fish to compete with hatchery fish, there have to be way more wild fish returning to spawn because the efficiency of natural reproduction is so low. Said another way, even if hatchery fish are less competitive, hatcheries can overwhelm native fish.

Therefore, although wild fish can outcompete hatchery fish on a one to one basis, it remains important to maintain a healthy populations of returning native fish.

Secondly, when hatchery fish are released into a river system that holds native fish, even if they are less likely to survive; they still compete with the native fish and disrupt the native populations. Native fish outcompeting hatchery fish DOES NOT mean that the native fish do not suffer some deaths that would not have occurred without the stocking of hatchery fish.
 
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