I believe Mr. Bison commented on this with some stats at the Steelhead Society presentation a few weeks ago.
He basically looked at the various trout that may emerge from eggs when they begin to hatch, and with figures, demonstrated that female fry from a female Steelhead parent have a higher likelihood to head to the ocean than others mating combinations/sex that hatch and emerge from the gravel.
He also mentioned that a key concept to increase the number of fish that will leave their natal system and head out to the ocean is to decrease the quality of their rearing habitat. He noted in systems with warm water conditions, minimal nutrients, and poor habitat, trout fry were more likely to leave and migrate to the ocean than systems that had good habitat, cooler oxygenated water, and lots of feed. Makes sense, as a fat steelhead is not going to take the risk to go out to the ocean, while a skinny, starved fish which is uncomfortable is likely to leave to look for better sources of food.
According to him the two biggest factors acting against Steelhead survival, and maybe other Salmonoid species is:
#1. In shore survival as they leave the estuary, move into the inner passage, as spend the 7-12 days needed to migrate up and make it to the open ocean and feeding. High rate of loss of fish (I think he had figures of up to 70%) and Mr. Bison hypothesized it was due to high rates of predation from pinnipeds. He stated if this was dealt with and solved, this would be the most important factor to assist us to help with steelhead survival and recovery.
#2. In the open ocean when it came to feeding, increased competition from rival species produced in hatcheries are leading to smaller overall size, lower survival rates, and when they do return, due to their smaller size, the salmonoids are producing up to 25% less eggs to lay. This increased competition comes from massive hatcheries out of Japan, Russia, other Asian systems, as well as our own systems found locally and in Alaska.
Please keep in mind I am providing a crash summary of studies he was telling us about that focused on Interior Steelhead. I would suggest much of what he states and suggested COULD be applied to other Steelhead species which are genetically different than interior stocks. It could be argued this is a theory which is being applied to a different group of fish, and thus, the speculation is incorrect, not factual, and not valid.
Dano
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Topic: 2019/2020 Chilliwack River winter steelhead fishery information & water condition updates (Read 25742 times)