Stormwater pollution in Puget Sound streams killing coho before they can spawn

[agentaqua]

https://www.seattletimes.com/seattl...d-streams-killing-coho-before-they-can-spawn/

 

[Dave]

Most likely this is happening in BC's Lower Mainland and on Vancouver Island as well and reinforces my contention coho and chinook have different freshwater habitat requirements.

 

[GLG]

No Dave you're jumping to a conclusion that is not supported by the evidence. Read the paper.
https://www.documentcloud.org/documents/4111834-Feist-Et-Al-Pre-Print-2017.html

We know where the problem is with the decline of coho. It's the first few months when the smolts enter the ocean. This effect is with both hatchery and wild coho. In the past our hatcheries had a smolt to adult return rate of 15% , now it is around 2%. The question that is being investigated currently is what is causing this. Fix that and our coho populations will rebound.

 

[Derby]

Steelhead as well..

 

[SpringVelocity]

Most likely this is happening in BC's Lower Mainland and on Vancouver Island as well and reinforces my contention coho and chinook have different freshwater habitat requirements.

They do? Do tell.

 

[agentaqua]

Agree w Dave that CH & CO juvies have different habitat requirements - however, the hypothesis that the FW habitat is the limiting factor (verses another impact) for CO is still unsupported w info/data.

 

[Dave]

No Dave you're jumping to a conclusion that is not supported by the evidence. Read the paper.
https://www.documentcloud.org/documents/4111834-Feist-Et-Al-Pre-Print-2017.html

We know where the problem is with the decline of coho. It's the first few months when the smolts enter the ocean. This effect is with both hatchery and wild coho. In the past our hatcheries had a smolt to adult return rate of 15% , now it is around 2%. The question that is being investigated currently is what is causing this. Fix that and our coho populations will rebound.

Ocean survival is of course the biggest factor in adult coho returns (along with all other anadromous species) but having mortalities before spawning limits genetic diversity and obviously results in fewer juveniles.
I think the days of 15% survival are long gone.

 

[Dave]

Agree w Dave that CH & CO juvies have different habitat requirements - however, the hypothesis that the FW habitat is the limiting factor (verses another impact) for CO is still unsupported w info/data.

I never said freshwater habitat is the limiting factor for coho production, but it obviously has a substantial impact when fish die before they spawn.