Sunday, 6 March 2016

Hatchery Problems

Hatchery Problems

Last week I sent along a summary of text, and two graphs, by Eric Wickham regarding opening up hatcheries to the private and volunteer sector. A list recipient sent me a good document regarding the arguments for not doing hatchery enhancement at all.

I have attached the document as I think you should read it. The main arguments are that hatchery fish – right from the get-go – are genetically distinct from local wild stocks. While hatchery fish, particularly chinook, have difficulty breeding, where it happens, this represents a dilution of wild genes.

The other main factor is that hatchery fish compete with wild fish for food in the ocean, and thus high levels of such fish can further reduce wild fish numbers. I think that netpen operations with triploid chinook – assuming this is feasible – can increase the numbers of chinook for Killer Whales and humans, in the interim period where wild stocks are improved, and then wind down the netpens.

What this means is doing the habit work in freshwater that is key to wild spawning success. Now that we are in the phase of climate change where hot dry summers are followed by heavy scouring winter rain, there are two issues. Most coastal rivers are so shallow by the end of August that chinook have trouble passing up, and in the past couple of years, I have witnessed even pink salmon, the smallest of the bunch, that need only a few inches to migrate up, be prevented from entering rivers.

Secondly, the drenching winter rains easily wash away all the spawned eggs, thus ruining a year’s spawn, followed by dry and hot that reduces flow and oxygen, while increasing temperatures. I have stood on gravel banks that in four days were scoured out to 12 feet deep, representing thousands of tons of good habitat almost over night in only one spot on a river’s run. Cabling of ‘woody debris’ is one answer to shooting a century of logging gravel out for good.

And lucky rivers like the Campbell that have dammed lakes above them can have their flow augmented in summer, but few rivers have headwater dams.  Having watched Toba Inlet be destroyed by commercial ‘Run of River’ power generation I am loath to suggest adding those in our wilderness lands anywhere.

An example of stellar channel work to vastly increase spawning habitat is on the section of the Taylor River alongside Highway 4 west of Port Alberni. Get out of the car and take a look along the decommissioned road that used to take you to the logging bridge over the river. Exceptional coho spawning habitat work.

So, have a read of the other side of the enhancement question.

Sorry, I could not get the PDF to attach to this blog. If you want it, send me an email.

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