Changing hatchery practices for Chinook salmon

GLG

Well-Known Member
Ecological implications of changing hatchery practices for Chinook salmon in the Salish Sea

Abstract
For over a century, hatchery programs have been used to subsidize natural salmon populations in order to increase fisheries opportunities and, more recently, to conserve declining natural populations. While an extensive literature has described the impacts of large-scale hatchery operations on freshwater ecosystems, less attention has been given to ecosystem interactions within the marine environment. We analyzed records of hatchery-released Chinook salmon in the Salish Sea to assess temporal and spatial changes in hatchery practices since 1950, with the goal of identifying potential implications for ecosystem dynamics and conservation efforts in the region. Over the past 65 yr, we found significant changes in the size and time at which juvenile salmon are released, resulting in decreased diversity of these traits. Research suggests that predation on juvenile salmon by other fish, avian, and marine mammal species could be size-dependent, and our results indicate that current hatchery practices are releasing Chinook salmon in the size range preferred by these predators. With current marine survival rates at chronically low levels, and increasing demand for hatchery subsidies, it is important to consider how modifying existing hatchery programs intended to reduce homogenization may promote more natural marine food web dynamics, with potential benefits to both hatchery and natural Chinook populations.

https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1002/ecs2.2922

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Good research paper, and it appears to align with pressures for SEP to make changes to their programs. We are certainly seeing greater degree of experimentation regarding release strategies, and seeing some interesting results suggesting there are ways to trick predators. I also think the seal cull proponents need to consider that "avoidance" is indeed a viable approach. That is we can do things like remove log booms from areas they are used as haul outs by seals that have become out-migrant smolt predator specialists for example. Another is we can amend release timing or hold smolts in sea pens to reduce predator interaction. We can also amend hatchery programs to release smaller less fed smolts. It will be very interesting to see what happens this coming summer with Robertson Chinook. This brood year return was one where over half were released early due to a pump failure. Those small unfed Chinook were feared to have lower survival....but, early indication is we had a strong return this year of 3 year old fish, a head scratcher. Generally a strong showing of 3 year old fish is an indicator the main return at age 4 will be decent. There are many other factors at play, so this is just guess work on my part...but an interesting theory to follow next summer to see if the unintended consequence of an early release was actually positive. Some of Dr. Trites Grad Student's work on the Qualicum also demonstrated that seals targeted the larger coho out-migrants released from the hatchery over the much more abundant but smaller Chinook out-migrants....size does matter when you are a predator....big smarty or small smarty.
 
This information of the improving and evolving fish hatchery programs needs to be shared more with ENGO's and the growing numbers of anti-hatchery staff at DFO. Many of the anti-hatchery concerns are based upon hatchery technology and practices from the 1970's, things have greatly changed and improved since then. We need to pressure DFO to modernize their hatchery programs to help the SEP to be more successful.
 
It would be great to see more "natural" rearing techniques utilized to produce fish of more natural size and robustness. Research like this shows some pretty simple means to get larger improvements in our enhancement efforts, and specifically to improve the overall return rate of released hatchery individuals. It will be very interesting to see what happens with these coming Robertson Creek fish - potentially a very fortunate and informative mistake! Larger smolts tend to return at a younger age as well, as their larger body size provides a competitive advantage over their cohort, which, oddly / generally, leads to them coming back to the river as smaller-bodied 3 yr olds, because they are the cream of that crop, and can compete on spawning grounds with the older cohort, as Jacks. However, those large-bodied chinook we all desire are generally the smaller individuals when they leave for the ocean, choosing to remain at sea for longer and increase their body size, allowing them to be more competitive when on the spawning grounds (more years at sea, more lbs to gain, but also a greater chance of being killed). It would be great to see SEP begin to test these theories rigorously in the larger production facilities like Chilliwack, who have a dedicated and invested staff.
 
that's where I hope parental-based tagging could take us...
 
We need to pressure DFO to modernize their hatchery programs to help the SEP to be more successful.

It would be great to see SEP begin to test these theories rigorously in the larger production facilities like Chilliwack, who have a dedicated and invested staff.

Why are we assuming that SEP is already not doing this? or experimenting?

Also the C/V hatchery has some of the highest marine survival rates. The hatchery survival is actually higher than the wild counterpart survival.

Also one of the biologist that was out our meeting this year again mention that the lower mainland hatcheries were seeing higher survival then wild.

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SEP hatcheries do the best they can - but often make do wrt funding. The lack of funding affects capacity. Some of that capacity is the "extras". The ability to mark mas #s of fish - and mark "treatment" verses "non-treated" to see differences. So they are unfortunately often stuck w "tradition" verses cutting-edge science. The lack of being able to provide current and effective "measures of success" using mass marking to tell what worked and what didn't - has it's effects.
 
Not assuming they aren't, just saying it would be great to see it at a higher level of production as there is the planned increase in production. I know some research type rearing occurs at Nitinat - not sure about Chilliwack, but likely does? With the increased production, would just be good to see more variation in rearing. Might as well test a few theories when we can.

@wildmanyeah Curious to see the data on the higher than wild survival. Any resources you could pass along?
\https://www.psc.org › chinook-technical-committee › tcchinook-18-1-v1
The figure you showed is from this PSC report. It looks like those two stocks, Harrison and Chilliwack, are the hatchery stocks, used by the PSC as Late Run Fraser Chinook indicator stocks through the CWT monitoring and recovery programs. Curious why they only show the Smolt to 2yo survival, and not all the adult return age classes. My understnading is that the 2 year olds aren't even quite Jacks? I've always thought jacks were generally 3yo. I wonder if this is a consequence for the release of large bodied smolts, that return earlier? If that's how they are comparing the returns to wild chinook, then that could easily be considered as greater survival. But to only a certain life stage... and I don't have too much interest in catching 2 yr olds...

@searun Very cool read. Nice to see a good news story related to hatchery fish. Curious how opposed they are towards a single paper driving the science of hatcheries, but then are claiming that this single paper should change the practices... need the science to be science and (the tough part) get our managers to LISTEN to science.... if only....
 
You have to compare each individual stock. I was just giving one example that was told to us where hatchery chinook have higher survival then their wild counter part. Harrison river are wilds that have been captured and tagged. Chilliwack are tagged though hatchery. That is my understanding

Best go to the meetings as ask the DFO biologist for your areas specific stream information.

There is also planned increase in production but only at a few locations and it’s my understanding that it’s coming at the cost of reduced production in other areas. SEP has not been given any extra money or a budget increase.
 
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