The Road to Extirpation, by Bob Hooton

[searun]

Once again, aiming at one shinny penny isn't going to address enough of the issues facing Thompson steelhead declines. Removing the commercial and FN gill net fisheries will not address issues like predation. The science is becoming increasingly clear that marine mammals are a major contributor to at sea mortalities and the coast-wide observed trend of declining size at age of Chinook. Large Chinook are the preferred prey source of orca's - whom are now thought to be responsible for the size at age declines. Despite what you read in the popular press, the coastal population of orcas in increasing rather sharply in the past decade or more.

Thompson Steelhead are also similarly large high caloric energy sources for marine mammals at the early ocean entry stage and as returning adults. Steelhead DNA is often found in the scat samples of Killer Whales for example. Start reviewing the work of Dr. Carl Walters and Ohleberger et al https://www.pnas.org/content/116/52/26682

Dr. Walters has connected a strong correlation between increasing populations of marine mammals (pinnipeds) and dramatic declines in salmon, which also correlates with declines in Thompson Steelhead. Remember, the gill net fisheries pre-dated declines in Thompson Steelhead.

Pinning the tail on the gill net donkey is aiming too low and missing perhaps the most significant crisis of our time.

 

[agentaqua]

I'll keep looking Whitebuck. There may be a similar report out there somewhere. There was some discussion on bycatch in salmon fisheries on the
Recovery Potential Assessment for Chilcotin and Thompson River Steelhead Trout (2018) at: https://www.dfo-mpo.gc.ca/csas-sccs/Publications/SAR-AS/2018/2018_050-eng.html

(p.9): "Projections were simulated six generations into the future, which is 36 years for the Thompson DU (maximum age-at-return of six years), and 42 years for the Chilcotin DU (maximum age-at-return of seven years). A range of fixed exploitation rates from 0% to 25%, which span the range experienced in recent years, were simulated under each productivity scenario. The 0–25% is due to bycatch in salmon fisheries and through targeted sport fishing and does not include other sources of mortality."

Another resource - the Independent Review of the Science and Management of Thompson River Steelhead (2014) can be found at: https://www.fraserbasin.bc.ca/_Library/TR/steelhead_independent_review_march-2014.pdf

Intro: "Over the past 40 years with the adoption of more selective fishing methods, harvest mortality has dropped from around 70% to 10-20%. Over the same period, marine survivals have dropped so the net effect is a counterbalancing and steelhead productivity remains low."

Figure 4.4 on page 25 and Table 5.1 on page 47 are also informative.

Searun - as always - appreciative & respectful of your balanced & nuanced posts.

And as far as the intent of my posts goes - my intent is not to excuse gillnets (or lack of enforcement, monitoring, catch reporting, etc.) but rather bring another perspective on the complexity of making assumptions in how gillnets work (relative to size/species/timing) - and as Searun has pointed out seal predation is a very significant factor in declines. The situation is admittedly dire for Chilcotin and Thompson River Steelhead and I do respect the opinion, experiences and caring for these fish by the posters whom know the areas.

And today I'd also like to acknowledge the sacrifices made by our veterans so that we have the freedom of speech and thought that we are using on this forum.

 

[Dave]

I keep reading steelhead DNA has been found in pinniped scat .. why, I wonder has this DNA been not been further analysed to determine watershed origin? Given the fact Thompson steelhead smolts are so low in numbers, I have a hard time believing they are being targeted.

 

[searun]

I keep reading steelhead DNA has been found in pinniped scat .. why, I wonder has this DNA been not been further analysed to determine watershed origin? Given the fact Thompson steelhead smolts are so low in numbers, I have a hard time believing they are being targeted.

I'm not aware of efforts to resolve Steelhead stock composition in the DNA analysis - really depends on the researchers focus if they were simply satisfied to resolve the species.

As for impact of both out-migrant smolts and returning adults, the analysis Dr. Walters completed demonstrated 300,000 tonnes of consumption by pinnipeds. That is an extraordinary amount. Thompson Steelhead are most certainly in the mix. Further, if orcas are having a significant coast-wide (Alaska to California) impact on Chinook size at age....again, not a stretch to see steelhead in the mix. NRKW don't swim south in the winter, and Thompson Steelhead would be easy pickings migrating at a time when salmon runs have mostly already passed these forage areas....so, not a stretch to consider the role of NRKW in steelhead predation.

I think it is just too easy and convenient for us humans to blame the easy target (gill net fisheries). The problem isn't that simple. If you follow the decline trend for Thompson Steelhead, that decline really took hold in the early 1990's and the scientists of the day blamed "ocean survival" as the main problem. The Province also pushed hard on DFO to address commercial interception, but could never really answer why (if the problem was gill nets) we didn't see dramatic declines in the 1970's and 1980's during periods of very high commercial gill net fisheries. Conversely, human seal removals were stopped in the 1970's and populations rebounded in the 2 decades that followed which coincides with the precipitous decline in Thompson steelhead, and the beginning of the decline in Chinook.

Another problem is the impact of predation is more difficult to notice on relatively large populations of fish - Steelhead were a small population so we immediately noticed an impact, whereas Chinook were a larger base population during the build up of seal populations thus it took much longer for us to notice the impact. So basically as those populations start to decline predation plays an exponentially significant impact. Less prey available means predators have greater impact when removing the same number of prey from a population...simple math.

I do not want anyone to confuse me raising the impact of predation, as a reason to give fisheries managers a hall pass so they can maintain status quo on gill net fisheries - the main point I'm raising is if we put all our lobby efforts on convincing people that if we remove gill nets there will be a sudden recovery - that notion is simply nonsense and fails to look around to see the looming crisis of unchecked predation.

 

[Dave]

Good response Searun, thanks. I agree, gill nets are not the only issue but they do get the most attention.
This seems like a no brainer for some student ... find these steelhead DNA samples and determine stock origin. The fact this has not been done suggests to me the samples might not exist.

 

[Whitebuck]

Control the factors you can.
-Seal predation of outgoing smolts
-Ban all gillnets within our rivers