On a post earlier this week I linked to the August 20, 2010 Watershed Talk — a publication of the Fraser River Aboriginal Fisheries Secretariat (FRAFS).
FRAFS staff (biologists) have written a decent summary of some of the shenanigans of this year’s sockeye forecasting: “Fraser Sockeye In-season Update – A good year for sockeye!”
Apparently some of my comments from earlier this year on effectiveness of some of the hydroacoustics and DIDSON-related counting methods may not be that far off. Some folks have tried to suggest that these methods are rather “exact”; others have suggested they are voodoo-science at best. I think my perspective is somewhere in the middle… decent tools for getting a rough idea of fish migration in deep, large, murky rivers.
The article outlines how Pacific Salmon Commission staff have discovered that the hydroacoustic counting methods utilized at Mission (in the lower Fraser Valley — Vancouver suburbs) has count discrepancies when compared to similar counting methods utilized a little ways further upstream at Qualark. The Qualark counts have been much higher than the Mission counts — they should be quite similarly related as it is the same river, with a few tributaries that sockeye may migrate up between the two counting stations.
While the estimates have been correlating fairly well for part of the run, Qualark has been generating slightly higher numbers than has Mission. However, in recent days that difference has grown significantly. Salmon Commission staff have analyzed the differences and are quite confident that the recent Qualark estimates are indeed correctly reflecting a stronger return (higher number of fish) than has Mission. They have adjusted all their in-season run size estimates and are currently assessing the reasons for the discrepancy. The width of the river at Mission, water depth, and fish behaviour are thought to be confounding the Mission hydroacoustic estimates.
“Adjusting in-season run size estimates” due to “confounding” factors (e.g. fish behavior… those darn fish, what are they thinking…) — I call that “making it up”. And, I don’t mean that as a shot at the professionalism or scientific acumen of folks involved… it’s simply that using electronic machinery to count biological critters generally results in estimates at-best.
And really, how can we be so sure that the “higher” returns being seen at Qualark are more accurate?
And what are the numbers informing in-season estimates… well… scale samples from test fisheries.
How many scale samples?
Well… here’s the charts from the Pacific Salmon Commission info sent out prior to conference calls:
Along the far left “Area/Gear” refers to fishing area — for example first line is Area 20 (just west of Victoria in Juan de Fuca) purse seine. The second column with the date and (n) with “n” referring to the number of scale samples (as far as I understand it… anyways). Then it’s % of Fraser sockeye. Then it’s the stock percentages broke out into the four groups made up of approximately 19 stocks, of which there are actually about 200 distinct Fraser sockeye stocks. Each acronym for those stocks is at the bottom broken down into the four groups.
How accurate is this info?
Well, on the Area 12 purse seine on Aug. 21 — approx. middle line of chart — over 26,000 sockeye were caught in that particular segment of the test fishery that day. And n=99?
Is one to surmise that 99 scale samples out of 26,000 fish caught gives a good representation of the stocks… hmmm??
On Aug. 19th there was an all time record catch in the Area 12 purse seine test fishery: 84,040.
Scale samples: n=99.
99 scale samples from 84,000 fish sounds like a very accurate prediction tool…
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My point here isn’t necessarily to take shots at the methods, as I’m not a pre-eminent fisheries scientists and would not be able to make better suggestions. My point is that the methods of “confirming” all these estimates (e.g. computer models, simulations, test fishing, scale samples, hydroacoustics, etc.) is by confirming Sockeye spawners on the spawning grounds.
Spawner estimates is a wonderful example of more — exactly as it says — “estimates”. There’s mark-recapture, counting fences, stream walks, helicopter overflights, and other wonderful estimating tools.
As much as many folks suggest this whole salmon thing is a very precise practice… it is far from it.
It is simply fancy tools that “kick-out” fancy estimates.
There are lots of good folks working hard at these estimates — however they’re still fancy estimates with absolutely no method to truly “confirm” that the models, scale sampling, test fishing, and so on are “accurate”.
Then throw in terms like “ecosystem-based management” — ever present in the Wild Salmon Policy — and I tend to call ‘bullshit’.
We simply don’t know… we’re trying hard to estimate; but really… we’re making it up as we go along… and that’s OK; it’s the defensiveness and insistence by those involved that we do know what’s going on…
well… i think this year is a fine example that we definitely do not know.