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Author Topic: Purpose of snow fence weir?  (Read 701 times)

clarki

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Purpose of snow fence weir?
« on: November 20, 2024, 01:53:29 PM »

Over the weekend I was fishing a section of the Fraser River and came across two sections of snow fence staked into the river bed with rebar. The sections of snow fence were “C shaped and constructed as mirror images of each other with the backs of the “C” parallel to each other and about 20 ft apart.   The “C’s” of snow fence are doubled walled.

I’ve never fished this section of river in the fall before, but have in the spring, and have not seen this structure before. So either it’s the first year for it, or it’s taken down over the winter. It would take a significant amount of effort to pound in the rebar stakes and string the fencing.

The 20ft gap between the “C’s” aligns with a shallow channel that normally flows between two pools. (The water is higher in the pic so the channel isn’t evident)

I’m curious as to the purpose of the snow fence structure. One idea is that it’s to funnel chum up the channel to facilitate sucessful spawning. The other idea is that it’s a weir built by FN for fishing purposes.

Comments welcome.





« Last Edit: November 20, 2024, 02:03:07 PM by clarki »
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RalphH

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Re: Purpose of snow fence weir?
« Reply #1 on: November 20, 2024, 04:21:44 PM »

Weirs like that are sometimes used to trap fish in intertidal zones. As the tide floods fish move in behind the weir and as it falls some will be trapped in the concave side of the weir. As the river drops this time of year the fence may serve the same purpose.

Bottom left there appears to be a dead spawned out salmon and a redd.

My first thought is these may be to collect dead or spent fish drifting downstream to assess run size.
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clarki

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Re: Purpose of snow fence weir?
« Reply #2 on: November 20, 2024, 08:17:11 PM »

Perhaps…  While there were a number of dead chum caught up against the weir, there were a hundred times more resting in the shallows of the upstream pool.

I don’t think the purpose is run size enumeration based on gathering morts, but then again, it’s a good a suggestion as any.
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RalphH

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Re: Purpose of snow fence weir?
« Reply #3 on: November 20, 2024, 09:44:05 PM »

"Perhaps?". You asked for comments. I await a more plausible one from yourself or anyone else.

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clarki

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Re: Purpose of snow fence weir?
« Reply #4 on: November 20, 2024, 10:39:28 PM »

Yes. Perhaps…
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RalphH

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Re: Purpose of snow fence weir?
« Reply #5 on: November 21, 2024, 08:43:13 AM »

well perhaps we should consider these structures have been produced by the same extra-terrestrial visitors responsible for crop circles and similar phenomena  or perhaps you put them there yourself to vex members of fishing discussion groups everywhere! They could also be syruptious[sic] seal traps planted by the Specific Balance Pinniped Society or the related but not so related Specific Balance Marine Management people. Who knows what they could be?...perhaps
« Last Edit: November 21, 2024, 09:03:35 AM by RalphH »
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bj23

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Re: Purpose of snow fence weir?
« Reply #6 on: November 21, 2024, 09:17:50 AM »

well perhaps we should consider these structures have been produced by the same extra-terrestrial visitors responsible for crop circles and similar phenomena  or perhaps you put them there yourself to vex members of fishing discussion groups everywhere! They could also be syruptious[sic] seal traps planted by the Specific Balance Pinniped Society or the related but not so related Specific Balance Marine Management people. Who knows what they could be?...perhaps

Perhaps you both need a break.
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clarki

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Re: Purpose of snow fence weir?
« Reply #7 on: November 21, 2024, 11:22:48 AM »

well perhaps we should consider these structures have been produced by the same extra-terrestrial visitors responsible for crop circles and similar phenomena  or perhaps you put them there yourself to vex members of fishing discussion groups everywhere! They could also be syruptious[sic] seal traps planted by the Specific Balance Pinniped Society or the related but not so related Specific Balance Marine Management people. Who knows what they could be?...perhaps

Well, now you are just being silly!

Based on the shape of the structures, that maybe my description and pic didn't convey, I don't think the purpose is to collect morts. If it is, it's a very inefficient design as, as I mentioned, there are a hundred times more dead chum stranded in the upstream shallows than (that can easily be counted by a dead pitch survey) than there are caught up in the weir.

Appreciate the reply/comment. And while I think  your suggestion is plausible, I don't think it's likely. But I could be wrong. Hence...perhaps. 
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RalphH

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Re: Purpose of snow fence weir?
« Reply #8 on: November 21, 2024, 02:37:38 PM »

Well, now you are just being silly!



oh absolutely & I could go on.

However looking at the pic I would say the fence barriers have been damaged by water flow (notice some sections are droopy) so probably don't look quite as when they were constructed. They also appear to be patched (note the orange section). The sort of loop or C shaped section from the middle towards the far shore seems intended to coral something. The mid channel clear section may have been a place a net could be placed though usually weir traps for live fish would angle from near center stream to shore on either side with a purse of closed area for capture. Really don't know and I doubt anyone here does unless Dave has seen something like this before.

FWIW and as I am sure you know, enumerating morts is very common means of estimating run size. The usual method of having a crew walk the stream banks is inefficient, labour intensive and not pleasant work. Maybe someone was doing a trial on an alternate.

Maybe you should send the photo and particulars to DFO or even the Sto Lo or Cheam band offices as they may be aware what this was about.
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RalphH

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