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Author Topic: Jet Boats Affect on Fish  (Read 7221 times)

Trout_Bum

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Jet Boats Affect on Fish
« on: November 15, 2011, 06:56:31 PM »

I was killing some time watching youtube videos of guys going up the Upper Pitt in Jet boats. Some of the water they were going through was extremely shallow. It sure seems the water pushing out of the jet must be at extreme pressure to generate the high speed of the boat.
I wonder if the jet nozzle can affect either spawning fish or eggs in the gravel. Anyone ever see any impact studies?
The technology is great, but I worry that this makes accessing true wilderness just too easy.......kinda like a water version of an ATV.

Trout Bum
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Sandman

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Re: Jet Boats Affect on Fish
« Reply #1 on: November 15, 2011, 07:59:56 PM »

I was killing some time watching youtube videos of guys going up the Upper Pitt in Jet boats. Some of the water they were going through was extremely shallow. It sure seems the water pushing out of the jet must be at extreme pressure to generate the high speed of the boat.
I wonder if the jet nozzle can affect either spawning fish or eggs in the gravel. Anyone ever see any impact studies?
The technology is great, but I worry that this makes accessing true wilderness just too easy.......kinda like a water version of an ATV.

Trout Bum

This was hotly debated years ago when jet boats first became popular and the upper Pitt was a prime case as were some Vancouver Island rivers.  It is also widely discussed in Washington State.  In my opinion, (and it is just that... my opinion... as I have not conducted any studies, nor am I quoting any, although I have participated in more than a few discussions on this topic over the years), the water coming out the pump nozzle is sure to cause considerable disturbances, both in the gravel, as well as moving the salmon off the redds, at least temporarily, as the boat passes. If you have seen the large holes dug at boat launches from "power loading" jet boats onto trailers, you would know what I mean. Therefore, there has to be a possibility of the jets scouring gravel off the top of the redds and possibly harming eggs or alevin, if a boat is driven over water of say... less than a foot deep. Now in this case, the size of the gravel used by salmon for spawning would appear to be easily moved by the force of the water from the nozzle, but whether damage is done to the eggs would depend on how deeply the eggs are buried. It would seem that Pink salmon redds would be the most at risk as they utilize the shallowest water, smallest average size gravel, and make the shallowest redds, whereas Chinook redds would be the least vulnerable as they use the largest average size gravel and bury their eggs the deepest, and they usually spawn in water of a foot or more in depth.  The other species would probably fall somewhere in between these two extremes.  The mitigating factor would seem to be the timing of the jet boat's run in this shallow water (between spawning season and the spring when the eggs hatch), and their chosen path over the redds.  Since many of the jet boats are used by fishermen, the former is highly likely to cause an impact, however, except perhaps during a pink run when redds are everywhere, most jet boats use a path that takes them over a small percentage of the redds (the best path for a jet boat is usually over water that is least suitable for spawning).  As the use of Jet boats increases, so will their impact, and like any user, the solution is education.  Just as a walk and wade fisherman needs to be educated on how to wade across a river so as to impact the redds as minimally as possible, so too do jet boat users need to be informed as to their impact and how best to minimize it.
« Last Edit: November 15, 2011, 08:11:04 PM by Sandman »
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Dennis.t

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Re: Jet Boats Affect on Fish
« Reply #2 on: November 16, 2011, 01:44:38 AM »

Jet boat use on the Upper Pitt has been a controversal topic for a number of yrs now.There was a news segment on the issue on Global,a couple of yrs ago.It showed a jetboat that had crashed and sunk in the middle of the river.Apparently it is a changelling river to jetboat and a few have ended up on the bottom of the river.This cant be good for the river. I guessing there is user impact at play here.Ive also read in other articles about bank erosion from the waves caused by passing jetboats where they are used.Another theory is that when a jetboat passes over stale fish lying in a pool it will stir them up and cause them to bite.Im not an expert as i have never been to the Upper Pitt and dont think there is any scientific studies ever done.User impact may never be known.Just some thoughts to ponder...
« Last Edit: November 16, 2011, 02:43:39 AM by Dennis.t »
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Geff_t

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Re: Jet Boats Affect on Fish
« Reply #3 on: November 16, 2011, 07:15:40 AM »

I know there would be some local guides that would disagree but I think there needs to be a boundry for jet boats on certain rivers like the Upper Pitt. If not for the safty of the boat but for the fish. The last thing these fish need is to be stressed by a jet boat screaming by over their heads. This is one of those last rivers that is not hatchery enhanced so it needs to be protected.
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StillAqua

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Re: Jet Boats Affect on Fish
« Reply #4 on: November 16, 2011, 09:52:46 AM »

They did a study in New Zealand in the 70's showing the pressure wave from jet boats could kill incubating eggs.
http://www.tandfonline.com/doi/pdf/10.1080/00288330.1975.9515566
Probably a lot of other negative effects too.

"The passage of jet boats through spawning areas can kill salmon eggs buried in the river bed. By using a jet boat on the Ashley River the pressure gradients created in a redd were determined. At the maximum boat speed investigated (11 m.s-1) gradients up to 9.32kPa.m ' were recorded. The induced water velocities through the gravel were then estimated from the equation of motion and reproduced in a gravel-filled tube in the laboratory. For the test conditions discharge velocities ranged from 0.18-0.3 m.s-1. Studies of the effect of these flows on salmon eggs revealed fatality rates of up to 40% at their most critical stage on the ninth day of development."
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Dennis.t

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Re: Jet Boats Affect on Fish
« Reply #5 on: November 16, 2011, 11:36:09 AM »

I had a look at the mentioned You tube videos.A few, depict jetboat use in very shallow water on the Upper Pitt.One of the boats even becoming stuck.Not sure how much boat traffic is actually up there. Ive never been and dont know anybody who goes up there.Sure looks like a beautiful river in awesome surroundings.
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GordJ

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Re: Jet Boats Affect on Fish
« Reply #6 on: November 16, 2011, 09:44:38 PM »

Mine was one of the boats in the Global piece. I have watched that piece over and over and every time I think about it I get mad. It was a terribly inaccurate article and made claims that were completely wrong and untrue. For one thing, the wrecked boat did not crash and sink in the middle of the river. They backed off the bank and the reverse jammed and they had no forward. They drifted down into a log jam and tipped over. This could have happened anywhere, there was no operator error or inexperience involved. Don't get me going on the rest of the article.

And remember there have been more pickups and logging equipment in the river than jet boats over the years.

They talk about bank erosion but one freshet causes way more erosion in one spring than all the jet boats in BC could in one year. The banks, by and large, are river rock banks and as such are resistant to wave related erosion but the river runs huge when it is in freshet and cuts new channels every year.

Very few boats ever run in less than a foot of water and where they are shallow it is usually the main channel and is not spawning habitat. I know that jets can run shallow but what I am saying is that most boaters want water under them. Right now the water is so low that 90% of the boats around can't access more than the bottom 5/6 km's.

Geff says that the fish don't need a boat screaming over their heads but ,again, we are running in the deepest, fastest water mostly and not in spawning habitat. Your comment about the lack of hatchery enhancement would be interesting to the staff at the Courbould Creek hatchery because according to the internet "They release 800,000 Coho, 200,000 Chinook, 1,000,000 Chum and 20,000 Steelhead in Pitt Lake and the surrounding lakes and rivers."

StillAqua, didn't that study indicate that the damage to the eggs peaked on the ninth day and there was very little impact on either side of that time? I read that report a while ago because I thought I should find what impact I am having when I boat. As I remember the water in the study was around 12" and I couldn't find any information on the river to compare their conditions to the Pitt but I think the Pitt is a bigger, faster river than where they did the study. Obviously, or maybe not, more water should mean less impact.

Sandman makes some very good points and education should be available so that all boaters (not just fishermen) can minimize their impact. Unfortunately there is nothing available that I am aware of.

Obviously the boats will have some impact but I really don't think it is particularly significant.

I keep seeing that it is crowded at times on the river but I don't think I have ever seen more than a dozen boats on the busiest day but I always hear about how it is too crowded with 20-30 boats. I would guess that most of the times I have been up there I would see about 5-6 boats but I don't go during salmon season. I think a lot of the information about this place is put out by people that have an interest in restricting access to their customers only. Lots of times we will be the only boat on the river that is fishing.
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Dennis.t

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Re: Jet Boats Affect on Fish
« Reply #7 on: November 17, 2011, 09:52:44 AM »

Thanks for posting. Great insight and informtion on the Upper Pitt.If I remember correctly it was Danny Gerak that was interviewed for the Global piece.Over the yrs,I have seen him on the news or read about his fight to protect the Upper Pitt.Can remember him on Global showing bank erosion that was exposing an old garbage dump that the loggers left behind.Also something about gravel mining.A true champion for the river bringing the enviromental issues facing the Upper Pitt to the forefront.Not sure if hes still up there?Like i said before,sure looks beautiful up there from the you-tube videos.We are truely blessed to live in B.C.
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StillAqua

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Re: Jet Boats Affect on Fish
« Reply #8 on: November 18, 2011, 05:26:53 AM »

Mine was one of the boats in the Global piece. I have watched that piece over and over and every time I think about it I get mad. It was a terribly inaccurate article and made claims that were completely wrong and untrue. For one thing, the wrecked boat did not crash and sink in the middle of the river. They backed off the bank and the reverse jammed and they had no forward. They drifted down into a log jam and tipped over. This could have happened anywhere, there was no operator error or inexperience involved. Don't get me going on the rest of the article.

LOL......Sometimes I wonder about our media and what we should believe...I don't know anyone familiar with a story who hasn't complained they got so many facts in stories wrong or spun them in certain ways to make them more sensational.

StillAqua, didn't that study indicate that the damage to the eggs peaked on the ninth day and there was very little impact on either side of that time? I read that report a while ago because I thought I should find what impact I am having when I boat. As I remember the water in the study was around 12" and I couldn't find any information on the river to compare their conditions to the Pitt but I think the Pitt is a bigger, faster river than where they did the study. Obviously, or maybe not, more water should mean less impact.

Egg mortality peaked about 9-10 days at 60% at the highest pressures and it dropped off to about 5% after 2 weeks. There isn't much other data that I can find but it's probably a good precaution to restrict all power boating traffic during spawning and for a few weeks after in sensitive areas and streams. I don't know if the Upper Pitt fits the bill but I can think of a few in the Shuswap that could use some protection.
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River Fisherman

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Re: Jet Boats Affect on Fish
« Reply #9 on: December 12, 2011, 06:43:56 PM »

I fish the Upper Pitt since the 90`s and this issue has been discussed to death. Yes - some boats and guides go further than the first 5 K`s, but less than a handful goes MUCH further into real shallow and challenging water. I do not believe that this is a real danger to fish. Way too much used by certain interest groups and users. As some of you stated, most boats only fish the first few K`s. When going past the 2nd canyon via helicopter, the fishing is out of this world with huge fish in untouched waters. No sight of any jet boats and lots of fish - LOTS, despite many boats operation in the lower part of the upper Pitt. Would be nice to keep the politics out of some discussions, although I am all pro fish protection and enviro.
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