Mortality =40%
- Thread starter Chaz
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Are they claiming this for non-stocked streams also? If so then I would have to say that is complete BS. The natives on the L Lehigh, Spruce, and others are hardy fish that are not going to keel over and die. If predation is taken into account then it may be as high as 20-25%, but frankly I don't believe the 40% claim.
Now for stockies, I can see the number being close to 40% because they simply don't have the smarts of native stream-bred fish. They have been raised from fingerlings being fed fish-chow, which completely ruins their natural instincts.
Now for stockies, I can see the number being close to 40% because they simply don't have the smarts of native stream-bred fish. They have been raised from fingerlings being fed fish-chow, which completely ruins their natural instincts.
Wulff-Man
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I would think mortality on stocked streams would be closer to 90%, and it would be closer to 100% if they didn't stock streams with decent wild trout reproduction. So ryguyfi has a good question. Is that an average that includes all streams, from Class A to Approved Trout non-reproduction streams? If so, it doesn't tell us much. Or is it just for wild trout streams (which could be defined in different ways)? If so, 40% would be surprisingly high, don't you think?
tomgamber
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So if I they stock a stream with three hundred fish and 100 guys catch and eat 3 each...its a 40% mortality. If I go to a wild stream and catch and release 100 fish...its a 40% mortality rate? You better be more specific Chaz...
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I do not think that 6-12 months of conditioning in a hatchery is capable of eliminating thousand or millions of years of instinctual behavior. If a creek has a sufficient food supply, stocked trout are able to survive the same as stream-born trout. It would only be in the circumstances of a relatively infertile stream, with a high rate of competition from other fish, where the learned behavior of expecting hatchery pellets to descend from the heavens at 900 AM and 430 PM would be fatal to the stocked trout in greater proportion to wild fish. Anyone who has fished for stocked trout in streams with significant hatches knows full-well that hatchery raised fish learn how to feed on naturals very quickly.
Padraic
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If that's for all year classes it sounds pretty low. I mean trout lay thousands of eggs. A couple of the better streamers to carry are the baby brown and baby brook trout patterns. So obviously the YOY get eaten up in good numbers. Besides that, there are herons and king fishers, mink, water snakes... lots of stuff like the taste of trout.
I also think that the mortality on most stocked streams has to be a lot higher than that. Clarks Creek was getting 10K trout year after year for a good while there. If 6K of those trout held over every year, the stream would be packed with trout.
I also think that the mortality on most stocked streams has to be a lot higher than that. Clarks Creek was getting 10K trout year after year for a good while there. If 6K of those trout held over every year, the stream would be packed with trout.
I think this may be accurate. I would guess on quality wild brown trout streams mortality is probably about 20% and on stocked streams that get warm in the summer it's probably about 99%. I think on most mountain brookie streams the life expectancy of a brookie that reaches fingerling size is only about two years.
cdogedoger
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does anyone have the link for this topic. checked the fish and boatcomm. web site and couln't find it.
thanks
john
thanks
john
bigjohn58
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Mortality on a lot of stocked streams are no way near 90% after finding out how many survived on Kettle Creek this year. I'm guessing stocked trout its more around 75% and half of that is from people harvesting them and the other half is weather related or preditors. The stocked trout are not as dumb as people think.
MKern
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So, for the sake of argument, let's say 90% of trout die on stocked streams. For and AVERAGE of 40% overall death rate that means on wild streams (which are less abundant than stocked streams) only about 5 % of fish die every year.
But thats is if they figure and average of all streams, and not specific data from each stream (which is probbaly the case).
But thats is if they figure and average of all streams, and not specific data from each stream (which is probbaly the case).
MattBoyer
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I would guess that since most migrating salmonids lay thousands and thousands of eggs just to have one or 2 grow to maturity, that 40% not making it to reproduce would be a low number, if that is indeed what we are talking about. 40% per year sounds about right. I'm horrible at math and stats, but that seems to me to be how nature works. It takes a lot of lives to make one long life. Once again, I'm not a statistition, in fact, I'm pretty sure I can't even spell the word, but that's my $0.02 anyhow.
Boyer
Boyer
Wulff-Man
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It's true that on some good quality streams a greater proportion of stocked trout will survive, but on the vast majority that can't support or barely supports trout life through the summer, nearly all will die. That's why I said 90%, because I was including good quality streams in the mix. I think the major factor is water temperature / dissolved oxygen, followed by predators and food supply. It's not so much the stocked trouts genetic ability to cope out of the hatchery, but that does play a pretty big part in wild trout streams. But KIMIHNIWITA.
The thing with Chaz's statement though is that we don't know what it applies to, as far as the streams that are included. I'm not even sure what "mortality" means, after reading Padraic's and Matt's responses. Is it 40% of all eggs laid (then it definitely is too LOW)? Is it 40% of all trout stocked? Is it 40% of all trout older than 1 year? Bigger than legal size? ........
Short answer to Wulff-man is "YOY wild trout to adult wild trout")
I vould venture to guess Chaz is talking about...or rather The PF&BC, wild trout streams. Based on data colected during surveys of multiple year classes and over a perios of years, they can determine with a degree of certainty how many trout die off from each subsequent year classes. (within the survey area of course)
In addition, by comparing streams where harvest and fishing are allowed, to others that are closed to the public, they can gather both forms of data and average them.
I don't believe they are suggesting anything about stocked trout because thye stock them with the intent to harvest them...except where they are stocking fingerlings.
Buy as many suggest, I'd like to see the numbers.
Chaz's post is like a Bizarro world newspaper where there is a headline and then the story is just a re-statement of the headline with no more detail than the headline....imagine a newspaper like that... pages and pages of headlines, with no stories...so we make the stories, right or wrong, fact or fiction.
America...what a great city!
Maurice
Wulff-Man
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I think that makes sense, Maurice. When you think about it, a wild brown trout's full life span is what, 5 to 10 years? That would mean that between 10 to 20% per year would die from old age alone (assuming the "birth rate" - meaning survival rate to YOY - is pretty consistent from year to year). So about 25% die from predation and disease, etc. And most of those are probably the younger ones.
tomgamber
Well-known member
Mo, I wouldn't venture to guess or assume anything about this...chaz threw this statement out here, like a handful of hatchery pellets. Well, the pellets we gobbled up from every direction as he knew would happen. Now Chaz has gotten some opinions and its time for him to tell us what the heck he is referring to. C'mon Chaz, that was like one of those trolls from the old board. Let us in on what, exactly, that statement means.
The average annual total mortality reported by the PFBC at the trout summit was 60 to 65 percent depending upon whether or not one was speaking about freestone or limestone wild trout streams. Total mortality is comprised of two components: angling mortality and natural mortality. It is generally calculated for fish that are age 2 and older. although age 1 fish are sometimes included. Young-of-year fish are not included. Additionally, the statewide wild trout creel survey revealed that the angling mortality component of the average annual total mortality was on average around 4 percent. Given the low angling mortality in general on a statewide basis in wild trout streams, is it any wonder why so few wild trout streams in Pa (except for the major limestoners and a very few freestoners) respond favorably to special regulations designed to increase the abundance and size distribution of the fish? One scientific paper cited in the wild trout creel survey report suggested that an angling mortality rate of 50% is needed to see a favorable response to special regs of the type mentioned above.
Hi Mike,
Thanks for clearing that up...Please define what a "favorable response" to special regs means. Would that mean an increase in biomass? or an increase in larger or adult fish?
My view is that if a stream has zero harvest it relies on incidental mortality from angling and natural mortality (probably near the 50% you mention) to produce the carrying capacity.
How does increased harvest improve the carrying capacity?
Or rather, do you feel that the studies indicate the "allowable" harvest could reach 50% before having an impact on the streams favorable response?
Maurice
Here's a quote from a Fisheries Manager in Virginia in their publication Virginia Trout Guide:
"The major management problem associated with Virginia streams appears to be excessive fishing pressure on many of the more popular wild trout streams resulting in over-exploitation.
In MD, the state-wide, general regulations on wild trout streams is 2 fish per day. That's not a SPECIAL regulation, it's the general regulation on wild trout streams. Then there are also C&R regulations on certain wild trout waters.
In Shendandoah Park, some streams are C&R, the others are 2 fish, 9 inch limit (as compared to 7 inches in PA). When I fished there, 8 inch brookies were very common.
Most of Yellowstone Park is managed as C&R.
PA is becoming isolated, out of the mainstream of fisheries science. Maybe everyone else has it wrong, and the PFBC has it right. You have to decide that for yourself.
"The major management problem associated with Virginia streams appears to be excessive fishing pressure on many of the more popular wild trout streams resulting in over-exploitation.
In MD, the state-wide, general regulations on wild trout streams is 2 fish per day. That's not a SPECIAL regulation, it's the general regulation on wild trout streams. Then there are also C&R regulations on certain wild trout waters.
In Shendandoah Park, some streams are C&R, the others are 2 fish, 9 inch limit (as compared to 7 inches in PA). When I fished there, 8 inch brookies were very common.
Most of Yellowstone Park is managed as C&R.
PA is becoming isolated, out of the mainstream of fisheries science. Maybe everyone else has it wrong, and the PFBC has it right. You have to decide that for yourself.
