Culling

[Stone_Fly]

Call it what you want, but when we harvest wild trout in the interest of culling say to allow some bigger fish to be produced, it doesn't work for at least 2 reasons, first if you take fish larger then the size limit, which is by law what you have to do rather then take only fish smaller then 7 inches, you won't get the larger fish you want in part because of over harvest and in part because of the constraints nature puts on streams.
Second the fish cull their own populations by cannibalism and by the bigger fish keeping the best lies within the habitat. This causes a die off related to the health of the fish, but it doesn't change the food chain in the stream because the food chain is controlled by habitat, not necessarily predation. Predation has a role, but it is overstated by anglers.
Third if culling were to be successful then you'd see changes within the food chain that could easily be quantified by surveys and controlled by predation, and we just don't have any evidence that this takes place in our streams.
Humans are the only wild card that can control a fisheries population, they either harvest all the legal trout or if no one ever fishes a particular stream they don't harvest fish. So releasing nearly all the wild fish you catch is going to guarantee the health of the population. Fish population can't crop themselves and no one has ever shown that they can.

 

[OhioOutdoorsman]

Good points stonefly.

On your first point, I agree. We'd have to harvest smaller fish. I'm not saying through 5" brook trout on the bank. But what about experimenting with a slot limit...like one trout between 7-10" a day.

On your second point, definitely true for browns.....I'm not sure about rainbows and brookies as from my understanding they are mainly insectivorous and invertabrate consumers, even when they reach a large size. Also if you remove that larger predator you are not only removing a large fish, but also its affect on the population.....the effect of that fish eating one or two dinks a day....so more small fish will be around and subsequently less food for larger fish in the stream and so on and so. Its too complex of an interplay to reason out.

I'm not understanding your third point.

If I were the PFBC, I'd do this, which we may already have done:

Go ahead and experiment with a few wild trout streams, and change them from the standard regs to completely C and R. Then measure not only the number but size of fish. I think you might see no change in the biomass, but a decrease in the average size of the fish.

All I'm saying is its worth looking into, if it hasn't been already. We can argue what is logical or illogical forever......lets experiment and measure.

Anybody know of any studies along these lines?

 

[Maurice]

OhioOutdoorsman wrote:
Good points stonefly.

On your first point, I agree. We'd have to harvest smaller fish. I'm not saying through 5" brook trout on the bank. But what about experimenting with a slot limit...like one trout between 7-10" a day.

On your second point, definitely true for browns.....I'm not sure about rainbows and brookies as from my understanding they are mainly insectivorous and invertabrate consumers, even when they reach a large size. Also if you remove that larger predator you are not only removing a large fish, but also its affect on the population.....the effect of that fish eating one or two dinks a day....so more small fish will be around and subsequently less food for larger fish in the stream and so on and so. Its too complex of an interplay to reason out.

I'm not understanding your third point.

If I were the PFBC, I'd do this, which we may already have done:

Go ahead and experiment with a few wild trout streams, and change them from the standard regs to completely C and R. Then measure not only the number but size of fish. I think you might see no change in the biomass, but a decrease in the average size of the fish.

All I'm saying is its worth looking into, if it hasn't been already. We can argue what is logical or illogical forever......lets experiment and measure.

Anybody know of any studies along these lines?

The BTEP Brook Trout Enhancement Program...in its second season by the F&BC is designed to determine carrying capacity with C&R. It will provide the results for comparason to previous years that allowed harvest.

 

[JackM]

Before we know the results, will anyone go out on a limb and say whether they think the program will provide data that is valid from a scientific standpoint? I will abide by the objective findings-- will the rest of you?

 

[Stone_Fly]

All trout pray on other fish, this is I believe more true of brookies then the others as the conditions they live under tend to be more severe. Though I know of a few limestone streams that one would think that the brookies would have a more diverse diet, the fact that they lack bright colors indicates their diet is mostly fish. In fact when I fish these streams under most conditions I try streamers first, because the trout there pretty much ignore the bugs unless there is a major hatch. I know this doesn't fit with what most people would believe, but it is a fact on certain limestone streams.
As to my third point what I'm saying is that trout barely put a dent in the macro-invertebrate populations of streams if they did, we'd see it. What we do see is fluctuations of forage caused by natural causes, like floods and droughts. These of course can devastate a fish population too. So what I'm saying is that trout don't become stunted, if a population is small in size, that is mostly fish under 10 inches, it is because of factors not related to the forage base, unless in some cases a stream has no forage base as is the case of some AMD brookie streams. Even in some of them there are brookies up to 15 inches, which is a nice trout no matter what species it is for PA.
So culling the fish doesn't work in the sense that humans can't manipulate a population by keeping only certain sized fish and putting all of the other fish back. Nature controls it; nothing man can do to change things except improving the habitat. Improve the habitat and you'll start to see larger fish, or make it C & R and the population will adjust to some variation of size based on the available habitat.
Does that make sense?

 

[shipnfish2006]

I fished on 2 of those BTEP streams last year and I've been pretty impressed at the fish I've caught. The amount of 7-10" brookies was much greater then in the past and also compared to a couple of nearby open regulation wild streams.

I look at the whole thing as one big ecosystem. The trout can only get as big as their surroundings will allow. If the food is there whether it be bugs, invertebre, or other fish. If the stream doesn't have proper cover to keep the fish from the eyes of predators then the fish will max out in that particular water and never reach the 12+" range, when looking at brookies.

Also if you look at a pond with a lot of fish in it, the more the fish spawn and increase in numbers the lesser the forage and protecting habitiat available for all of the fish. Eventually the fish will start a generation like sequence and they never have the chance to reach their full potential.

From what I've noticed the biggest brookie streams are streams that have been hit by droughts from time to time and a lot of fish died off and as the stream repopulated the ones that survived the drought grew to a pretty good size because they had a lot less competition for forage and cover, but as the numbers have gone back up the sizes have started to go back down.

 

[CaptMatt]

OhioOutdoorsman wrote:
Good points stonefly.

On your first point, I agree. We'd have to harvest smaller fish. I'm not saying through 5" brook trout on the bank. But what about experimenting with a slot limit...like one trout between 7-10" a day.

On your second point, definitely true for browns.....I'm not sure about rainbows and brookies as from my understanding they are mainly insectivorous and invertabrate consumers, even when they reach a large size. Also if you remove that larger predator you are not only removing a large fish, but also its affect on the population.....the effect of that fish eating one or two dinks a day....so more small fish will be around and subsequently less food for larger fish in the stream and so on and so. Its too complex of an interplay to reason out.

I'm not understanding your third point.

If I were the PFBC, I'd do this, which we may already have done:

Go ahead and experiment with a few wild trout streams, and change them from the standard regs to completely C and R. Then measure not only the number but size of fish. I think you might see no change in the biomass, but a decrease in the average size of the fish.

All I'm saying is its worth looking into, if it hasn't been already. We can argue what is logical or illogical forever......lets experiment and measure.

Anybody know of any studies along these lines?

I wrote a little blurb about this on another thread. Florida does that with snook that have taken a serious beating in the previous years. They have 2 things going bad for them, they are a blast to catch and they are great to eat. So FL introduced a slot limit from 27-34 inches with a tail pinch, tail pinch as of this year. It proves effective from what I understand but still too early to tell numbers wise. It makes perfect sense though.

 

[OhioOutdoorsman]

Stonefly,

What you say makes sense for limestoners. On limestoners, where forage base is clearly not the limiting factor, I doubt that any sor of culling/slot limits would make any positive difference in the size of the fish.

Don't know about the brookies being carniverous......I have a fisheries biologist friend who tells me otherwise.....probably depends on the stream. I would think on infertile streams trout would have to eat more non-insect food. If we're talking about a bunch of stockers that were just dumped in a river, exceeding its carrying capacity, I definitely agree that they hammer small fish (and streamers) hard.

Now if we're talking a wild population on infertile freestoners, I think the jury is still out. I hope the BTEP works (proving my theory wrong) and look forward to the results. Nice to know its a study and that enhancement hasn't been assumed to occur.

 

[Wulff-Man]

Does anybody know (or do you have opinions on) whether the streams that are in the BTEP were selected because of the likelihood that their populations could thrive (I guess that means fertility and habitat, maybe also because there was a fair amount of harvest before the program), or because of "social" reasons (like reduced opposition to C&R, location, etc.).

 

[Chaz]

Based on what certain individuals from PFBC have said, they don't think that brook trout fishing will improve in those streams, so they are already biased. They've also said that if more angler use isn't evident they'll consider the program a failure. Not exactly open minded Jack, is it?
OH. I can name at least 10 streams that I know where the brookies are carnivorous and grow large even by brown trout standards. These streams forage base consists of mostly other fish and not much else. I know 3 Pocono streams that have very good populations of both forage and other fish where the brookies grow fairly large. It is not limited to limestone streams, in fact only 2 of the streams I have in mind are limestone streams.

 

[JackM]

I have never accused you of being open-minded, Chaz.

 

[troutbert]

JackM wrote:
Before we know the results, will anyone go out on a limb and say whether they think the program will provide data that is valid from a scientific standpoint? I will abide by the objective findings-- will the rest of you?

Objective? We would need some objective parties to determine whether such studies would be objective or not. I can't think of any off hand.

 

[OhioOutdoorsman]

Chaz, you're probably right and my professor friend is wrong (seriouisly). My experience as a spin fisherman years ago before I became a fly fisherman taught me that nothing quite liked a panther martin spinner like a brook trout...4" brookies would hammer 2" brook trout colored spinners. When I fish for brookies these days, I'm a dry fly snob, but maybe I'll start throwing more streamers.

 

[FarmerDave]

JackM wrote:
Before we know the results, will anyone go out on a limb and say whether they think the program will provide data that is valid from a scientific standpoint? I will abide by the objective findings-- will the rest of you?

That depends on a few things, Jack. If the study is not independent, and it's intent is to prove an pre-conceived notion, then no.

This has been the case with all the studies so far that I have seen. They may suggest one theory or another, but if it suggests something other than the preconceived notion, it will be declared inconclusive and we will go back to the status quo. That is the problem with studies that have so many variables, and are not independent.

In simpler terms, the result will more than likely be either they were correct, or they were not incorrect. That my friend is not scientific.

Correction (added): I'll go out on the limb and agree that the data will be valid, but I won't agree that the study and the conclusion will necessarily be un-biased until I know the details.

 

[FarmerDave]

Ohio, Chaz is definitely correct on this. All trout (and char) will eat other trout (and char) if they can get them in their mouth, and they don't check for spots first.

 

[OhioOutdoorsman]

Well,

Here's how I would interpret the results:

On a stream by stream basis, if either the biomass was improved or the bimass was the same and the average fish became larger, I would say it was a success, and lets keep the C and R regs.

If the biomass did not change and the average fish was smaller or the biomass was reduced, i'd say it was a failure, and lets go back to the standard regs.

Again, this would be on a stream by stream basis.

I'd agree to abide by these results/conclusions.

 

[OhioOutdoorsman]

Well, if brook trout are cannibals (and self-cull) or if spawning habitat or trout habitat is a bigger limiting factor than nutrition, then, I agree, any sort of culling by humans will not help improve fish size.

How about rainbows, my professor friend says they need to get to 18-20" before they start eating signifigant numbers of fish.....do you guys think they are different?

We can all agree browns are carnivores.

 

[shipnfish2006]

OhioOutdoorsman wrote:

How about rainbows, my professor friend says they need to get to 18-20" before they start eating signifigant numbers of fish.....do you guys think they are different?

We can all agree browns are carnivores.

Well considering I've caught wild rainbows as small as 9" on streamers I'd say as soon as they can catch baitfish they'll eat them. Then in order to eat a "significant" amount they obviously need to be a little bigger. So I can see where saying 18-20" to eat a significant amount to actually affect anything because if the forage is there the smaller ones will be able to expend less energy picking off the other things in the stream rather then chase other fish all day.

 

[troutbert]

Trout populations swing wildly up and down on freestone streams, even with C&R, such as on Slate Run, because droughts, floods, winter kill, variation in spawning success etc. For this reason it is very difficult, perhaps impossible, to conduct studies that are really quantifiable.

How can you conduct the effects of varying regulations against a backdrop of a population that swings wildly because of natural factors? The answer is that you can't.

Does this mean that harvest and regulations have no effects on populations? Of course not. That just doesn't follow logically. It only means that it is difficult to design a test that determines the effects.

 

[JackM]

So for all who won't embrace the validity of the experiment ahead of time, please spare us the "I-told-you-so" if the results end up supporting your own theory of the positive effects of C & R.