Question regarding Wild Brook Trout Enhancement Program

[k-bob]

from maine's brook trout management plan, 2009, ez to find online:

"Brook trout are capable of extremely diverse growth rates, which are primarily dependent on such environmental factors as basic productivity, water temperature, and food abundance. A 5-year-old brook trout may weigh less than 2 ounces in waters with poor growth conditions. At the other extreme, a trout of the same age may weigh 4 or 5 pounds if growth conditions are ideal. Brook trout are generally shortlived, with relatively few survivors beyond 3 years of age. A few individuals may attain ages of 4 to 6 years, but rarely more."

a 5 year old ST might weigh 2 oz or 72oz! a bit later...

"recent studies indicate that Maine’s wild brook trout populations
have not been genetically compromised due to excessive harvest of the older, mature fish."

if brookie dna has not been damaged by selective harvest of mature fish in maine, where some ST are in lakes, so they live longer and get bigger, I am not sure that it has been in little PA headwater streams...

there's also the michigan info on the potential impact of higher harvest regs in small stream ST. no mention of the idea that higher harvest of relatively big ST would degrade DNA, making future ST smaller...

 

[Chaz]

k-bob wrote:
from maine's brook trout management plan, 2009, ez to find online:

"Brook trout are capable of extremely diverse growth rates, which are primarily dependent on such environmental factors as basic productivity, water temperature, and food abundance. A 5-year-old brook trout may weigh less than 2 ounces in waters with poor growth conditions. At the other extreme, a trout of the same age may weigh 4 or 5 pounds if growth conditions are ideal. Brook trout are generally shortlived, with relatively few survivors beyond 3 years of age. A few individuals may attain ages of 4 to 6 years, but rarely more."

a 5 year old ST might weigh 2 oz or 72oz! a bit later...

"recent studies indicate that Maine’s wild brook trout populations
have not been genetically compromised due to excessive harvest of the older, mature fish."

if brookie dna has not been damaged by selective harvest of mature fish in maine, where some ST are in lakes, so they live longer and get bigger, I am not sure that it has been in little PA headwater streams...

there's also the michigan info on the potential impact of higher harvest regs in small stream ST. no mention of the idea that higher harvest of relatively big ST would degrade DNA, making future ST smaller...

Fishing pressure is much lighter in Maine than it is in PA. Maine has been at the forefront of conservation of brook trout PA has not. But you can see what the biologists in Maine are saying, they are saying that the range of size and weight of brook trout varies widely, all I'm saying is that the fast growing big fish exit only in places where they haven't been over exploited.

If we can get past the over exploitation of brook trout, and add to that, the fact that brookies are limited because of habitat that is not dominated by brown trout or rainbow trout, then we can see that the expectation that we can grow brookies that are larger is very limited by these 2 factors. The problem is that in 99% of brookie only streams the fish are small,

 

[k-bob]

chazster: "The problem is that in 99% of brookie only streams the fish are small,

 

[afishinado]

k-bob wrote:
chazster: "The problem is that in 99% of brookie only streams the fish are small,

 

[k-bob]

thanks afish, and everyone this thread really got me reading stuff.

 

[tyeager]

I understand all the scientific literature, and I understand that there are many factors that can lead a study to be intrinsically accurate or extrinsically accurate. Both types of studies are valid and will likely produce different results. I have not read any of the above literature so take the following as you may.

When I fish small ST streams I do not fish them to catch the average fish. I believe for the most part PA is past having large average size brook trout without a complete over haul of regulations and philosophies of all fisherman and government agencies involved. So when the scientific studies argue that average size is not increased I couldn't care less.

I'm looking for the outlier fish. That is older and is larger (whether due just to age, later sexual maturity, or genetics). I don't care if only 30% of brook trout survive, I believe larger trout in prime lies in better than average holding water have a higher chance of survival than the average fish. So the survival rate argument to me is moot.

If catch and release were a regulation on more brook trout waters then more brook trout would survive. This may not be a statistically significant number of brook trout but it may be a number that anglers notice. Especially since the harvest is of individuals that are considered above average size for brookies in general.

Opponents will say that the studies show that the rate of survival is statistically insignificant and I can't argue that in those studies this is true. But, in a stream that provides quality fishing for a quarter mile of its length that has say 65 brookies over 6" in this quarter mile and 10 over 9" then losing 5 of the larger fish to harvest in my opinion will hurt the fishery in the eyes of the angler.

 

[Chaz]

The cropping was done over a very long period, and I never called it cropping, because I don't think it's really happening in the present to be called cropping it would have to be happening in the present, in my mind. Those genes for large slow growing brook trout are gone from the gene pool. What has survived are the early maturity genes and genes for slow growth. The habitat that is left for brookies is generally poor, but where you find good habitat is where you find more diverse populations of brook trout. The diversity is what makes a strong population of fish, not the quantity of fish.
:edit
I will add that regulations are only 1 technique for increasing the size of brook trout, and have to be part of the management plan. The question is, what should those regulations be?

 

[Chaz]

tyeager wrote:
I understand all the scientific literature, and I understand that there are many factors that can lead a study to be intrinsically accurate or extrinsically accurate. Both types of studies are valid and will likely produce different results. I have not read any of the above literature so take the following as you may.

When I fish small ST streams I do not fish them to catch the average fish. I believe for the most part PA is past having large average size brook trout without a complete over haul of regulations and philosophies of all fisherman and government agencies involved. So when the scientific studies argue that average size is not increased I couldn't care less.

I'm looking for the outlier fish. That is older and is larger (whether due just to age, later sexual maturity, or genetics). I don't care if only 30% of brook trout survive, I believe larger trout in prime lies in better than average holding water have a higher chance of survival than the average fish. So the survival rate argument to me is moot.

If catch and release were a regulation on more brook trout waters then more brook trout would survive. This may not be a statistically significant number of brook trout but it may be a number that anglers notice. Especially since the harvest is of trough that considered above average size for brookies in general.

Opponents will say that the studies show that the rate of survival is statistically insignificant and I can't argue that in those studies this is true. But, in a stream that provides quality fishing for a quarter mile of its length that has say 65 brookies over 6" in this quarter mile and 10 over 9" then losing 5 of the larger fish to harvest in my opinion will hurt the fishery in the eyes of the angler.

Well said.

 

[k-bob]

"I'm looking for the outlier fish. That is older and is larger (whether due just to age, later sexual maturity, or genetics). I don't care if only 30% of brook trout survive, I believe larger trout in prime lies in better than average holding water have a higher chance of survival than the average fish. So the survival rate argument to me is moot.

If catch and release were a regulation on more brook trout waters then more brook trout would survive. This may not be a statistically significant number of brook trout but it may be a number that anglers notice. Especially since the harvest is of individuals that are considered above average size for brookies in general."

Anyone know if natural mortality is lower for bigger fish, which may for example be in bigger holes? maybe less prone to predators or floods, but disease?

probably depends on level of fishing pressure and harvest. wbtep study suggests cropping wasn't happening, not that it couldn't happen.

 

[Chaz]

If we take the 70% annual mortality at face value, it means 70% of the population(all trout). I would think it's most likely higher for each year the fish lives. In other words as a year class ages it loses a higher percentage of individuals

When we look at PFBC studies, we see many times that YOY class has the largest number of individuals. as each survey is completed each year class diminishes in individuals. On our trout streams the oldest fish are the least number of individuals.

Now the one wild card is of course years where you lose 90% of the population due to some weather event, or when you lose an entire year class of fish. I believe this happens more often than we realize, but nature has ways of dealing with this, as long as the event doesn't wipe out an entire population, productivity will increase in subsequent years after such events until the population reaches some arbitrary balance.

This balance is something that is unknown in most populations. I believe it is important to know only then can we really manage trout populations to get the returns we want. We can only improve populations when we manage habitat and have special regulations as tools to manage with. That doesn't mean special regs everywhere. It means special regs. where they are needed to achieve a certain goal.
I believe the biggest factor to attaining larger trout in nearly all of our streams is there are not enough pools and structure. It doesn't matter where I fish, I always find the bigger fish where there is big fish habitat.

 

[JackM]

I haven't read the last two posts, but this struck me as ridiculous, as much as I am able to agree with Chaz occasionally:

"Those genes for large slow growing brook trout are gone from the gene pool."

 

[JackM]

In other words, human beings are more likely to breed out characteristics that make it unable to adapt to present conditions, even if they are suddenly changed or changing. Brood characteristics are widely diverse in brood animals. But we have had this discussion before.

 

[Eccles]

Perhaps it might be useful to simply look at this in terms of selection pressure and not get mixed up with genes and DNA and all that stuff.

Trout live in habitats that range from being very suitable - lots of food, nice water temps and flows, plenty of refuges etc - to being very harsh.

The population in the suitable, stable habitats (limestone creeks, larger freestones etc) are shaped more by density dependent effects (competition between individual trout for space, feeding lanes, mates etc) and disease and predation. These factors shape the population size, age and size structure. Healthy populations in these waters have good age class representation and of course a few large ones that disproportionately contribute to subsequent generations. We can act as a strong agent of selection on these populations (an uber predator) by selectively harvesting the largest most fecund individuals over time. This pressure favors (selects for) those few individuals that mature early at a small size, those that were once rare in the population but now in the absence of the big ones come to represent the majority in the face of our over-harvest - it is their also small also early maturing offspring that will now make up the population. This has been shown to be a major driver in the collapse of commercial marine species like cod, has been shown to occur experimentally in freshwater fish and demonstrated that it could occur from recreational over-harvest. Though I am not aware that there has been any documented occurrence in a natural populations subject to historical recreational angling it is generally agreed that if the selection is high enough such a sequence is likely.

At the other end of the scale are those populations at the range edge, enduring the harsher conditions in headwaters and other marginal, unstable habitats. There may be some density dependent effects but the overwhelming driver shaping the population is the abiotic environment - drought, floods, high water temps, anchor ice etc - and lack of food. Predation and other biotic factors barely feature as selection agents because the harsh conditions and low food supply take care of most of the fish (that annual 70% annual mortality rate for e.g.).

My understanding of the WBTE creeks is that they were much more likely to be headwater streams and so the major selection pressure acting on the trout would be coping with the weather and poor food supply. The best way to deal with this (if you don't migrate out) is to make sure you mature and spawn early before you die in your third or fourth year. Since the food is a bit iffy and temperatures rarely ideal you'll also likely do this at a pretty small size. It may look the same as selection by recreational fishing harvest but the driver of selection is not the angler but the indifferent environment.

I don't know if this will help clarify the topic for anyone.

And apologies for the length of the post.

 

[Chaz]

Of the streams in the program that I've fished and others described to me, only one has an excellent food base, the headwaters of Kettle Creek. In Kettle Creek there seems to be plenty of 8 and 9 inch brookies, but very few if any larger. I've fished this section many times, and it's hard to find any larger.

 

[k-bob]

Thanks Eccles! Your comments fit Behnke's discussion in About Trout (122). He notes that genetic-based growth changes may occur with highly intensive, size-selective commercial pacific salmon fishing, where fish are removed before they have a chance to spawn. Commercial fishing, similar to the cod you mention.

But Behnke also states that "there is no real evidence that a wild trout population in any stream has ever experienced a genetic-based growth change due to angling" (top p 122). This fits with your statement that you aren't familiar with cases in which recreational angling led to genetic-driven growth changes.

I appreciate your ideas on how short lifespans due to the high levels of environment-driven mortality in infertile headwaters trout streams could lead to hereditary pulls toward early maturity at smaller sizes. thanks!

 

[KenU]

According to old angling literature, brook trout in Kettle Creek, Loyalsock and probably all the larger freestone streams, moved with the seasons, because the bigger waters became too warm in the summer. They wintered over in pools in the larger downstream waters, then spent the early spring months feeding up on larger prey (minnows, crayfish, etc,). [Trout must switch over to larger prey once they reach about ten inches if they are to continue to grow.] As the summer sun warmed the big downstream waters they moved upstream into headwaters and tributaries where they spent the summer months. And you can bet they fed heavily on the little brookies living in these smaller waters. The parmachini belle, which imitated a small brook trout, was a popular fly in the 'good -old-days.' After spawning in the fall they moved back downstream into the larger waters and began the cycle again.

These movements typically occurred during high water events.
This was the life history that allowed brook trout to grow faster and larger than small-stream-resident brookies. Now, we stock and plunder these larger downstream waters every spring - the very time during which brookies grow at a maximum rate. Brook trout still can and do utilize large reservoirs, lakes and even the ocean to maximize growth and therefore size. All this has been lost or forgotten in PA.

By the way, these movements still occur to some extent. I have seen them myself and they are awe inspiring. Brookies on the move will sometimes gather in large schools in pools at the mouths of tributaries. Then, in a few hours, they are gone...upstream to cooler water.

 

[k-bob]

OK, but Behnke's About Trout, which reprints articles from this noted trout biologist, is quite clear that: 1) the genetic influence of bigger trout is not removed from the gene pool if such fish are harvested by anglers. These larger fish will already have spawned, and the larger females lay more eggs and the larger males may spawn with larger females. 2) Growth related genetic issues may result from intensive size-selective commercial fishing, but he sees no evidence that they have ever resulted in stream trout from angling.

Behnke clearly states that with rare exceptions such as commercial steelheading and some bizzare trout that first spawns at 10 lbs., he sees no genetic justification for special regs (121-122).

 

[Chaz]

One fall on Fishing creek I saw one of those brookie migrations, thousand of brookies moving upstream for a spawning run in mid-Oct. couldn't catch any, but they were all in the 8 to 10 inch range, nothing larger.

 

[afishinado]

Chaz wrote:
Limestone streams have the ability to produce brookies that would rival the browns in size, if the browns didn't push them out. If you were to ask me the 2 species in the same watershed are incompatible.

Afishinado wrote:
Big Spring is about as fertile as any stream anywhere. Brook trout grow to about 15-16" maybe, but has anyone caught any approaching 20" or even greater there? If so, they are extremely rare.

A brown in the 18-20" gets a "nice fish" nod, but is hardly a head turner.

^ No one answered this question.

Big browns and rainbows regularly grow to 20+++ inches in Big Spring. Not brookies. Why not in such a fertile stream?

All signs point to genetics. Has it always been that way, or has the genetic make-up of these fish been altered. Do brook trout max out in size at the mid teens in length in PA and has it always been that way? My guess is yes.

 

[troutbert]

There are many historical references of 20 inch brookies in PA, MD, WV. And these were in freestone streams.

How big they got in limestoners like the Letort or Big Spring or Little Juniata, nobody knows.

The limestone valleys were settled much earlier than the big freestone drainages.

I've never seen any record of how big the trout were in those limestone streams when the first settlers arrived. I think those early settlers just caught the fish and ate them, and never thought it was something worth writing about. It wasn't sport fishing, it was just putting food on the table.

But if brookies reached 20 inches in the freestone drainages, it's likely they got bigger than that in the limestoners.