Catch and Release Mortality

[Nighthawk]

I think a lot of the bass morality is because they are not released immediately but after several house of riding around in a live well of a boat, weighed, put in a holding tank and then release. There has been a lot of study on bass and the effects of tournament fishing on them. I think that is where a lot of the data on bass comes is obtained. Fishing farm ponds in Mississippi I have caught the same bass several times.

Here is an article from paflyfish discussing the effect on the two warm water rivers in my county.

http://www.paflyfish.com/smartsectio...a-rivers..html

These rivers are now strictly catch and release for bass. Thing is for decades the rivers have been catch and release only for any bass under 15 inches so what has caused the population crash especially in the once world class small mouth fishery of the Susquehanna river? I think the PFBC is on the right track when they talk about reduced levels of dissolved oxygen caused by agricultural run off. The same thing affects our trout streams of course. That has to make it hard to nail down exact numbers on catch and release mortality rates.

Environmental conditions in the individual fishery has a large impact on C&R rates in that fishery.

[Silver Creek]

Silver,

The numbers of large trout will always decrease fastest, regardless of the reason for any mortality. Even if the cause of death is spread evenly across all age ranges, the larger fish will show more decline simply because to become a larger fish, you have to be a smaller one first.

Buddy

Hi Buddy,

I understand that there are fewer large fish than smaller fish from natural mortality as they grow.

What I am addressing is something different. I am asking whether all age and size classes of fish show the same percentage decrease with C & R. If the larger fish with C & R are disappearing from the river at a higher rate than smaller fish, I am asking why. I am asking whether all the size classes of fish show the same decrease.

The study is incomplete if it says that the larger fish are disappearing, but does not say why. They assume it is C & R alone and I think it could be poaching. I am saying it cannot be C & R alone UNLESS they absolutely rule out poaching. It seems to me that the larger fish are harder to catch, so they should be caught less often that smaller fish - ie, they should be caught less often per year than a smaller fish. Hence I think they should have a higher and not a lower rate of survival.

Perhaps I am not getting why a larger fish being a smaller fish first means than a fish that grows to be large should die at a faster rate due to C&R. Have they not proved by surviving to be larger fifsh that they are genetically superior to the average smaller fish? So they should be more robust adn not less.

[spinner1]

my log books tell me that in the 34 years I have kept logs....
I caught about 1,200 trout when I began my logs and last year about 2,200
Population density has caused some of the fewer big trout.
More trout...less food......slower growth rate....

[spinner1]

there have been studies done here also by the WDNR
and the types of anglers have changed in Wisconsin
.
The worm and spin anglers for trout have decreased
dramatically. The meat eater out here are way down.
They prefer fishing for crappies and something that
they can keep more of.

Wisconsin has manged themselves for more trout and a
byproduct of that is a change in size.

[Buddy Sanders]

Silver,

We are probably thinking the same things but writing them diferently. My main point was that populations are not static. When they 'count' fish, they don't and can't count them all.

WE need to keep a close eye on such 'studies' as their political intent is often unclear until just before they try to change our regulations based on them. By the time it gets to that point, the acuracy of the data collection and the other 'factors' that we can easily see effecting the numbers can be lost in the political retoric to 'do something'.

There is a movement out there to eliminate catch and release completely. It's happened in some areas overseas already. It's the first logical step in getting us to stop fishing entirely. What many of us saw as a ethical way to help manage the resource is being turned against us. Doing studies that bring the practice into question always make me nervous.

Buddy

[flyguy66]

We really have 2 choices when it comes to this topic: C&R or no R, just C. Fishing isn't going to stop. We're certainly not going to advocate it! The issue becomes, then, that fishing with the R = 100% mortality and C&R reduces mortality. The fisheries managers need to figure out how much to the best of their ability, but it really doesn't matter much to laymen. All that matters is whether or not we should support/practice good C&R whenever we don't want to keep fish within legal limits for consumption. There's nothing wrong with a certain amount of that, either. The professionals set limits on that based on sustainability studies as well. If the agencies in your state are allowing politics to guide their decisions instead of science, then you need to address that problem. But the constant questioning of "to C&R or not to C&R" is pretty silly. It's a well-settled debate with plenty of science to prove that C&R (even when poorly executed) does...in fact...reduce mortality vs. catch and keep.

Next, we must realize that nothing goes to waste in nature. A dead fish is consumed entirely by the riparian zone in which it lived. That is why the salmon that die after a spawning run are so important to revitalizing the watersheds they run up. When spawning runs stop for whatever reason, there is a cascading effect that has been traced to the loss of the dead salmon carcasses upstream. Circle of life stuff, gang. We're a part of nature, not just an outsider that has a purely negative impact on it. If we reduce the mortality of our fishing by 95 to 85%, we've done a very good thing.

It is true that most fishing mortality studies have to be crafted to study it in a well-defined set of circumstances. Otherwise, the studies would not be scientific. Studies in "natural conditions" are not scientific by definition. There are too many variables and no ability to establish a double blind set of controls. It is also true that almost all of the bass mortality studies are done in the context of tournament fishing because they can collect a very discreet set of data in a short period of time. Thus, the studies are cost effective. Well, you don't need to be a rocket scientist to figure out that if someone stuck a crankbait in your gullet and ripped you out of the lake on 40 lb test, flopped you into a hard boat, yanked the bait out of your mouth really fast, tossed you into a live well, left you there all day, then dumped you in a plastic bag and carried you to a stage, weighed you, and then awhile later someone finally dumped you back into the lake into a holding pen where you were to stay for a day or 2 with a bunch of other shocked and dying fish, you'd want to die too! Mortality from these studies runs in the range of 30 to 75%...depending on the exact format of the study. One of the best constructed was done by TPWD on Lake Fork a few years ago. They carefully worked to minimize stressors and spent a lot of extra money to remove artificial stressors from the experimental environment. The mortality rate was about 30%...which is fairly consistent with what had been previously postulated about the baseline mortality rate for C&R fishing with multi-hook lures and baits that fish inhale deeply.

[Silver Creek]

my log books tell me that in the 34 years I have kept logs....
I caught about 1,200 trout when I began my logs and last year about 2,200
Population density has caused some of the fewer big trout.
More trout...less food......slower growth rate....

Hi Spinner,

I can see how more trout = fewer big trout. However, that begs the following question. If that is true, why do the old timers tell us that there were more and bigger fish in years past. What I am saying is that left alone, the trout population will reach a steady state with a relatively stable population distribution of smaller to larger trout when rainfall and other external factors stay normal.

What I don't understand is how C&R can change the steady state population distribution of smaller to larger trout (more small trout and fewer larger trout). If the fish are caught in the same proportion and have the same C & R mortality, the relative population distribution should not change; ie., there should not be more smaller and fewer big trout. Again, if this happening, I suspect poaching.

Anyone who has fished the C & R "special regulation" areas in Wisconsin has seen worm containers where there should be no bait containers. I believe the results are skewed because regulations do not prevent fish harvesting. Enforcement does and it is pretty thin where I fish.​

[spinner1]

Hi Spinner,

If that is true, why do the old timers tell us that there were more and bigger fish in years past.​

Many of those big trout caught in the old days were released brooders or hatchery fish.

My friend Matt Mitro at WDNR tells me wild trout are smaller and we should get use to the idea of generally smaller trout.

I would really be curious to find out what Matt thinks about your question:

Matthew G. Mitro, Ph.D. Coldwater Fisheries Research Scientist Wisconsin Department of Natural Resources, Science Services Science Operations Center, 2801 Progress Road Madison, Wisconsin 53716 608 221 6366 phone 608 221 6353 fax matthew.mitro@wisconsin.gov

Len

[Bear742]

I am enjoying the responses to the summary I posted. Considering that the article is about Brook trout, I would not try to use it to draw conclusions on Bass though I would like some references to studies on C&R Bass mortality. I keep in mind that tournament mortality is a special issue. Since I release bass immediately, they are not subject to the stress of livewell and weigh-in. Most C&R Bass are not.

My post was a summary. Did anyone look at the original? Also:

The author draws information from this article, Risley, C.A.L., and J. Zydlewski. 2010. "Assessing the effects of catch-and-release regulations on a brook trout population using an age-structured model." North American Journal of Fisheries Management 30:1434-1444

That would be the place to look for details on the effects of factors like age. I am not even sure if I could get a copy of the study. I might try.

[Panman]

Westfly has had some interesting discussions on this subject. One item that got my attention was the increased mortality of fish that had been removed from the water for whatever reason and then returned. Here is a quote from that study.


Exposure to air and mortality rate:
“Ferguson and Tufts (1993) reported disturbingly higher mortality among domestic
rainbow trout subjected to air exposure after mimicked angling events than for control
fish or experimental fish not exposed to air. Their data revealed 100% survival among
control fish and 88% survival among exercised (i.e., “angled”) fish. Among fish that were
exercised and then exposed to air for 30 and 60 seconds immediately thereafter,
survival dropped to 62% and 28% respectively. The authors stressed their results had
important implications for Atlantic salmon sport fisheries where the marked trend was
toward catch and release but where anglers habitually hold fish out of water for
significant periods of time prior to release"

Tim