Catch and Release Mortality

FAOL Community Fly Anglers Online
1

Since the original discussion on the reader’s voice forum in November, I came across an interesting report on Catch and Release mortality.

Believing firmly that Murphy was an optimist, I have always had the nagging belief that not all live released fish survive. However, putting a number on the mortality rate has always been the problem. Obviously I was happy to see a research based article on the subject.The whole article was in North American Fisherman. Unfortunately I could not find a way to link to it. Here are some highlights from the article.

RESEARCH UPDATE
“Handle With Care”, by Dr. Hal Schramm, North American Fisherman, Dec-Jan 2012 p.16

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

"Memories and embellishments aside, I think there is good biological evidence to support the contention that, indeed, some fishing isn’t as good as it used to be. Let me share an example for brook trout fisheries based on some population modeling done by Maine fisheries scientists.

"Good brook trout fisheries," those with numbers of fish larger than 12 inches contain a lot of old fish. Brook trout typically reach almost 8 inches by age 2, 10 inches by age 3, 11 inches by age 4, and surpass 12 inches by age 5. To get old, fish have to escape capture or survive after release.

"There is always some level of mortality, even when fish are handled gently and kept in the water for unhooking. Actual measured rates of post-release mortality for brook trout caught on single-hook flies are 0 to 14 percent, and average about 5 percent. It is considerably higher for actively fished lures, and jumps to about a 32-percent average for passively fished bait.

"As you might expect, the number of larger and older fish declines as hooking mortality increases. When hooking mortality increased from 0 to 14 percent (the range for single-hook flies), the calculated numbers of age 4 and 5 trout declined about 28 percent at low levels of fishing effort.

"Increasing the fishing effort had an even greater effect. With a 5 percent mortality rate, a fishing effort of 400 angler hours per acre per year cut the number of age 4 and 5 brookies in half, compared to no fishing effort and only natural mortality.

"While 400 angler hours per acre may seem high, it really isn’t. An acre of brook trout stream may be one-half mile long. And the 400 hours can be reached by only two anglers fishing four hours each per week in the half-mile reach. This and higher levels of fishing effort have been measured in many Eastern brook trout fisheries.

"Brook trout are extremely resilient; and, as the population is reduced, the remaining fish will spawn at younger ages and the offspring will have higher survival rates. Thus, catch rate will tend to remain high, but the fish will be small."

This brings some true light into a discussion which is too often dominated by smoke and wind. I hope you enjoyed it.

2

I have used the 5% figure (the average for single hook fly) wen I do presentations for several years. Thanks for the reference and further explanation of the statistics. Of course, all bets are off when fish are handled roughly or pressure exceeds the capacity of the water. Thanks!

3

In the back of my mind I’ve wondered how many of the fish I let go survive and how catch and release mortality affects fish populations. Worries that i was killing too many bluegill I caught on bait caused me to give up the pratice except when I am going to keep them.
I read an article in a musky fishing magazine that essentially said that muskies deeply hooked on live bait were going to die because of tears in the stomach or esophagus, I’ve forgotten which, so it doesn’t matter whether you cut the line or remove the hook.

4

I like to fish the rivers of Montana and eastern Washington. I hook a lot of fish and release all of them. Many of the trout show the scars of many previous hookings around their mouths. That to me shows that Catch and Release really works. Also, it is rare to observe dead fish on the bottom of the rivers as we drift over the water. When fish die they usually don’t just float downstream, they sink to the bottom and the water really doesn’t move them very much. It is easy to see the salmon that have spawned and died and every now and then I see another species of fish, often Northern Pike Minnow, dead along the bottom, but rarely do you see trout. When you consider how many fishermen fish a river like the Missouri River in the Craig to Cascade stretch, if there was a high rate of fatalities from fly fishing then you would see the bottom littered with dead fish, but you don’t see that.

If the fish is brought in quickly and handled properly that fish will live to catch another fly another day.

Larry —sagefisher—

5

There is nothing in the report that states how hooking mortality is age or size related; or how hooking rates differ for age or size. Without that data, one must assume that hooking rates and mortality rates are identical regardless of age or size. If that be so; since there are much fewer large trout than small trout, many more small trout die. Similarly, if there are few large trout, a given death of a large trout has a greater effect on the number of larger trout.

I’d like to know what the gross number are. For example, if a mile of stream has 1000 "large trout and population crashes 50% we still have 500 large trout and the average fisher will likely have a shot at a large trout. If the number is 10, and it goes to 5; even before the crash, it is unlikely for a fisher to catch one of those 10 large trout.

The study also assumes that there is no poaching of the larger trout to account for this decrease. Knowing what happens in my native Wisconsin, that is not true. I suspect that the decrease in larger fish is due to poaching. So again we need to know the gross numbers. If the population of large trout is going down faster than the rest of the population, how can we explain that? Poaching and illegal harvest would be #1, 2, 3 and 4 on my list. If that be so, the problem is not C&R, it is illegal harvest.

6

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.

We all know that some fish die as a result of catch and release. The real question is whether or not catch and release is a sustainable practice, or if limited catch and kill would better benefit the populations. There is division here, simply because anglers have grown more skilled, and catch rates can reach the level where a 5% mortality rate would exceed a daily creel limit.

So, would it be better to require anglers to kill and keep the first two or three fish they catch, then stop fishing, or allow them to catch and release all the fish they want?

In areas of high angler pressure, I beleive that catch and release is the only viable option, but there is debate about it. It really dosn’t matter on areas of low angler pressure.

Poaching, on the other hand, is something we’ll have to live with unless anglers are willing to get involved with enforcement. Budget constraints at every level of of public service are shrinking the ranks of our wildlife regulations enforcement personnel. You seldom see an officer on lakes or streams anymore.

Buddy

7

Buddy:
You raise two interesting points; limiting ourselves to a reasonable number of fish a day and actively participating in reporting violators. I’m a Leave No Trace educator and at one extreme LNT may be interpreted to discourage all hunting and fishing. However,since it is a program of principals and not rules, a reasonable accommodation would be to limit ourselves to a set number of fish (suitable to species and environment) regardless if we catch and release or not. In this case we would stop fishing when we have caught what we might think a creel limit would be. I think this would be an ethical solution and I am going to practice it in the future and suggest it in my presentations.

We have a TIP (Turn In a Poacher) program here in Indiana. I’m sure it is in other states and countries too. To me, it is a responsibility to turn in a poacher. It is unethical to not turn in a poacher.

Thanks for the suggestion.

8

All good points. I am never sure how these studies are constructed when we are given a synopsis of their findings.

Catch and release is far from perfect but catch and kill is 100% mortality. I think how a fish is caught and released is very important. How about barbed versus barbless hooks. I have fished the Montana waters with guides who all use barbed hooks. Sometimes they play hell with getting the hook out and I wonder if the fish ever makes it. I have also seen little effort expended to revive the fish, just get the hook out and dump it back in. Likewise, catching and playing a fish either just for the fun of it or by using tackle that is too light has got to wear the fish out – only to be followed by unhooking and releasing the fish (either from a net or by releasing without taking it out of the water) without any revival time. What about keeping the fish too long while taking a picture?

How about our ocean waters for Salmon? They often have a size limit and you sure don’t know what size you have on until after you have landed the fish – especially if it is close. Those fish probably get dumped back into the water with little chance of survival. Perhaps having to take the first fish you catch is the way to go, regardless of size (but then you have the upgrading problem).

Interesting topic.

9

… I’ve read suggest that different species sustain significantly different fishing mortality rates. My recollection is that bass typically sustain a high mortality rate, and that trout sustain a much lower one. Bait fishing generally produces higher fishing mortality, regarless of species, than fly fishing.

Speaking of trout only, and fly fishing only, it is likely that fishing mortality rates will vary among populations of trout, or other fishies, based on the quality of their habitats, all other things being equal.

I suspect that some of the study results also include stocked trout populations, and that alone would most likely affect the outcome, compared to studies of wild populations in favorable natural habitats.

My own experience is almost exclusively with wild trout, and, in good part, with wild native trout in very favorable habitats. The figure often cited for fishing mortality for trout - 5% plus or minus - always seems very high to me based on my experience. From the very low number of trout I see bleeding at all, and the vigor which most of them exhibit after release, suggests to me that given quickly landing them and employing reasonably good C & R methods, that the mortality is probably down in the 1-2% range, if that high.

I did have occasion this summer to fish for some smaller stocked rainbow trout in an Idaho “put and take” fishery. Those were the most pathetic little fishies I’ve ever seen. I fished there twice, got bored and got sad, and gave that up for good.

For those who haven’t seen it, the linked thread might be of interest, or at least enjoyable. It features one wild native Westslope Cutthroat that I caught four times over a period of almost four months, another one that I caught six times in a matter of weeks, and a number of other fishies caught multiple times.

http://www.flyanglersonline.com/bb/showthread.php?43168-Same-fishies-!!

One point made in the linked thread, is that wild trout, and especially large wild trout, are a lot tougher than most people give them credit for. That cutt with several osprey talon marks in his back had it worse the day he almost got ate than the two times that I caught and released him. :shock:

John

10

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.

11

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

http://www.paflyfish.com/smartsection.item.178/long-overdue-catch-and-release-will-now-be-required-for-some-sections-of-the-juniata-and-susquehanna-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.

12

[SIZE=3]

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.

[/SIZE]

13

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…

14

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.

15

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

16

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! :wink: 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.

17

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.​

18

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.

[b]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[/b]

19

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:

[i]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

[/i]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.

20

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