The MDC smallmouth study

[Al Agnew]

Last month the Smallmouth Alliance had MDC people in to discuss their findings in their latest study. I've since been able to read and consider it in depth. I thought a more detailed report on it with my thoughts might be of interest to those on here.

The study is entitled "Harvest Evaluation of Smallmouth Bass from Selected Ozark Streams". Six different stream sections were studied. They included: Black River from the confluence of the West and Middle forks to Hwy. K, Castor River from Hwy. 72 to Hwy. 34, Courtois Creek from Hwy. 8 to the Huzzah, Current River from Van Buren to Cataract Landing, Current River from Two Rivers to Roberts Field, and North Fork from Osborn Crossing to Rainbow Spring. I have been on all these streams in recent years, and am quite familiar with all of them except the North Fork. While the reaches sampled give a good cross section of different size waters from wading streams to jetboatable rivers, they are all characterized by clear to very clear water and are probably less fertile than some other Ozark streams.

The study captured, tagged, measured, and took scale samples for aging from anywhere from 169 to over 400 smallmouth over 12 inches on each section in both 2011 and 2013. Intent was to tag the fish before the season opened both years, but in a couple of sections tagging wasn't completed until after the season opened. The majority of the tags had rewards of $25 for reporting them, with a lesser number having rewards of $75. The main goal was to see how many tags were returned and how many anglers returning tags reported that they harvested the fish, within a year after tagging, and how quickly the fish were caught after tagging.

Some estimates and assumptions had to be made, such as how many tags were lost from the fish during the time period studied, how many fish were caught and not reported (the rewards should have minimized that figure), and what the annual natural mortality was--how many fish died of natural causes before being caught. They did a controlled study of tag loss which showed it to be small. They figured something like an 85-90% reporting rate. And then there was the mortality thing. Overall, they assumed that around 30% of the fish tagged would die of natural causes during the year, but this figure changed from one section to another, and I wasn't able to figure out exactly how they arrived at those figures.

So they knew how many they tagged. They knew how many were reported as being caught. They knew how many were reported as being harvested. They guessed at how many died of natural causes.

Some figures--first number is the 2011 results, second number the 2013 results:

Tagged fish caught and reported:

Black River--54-45%

Castor River--46-64%

Courtois Creek--52-47%

Current River, Big Spring area--56-57%

Current River, Powdermill area--59-56%

North Fork--51-37%

This shows a LOT of the smallies in these streams are being caught! Keep in mind that this was just what was caught within a year after tagging. In fact, the median days the fish swam around without before being caught was 22-47 days, and depending upon the stream section, from 23 to 53% of the fish were caught within the first 16 days after the season opened.

Fish caught that were reported released:

Black River--68-63%

Castor River--84-74%

Courtois Creek--88-94%

Current River, Big Spring area--80-79%

Current River, Powdermill area--73-71%

North Fork--72-82%

This shows that most anglers do release their catch, but catch and release did vary quite a bit depending upon the stream section. They attributed the much higher release rate on the lower section as opposed to the upper section of Current River as due to the greater number of tournaments in the Big Spring area, with tournament anglers releasing their catch.

Percentage of tagged fish harvested annually:

Black River--23-24%

Castor River--10-26%

Courtois Creek--10-5%

Current, Big Spring--13-15%

Current, Powdermill--26-26%

North Fork--15-10%

Quite a range of the number of fish harvested of the tagged fish, depending upon river section. Overall, fairly low numbers of fish harvested.

Adding the natural mortality to those figures above, they came up with these figures on total mortality:

Black River--55% (24% harvest plus 32% natural)

Castor River--54%

Courtois--37%

Current, Big Spring--43%

Current, Powdermill--39%

North Fork--45%

You can see that they estimated natural mortality as being quite different depending upon the river system, and I still haven't been able to figure out where they got those figures. For instance, the Powdermill section had 26% harvest mortality, but only 13% natural mortality, while Courtois, with only 7% harvest, had 30% natural mortality.

The aging and growth rates obtained by collecting scales was interesting. The AVERAGE size for each year class was pretty similar and typical of other studies of Ozark smallmouth. Here is the range of averages for each age:

2 years--7.7-9.4 inches (Castor River had the 9.4 average, Current River at Powdermill the 7.7)

3 years--8.6-10.3 inches (Courtois had the 8.6, Black and Current at Big Spring the 10.3)

4 years--10.0-11.5 inches (Courtois the lowest, Black the highest)

5 years--11.3-12.8 inches (on Castor and the two Current stretches, these fish averaged over 12 inches)

6 years--12.3-13.9 inches (Black River had the lowest, Current at Big Spring the highest)

7 years--12.2-15.6 inches (Black River actually lost ground here, while there was a large leap in size at several sites, with the Current at Big Spring the highest)

8 years--14.4-16.9 inches

9 years--14.9-17.7 inches

10 years--16.9-18.3 inches

There weren't very many fish over 18 inches captured. Largest was a 20.4 incher from the Current at Big Spring. But there were some big surprises on individual fish. Some fish were aged at being very young for their size, such as 15.8 inch three year olds from Castor and Black, 17.9 inch four year old from Black, 18.8 five year old from Black and 17.2 five year old from Courtois, 19.0 inch six year old from Black, 19.7 seven year old from Black and 18.5 and 18.9 seven year olds from Current. The biologists seemed to assume these were probably errors in the aging techniques.

Now to the meat of the matter. They used a modeling system called "Fishing Analysis and Modeling Simulator" (FAMS) to predict the effects of higher minimum length limits on the fishery, based upon the data collected. One figure this modeling came up with was the change in pounds of fish harvested under different length limits. This modeling showed a decrease in pounds harvested under a 14 inch, 15 inch, and 18 inch length limit for every stream section except the Current at Powdermill. The decrease was always greatest under an 18 inch limit, but ranged from 21-41% under a 14 inch limit to 70-94% under an 18 inch limit, except for that one section of the Current, where it showed a 6% increase under a 14 and 15 inch limit and only a 13% decrease under an 18 inch limit.

The FAMS modeling also predicted the change in numbers of fish over 14, 15, and 18 inches per one hundred fish with each length limit...in other words, supposedly, for every 100 fish caught by anglers, how the percentage caught of each length would change. Most of these figures showed substantial increases. Courtois Creek was the least affected, with an increase of 14 inch fish of 18% under a 14 inch limit, an increase of 15 inch fish of 29% under a 15 inch limit, and an increase of 83% on 18 inch fish under an 18 inch limit. Black River was estimated to show an increase of 92%, 179%, and 1075% respectively. In effect, the numbers of fish around or above whatever length limit was imposed should increase anywhere from 30% to as much as 10 or 11 times. Castor River, in fact, showed a 2250% increase in 18 inchers under an 18 inch limit, but since they assumed very few fish ever reached 18 inches on Castor (the biggest they tagged was 16.7 inches), such an increase wouldn't really amount to much. In fact, that was their assertion overall. They said that the numbers of bigger fish were so small per hundred fish caught that even if they doubled or tripled, it would only mean anglers would catch 2 or 3 fish over 15 inches for each hundred they caught, instead of one fish over 15 inches, and anglers wouldn't really notice that increase.

Their final recommendations were that the current regulations were fine on every stream section except the Current around Powdermill, since any increases in length limits would result in decreases in pounds harvested and the increases in size of fish caught per hundred would not be very noticeable. On the Current around Powdermill, the high harvest rate and low natural mortality, combined with growth rates, showed a higher length limit would benefit the fishery. They saw little difference between a 14 inch and a 15 inch length limit, and considered an 18 inch limit to be in effect a catch and release regulation. They said that angler surveyes showed no support for catch and release regs, so the 18 inch limit was dismissed.

Now...I have a bunch of questions with the report and its conclusions.

1.The figures for Current River at Powdermill are WAY different from the other sites. They showed a yield in pounds harvested for this section under the current regs as being 51.96 pounds per hundred fish. The closest any other section came to that was 10.28 pounds for the other section of Current River. Not only that, but they showed the number of fish over 12 inches per hundred in that section to be 46%, the next highest was something like 12%. When starting out with those figures, that section already looks to be very, very good compared to the others. Was that really true, or was there an error either in sampling or compiling data somewhere?

2. Why the emphasis on pounds harvested? Is that really the main goal, or is the goal to produce more big fish for anglers to catch? Either you believe the figures that only a small percentage of anglers harvest smallies, in which case it follows that much greater numbers of anglers don't consider harvesting important and would presumably be happier with more big fish; or you believe that in spite of those numbers, most anglers want to be able to harvest meat. And as far as the angler surveys mentioned that allegedly showed no support for catch and release regs, Dan Kreher of the Smallmouth Alliance has pointed out that there was a question on the surveys asking something like, "What percentage of smallmouth streams would you be happy with some smallmouth harvest allowed?" 66% of respondents said anywhere from 0% (all of them should be catch and release) to 75% (which meant that they were okay with 25% of the streams being catch and release). So 2/3rds of anglers surveyed apparently had no problem with some stream sections being catch and release--or an 18 inch limit, which the biologists said they considered to be virtually catch and release.

3. What about that natural mortality? Where did those figures come from? And wouldn't it be likely that smaller, younger fish would suffer more natural mortality, due to more predators and less experience in escaping and avoiding dangers, than older, bigger fish? Wouldn't it then be likely that you'd get more return on protecting bigger fish because fewer of them would die naturally each year? And what's up with the extremely low natural mortality figure of that one section of Current River compared to the others?

4. They didn't consider lowering the creel limit at all. While this would very likely drop their vaunted harvest in pounds figure even more, it seems to me that, in conjunction with the higher length limits, it would give you a lot more bang for the buck on increasing numbers of bigger fish.

5. They dismissed any idea of slot limits, saying that they couldn't see where a slot limit would result in increases in growth rates, and experience on small public lakes have shown that anglers don't keep many fish under the slot anyway. Again, what's the goal, here? Is it to maximize pounds harvested, or move the size structure toward more big fish? It seems to me that a slot limit of 14-20 inches or 14-18 inches would be the best protection for the14-18 inch fish, resulting in more big fish, while still allowing enough harvest of under 14 inch fish to give those who want a meal or two.

6. And what about those variations in size among age classes? If true, and not just errors in aging, it could mean that some fish in these rivers have better genetics for growing big. A slot limit would protect them while they were good sized but still young and dumb, while cropping off a lot of the much slower growing fish. It MIGHT result in better genetics down the road.

I don't think you can quibble much with their conclusions IF you assume that harvest is still the main goal and IF you assume all the figures to be accurate. But some are estimates that I don't see much support for. And if the goal is to move the size structure of the population toward more big fish, it becomes a different ball game.

[Mitch f]

I can only dream that your number 6 is not an error in the aging process and there are still genetic giant genes swimming around. But honestly, those growth numbers are SO different that I'm sure it's not right. an 18.8" 5 yr old is more than twice the normal growth rate.

[fishinwrench]

So after all of this what have we learned?

I don't feel any smarter than I was before the study and I am not expecting any regulation changes...so what was the point, other than giving a group of biologists something to do ?

[Old plug]

I do not know Mitch why it would not be possible. My dad knew and went to school for some time with the Alton Giant. I guess anything is possible. It was only one fish. He was only one man.

[Gavin]

No time to digest that. Think we are gonna get something though. Thinking harvest is way understated. The sample size was tiny but it yielded some interesting results. think a few very good C&R anglers took a bunch of MDC tag money on some those creeks. Odd selection to. Have fished all of the tag water. None of it on my A list.

[Ham]

The MDC report is interesting to read and fun to think about. The science part isnt easy, It isn't cheap, and it isn't perfect. The research seems to pose to me more questions than it answered.

Here's the deal though. Likely, most fishermen don't look at fishing the way we do or at the very least the way I do. I would not keep a smallmouth to eat if I was starving to death. I just wouldn't. I'd catch panfish or crawfish or suckers or catfish. Smallmouth are just too much fun to be caught once. I go fishing to enjoy myself and relxa. I am not on the creeks lookng for food. Some (lots?) people are. So, the MDC is always going to have to manage for different user groups with different desires. I'm pretty confident they can look at the data and make some concrete changes for beter fish management IF what was best to have more and grow bigger smallmouth was the only concern, but sadly, it isn't the only concern.

Before we need new regulaions, we need more agents to enforce them. We need more people to read and be aware of them. And we need more people willing to follow the regs because its the right thing to do and NOT because they are afraid of a ticket.

[SpoonDog]

A whole lot goes into growth rates, especially when you're looking across an entire watershed and between different systems. Fish in one reach may have better habitat or a denser prey base than fish an another. Even mortality or harvest rates can effect growth- high mortality frees up resources for the remaining fish, allowing them to get bigger, faster. It isn't always as easy as saying "the big fish have better genetics, so we need to protect those."

[fishinwrench]

So can we just demote all these biologists back down to agents, and put them out there enforcing the rules that were written long ago, instead of STUDYING for new rules that still won't be enforced?

[mjk86]

Im really surprised at how high the percentage of smallmouth caught and reported was, idk if thats good or bad? I think your answers to 1, 3, and 6 might all be related. They have to make massive assumptions with mortality rates, every body of water has so many unique variables that cant all be accounted for individually, but must be grouped together. When you have 100 variables, each one having a range of values, you make an assumption by averaging the ranges. This way you have a value to plug into the model, that value however is quite limited, as any individual measurement may have all 100 variables at one extreme end of the range. Most measurements will fall perfectly within your averages, but if you happen to be there on the wrong day, or pull the wrong sample all of your measurements will be on one extreme end of the spectrum. This could have been what happened with the current...or maybe i just need to go fishin there. Seems like lowering the creel limit would be the best way to make a larger population of larger fish, but then again with the low percentage of harvest anglers, and the overall slow growth rates of smallies in ozark rivers its more likely that there would just be more small fish. In regards to number 6 I think that genetics plays the main role in growing big fish. Look at a classroom full of kids, all of them about the same age, but large variation in size.

[mjk86]

So can we just demote all these biologists back down to agents, and put them out there enforcing the rules that were written long ago, instead of STUDYING for new rules that still won't be enforced?

No we cant.