Pond Boss Forums FISH & FISHING Sunfish-Including Largemouth and Smallmouth Bass "Bass Backlash"

I'm reading an article in Scientific American about the genetic response of smallmouth bass to electrofishing in Little Moose Lake in the Adirondacks in New York. A Liam Zarri studied SMB eradication work at Little Moose; his results are published in Proceedings of the National Academy of Sciences USA. It appears that culling SMB in that lake using electrofishing has led to the population tending towards reproducing at younger ages and smaller sizes, thwarting the eradication attempts.

Maybe ewest will read and decipher for all the rest of us what has been written and published in the study. Fascinating example of unintended consequences.

There is a confusing reference to native lake trout in the SA magazine article. My guess is that is some sort of editing mistake.

That is a beautiful lake we have kayaked and canoed a few times. There are so many nooks and crannies in those lakes, I don’t see how eradication of a single species would be possible.

If you think about it. It should not be a surprise. Large bull BG inhibit smaller BGs from breeding & taking the best spawning areas. Large males will accept a small female if she is ready to spawn. The bigger fish are most likely to pass on the best genes. If there are no big fish, then survival of the species takes over & the little guys get their chance.
At best they may be able to keep the SMB at bay giving the trout a better chance & perhaps over MANY years get the SMB under control. Yes , till some really smart angler that knows everything bucket stocks the lake again.

Do you have a link ?

Sorry Eric, no I do not have a link to the Proceedings article. I came across the reference to it in the article on pages 11 and 12 of November 2025 Scientific American. The studies originated at Cornell U. Mr. Zarri is now a molecular ecologist at the Smithsonian National Zoo and Conservation Biology Institute.

https://www.scientificamerican.com/...ade-electric-culling-in-adirondack-lake/

This should be the article he is referring to.

The article says that the purpose of culling the smallmouth is to restore a healthy lake trout population. It says that Lake Moose used to be able to produce 35 lb trout but, since the invasion of smallmouth, they are stunted and have become uncatchable.

Read the article posted. Can't tell much from the overview to the real study.

Here is the real study but I don't have access to it in full

Canadian Journal of Fisheries and Aquatic Sciences Volume 65, Number 10, October 2008Overcompensatory response of a smallmouth bass (Micropterus dolomieu) population to harvest: release from competition?
Research Article
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Overcompensatory response of a smallmouth bass (Micropterus dolomieu) population to harvest: release from competition?
Authors: Elise F. Zipkin (email: [email protected]), Patrick J. Sullivan, Evan G. Cooch, Clifford E. Kraft, Brian J. Shuter, and Brian C. Weidel Authors Info & Affiliations
Publication: Canadian Journal of Fisheries and Aquatic Sciences
7 October 2008
https://doi.org/10.1139/F08-133

Abstract
An intensive seven-year removal of adult, juvenile, and young-of-the-year smallmouth bass (Micropterus dolomieu) from a north temperate lake (Little Moose Lake, New York, USA) resulted in an increase in overall population abundance, primarily due to increased abundance of immature individuals. We developed a density-dependent, stage-structured model to examine conditions under which population control through harvest could result in the increase of a targeted species. Parameter values were derived from a 54-year data set collected from another north temperate lake (Lake Opeongo, Ontario, Canada) smallmouth bass population. Sensitivity analyses identified the demographic conditions that could lead to increased abundance in response to harvest. An increase in population abundance with harvest was most likely to occur when either (i) per capita recruitment at low levels of spawner abundance was large, juvenile survivorship was high, and maturation of age-4 and older juveniles was moderately high or (ii) per capita recruitment at low levels of spawner abundance was slightly lower, yet the maturation rate of age-3 juveniles and adult survivorship were high. Our modeling results together with empirical evidence further demonstrate the importance of overcompensation as a substantial factor to consider in efforts to regulate population abundance through harvest.

Here is an update study on the same issue

Littoral Fish Community Response to Smallmouth Bass Removal from an Adirondack Lake Get access Arrow
Brian C. Weidel, Daniel C. Josephson, Clifford E. Kraft
Transactions of the American Fisheries Society, Volume 136, Issue 3, May 2007, Pages 778–789, https://doi.org/10.1577/T06-091.1
Published: 01 May 2007
Abstract
Large‐scale observational studies in eastern Canada and the northeastern USA have concluded that introduced littoral predators are responsible for reductions in native fish diversity and abundance. To determine whether nonnative predator removal could increase native littoral fish abundance, we removed 47,682 smallmouth bass Micropterus dolomieu from a 271‐ha Adirondack lake during a 6‐year period. Two years after removal began, habitat‐stratified snorkel surveys indicated a greater than 90% reduction in smallmouth bass abundance. The relative abundances of six native littoral species increased (4‐90 times preremoval abundances) within 2 years of smallmouth bass removal. Decreased relative predation risk during the experiment reflected the reduction in littoral predators and identified seasonal differences in nearshore predation risk. The smallmouth bass population was resilient to removal, producing strong year‐classes throughout the experiment. Mechanical removal was successful at decreasing smallmouth bass abundance and increasing native fish abundance, but removal must be conducted on a yearly basis to maintain low smallmouth bass population abundance. Our results provide experimental evidence regarding the need to prevent littoral predator introductions in Adirondack waters and offer support for nonnative control wherever native fish species conservation is a management priority.


Here is a PB article that might interest you.. Subscribe to PB mag.

The Cutting Edge - Science Review


Evolution in Ponds – Fast and furious?



We all learned in high school science class that the process of evolution was slow. Like thousands of years slow – right? There is some recent news – as to pond fish species at least that we were dead wrong. Evolution can be fast and furious, as in less than three years fast and furious as the emotion experienced when our stocking/management efforts go down the drain. Evolution is not always good and it can have very profound negative consequences. Ever wonder how with a pond full of fish you can fish for a few hours and only catch one or two fish? That can be due to human induced selection (speeded-up evolution) through fishing, often referred to as non-catchability or hook smart fish.


Many of us initially ignored reports of fast evolving fish mostly because it is contrary to what we all learned in school. Frankly I did not believe what I was reading from one early source study because it seemed to be political and was about a saltwater bait fish. Then a few more pieces of the puzzle came to light. We discussed them on the Pond Boss Forum but only in a related way being Florida strain bass vs Northern strain bass and catchability. Then more works appeared on how fishing could cause rapid genetic change not only in catchability but also in reproduction, growth, aggressiveness and size. Those studies were reported on in this column in one form or another but the big picture was yet to become clear. More and more pieces of the puzzle fell into place – at least enough that even I could connect the dots.


This issue reviews two new and related studies from small Connecticut waters. These two studies reference and tie together studies which previous Cutting Edge articles reviewed. The new studies are titled, Loss of Naivety to Angling at Different Rates in Fished and Unfished Populations of Largemouth Bass by Jan-Michael Hessenauer, Jason Vokoun, Justin Davis, Robert Jacobs & Eileen O’Donnell in Transactions of the American Fisheries Society, 145:5, 1068-1076, @ American Fisheries Society 2016 and Can Largemouth Bass Transplanted from an Unexploited Population Genetically Contribute to an Active Fishery? A Test Case for Genetic Management of Exploited Fish Populations by Jan-Michael Hessenauer, Jason Vokoun, Amy Welsh, Justin Davis, Robert Jacobs & Eileen O’ Donnell in the North American Journal of Fisheries Management 37:271–283, 2017 © American Fisheries Society 2017. The studies explain the rapid evolution problem and provide a temporary solution the supplemental stocking of new genetics, which many in the Pond Boss family have been using.


Over the course of a single growing season angler catch rates are known to decline even after accounting for fish density and mortality from angling. Studies of several species have indicated that reduced catch rates are due to adapted learned lure avoidance which can quickly become genetic. Catch and release angling used by many pond owners provides fish the opportunity to learn to avoid lures through direct experience and via social learning. We should have known this based on stocking (habituation) studies proving that predator avoidance is known to be learned by fish .Catch-and-release angling provides fish a direct negative learning experience and rarely results in mortality. Fish live another day but adapt and learn lure avoidance. Keep in mind that these biters are the aggressive fish which are now less apt to bite again. In addition the non-biters learn lure avoidance from watching which reinforces the negative man made selection process. In short fishing is selecting (encouraging) the fish not to bite. On the other hand if we remove the fish we catch we have removed the best most aggressive fish, speeding up the bad genetic change. For pond owners this is a lose-lose proposition. Because non-catchability in recreational angling has been demonstrated to be an inherited trait over time (a couple of years) we can quickly have a pond full of non-catchable fish.


SEE BELOW


FIGURE 2. Predicted and observed catch per effort (CPE) for Largemouth Bass originating from fished (solid line, filled squares) and unfished (dashed line, open circles) populations at the average water temperature (20.7°C) during angling trials as a function of cumulative catch events

This chart from the first study above reflects the large drop in catch rates over a short time (3 months) under controlled conditions. In this study 56% of the fish were initially uncatchable by lure and both newly added fish and existing fish quickly learned lure avoidance to the point of a near zero catch rate over 3 months. These types of results were also exhibited in other studies by Philipp, Garrett and others.

Here is another one.

THE CUTTING EDGE – SCIENCE REVIEW




Adaptation (environment) vs. Evolution (genetics) in Fish


On The Pond Boss Forum recently there have been discussions on adaptation vs. evolution. This conversation centered around how do fish change, what is the mechanism (environment or genetics) and how long does it take. In Science Class we all learned about Darwin’s theories regarding Evolution. We were taught that Evolution is a slow gradual process. Darwin wrote, "…Natural selection acts only by taking advantage of slight successive variations; she can never take a great and sudden leap, but must advance by short and sure, though slow steps." Parts of Darwin's Theory of Evolution are now a theory in crisis in light of the recent tremendous advances in molecular biology, biochemistry and genetics. Darwin’s prediction was right on a geological scale (Earth’s age) but it has since been shown that evolution of species can happen much faster. In bacteria and insects, single generation change is known to occur. In more advanced species (fish and larger creatures), it was thought that things are more gradual, but still, do occur in sudden bursts.

While evolution was thought to be a slow process adaptation refers to the relatively quick process where through phenotypic plasticity certain groups or individuals change to be better suited to their environment and habitat. The thought is change is needed quickly so that they can survive and maintain normal function. In a prior Cutting Edge issue we discussed this concept described in The Effect of Vegetation Density on Juvenile Bluegill Diet and Growth in the Journal of Freshwater Ecology 2012, 1–11 by Daniel E. Shoup, Michael A. Nannini and David H. Wahl.

In that study environmental conditions during early Bluegill development shaped individuals’ phenotypes so they were more adaptive to the conditions they encountered. Plasticity has been shown to effect sunfish (Lepomis) shape, feeding and behavior in some cases. Here, by the end of the three month experiment, bluegill from the low vegetation ponds were significantly longer – twenty (20%) percent than bluegill from the high vegetation ponds. Were the long bluegill that fed in open water that way because longer fish can swim better in open water and were the shorter bluegill that way because being short allows them to maneuver around the weeds better? In this case a clear finding of adaptation in Bluegill in only three months.

Adaptation (through phenotypic plasticity) is the emergence of new characteristics in order to best suit the changes in the environment or habitat. Adaptation arises at the phenotypic level under the influence of environmental factors on the expression of the existing genes. It has become increasingly clear however, that phenotypic plasticity actually represents a fundamental component of evolutionary change. More questions arise like - what time period is required and what is the mechanism to get from adaptation to genetic change? Now some new thoughts – that genetics can be changed in early development through environmental influences. Similar to what we saw in the above study on Bluegill.
A recent study titled, Using Teleost Fish to Discern Developmental Signatures of Evolutionary Adaptation From Phenotypic Plasticity in Brain Structure by Zachary J. Hall and Vincent Tropepe in Front. Neuroanat. 14:10, 18 March 2020 is illustrative. This study looked at brain development in Teleost fish (ray-finned fishes) like those common in ponds.
In the past the impact of evolution on the brain has been studied by comparing the sizes of brain regions between species or in some cases in the same species. However, more recent work has demonstrated that environmental factors, such as sensory experience, influence brain region sizes intraspecifically (in the same species). This brings into question the distinction between evolution (genetic) and adaptive (environment) sources of brain anatomy variation in fish species.
The authors examined how newer fish research indicates the capacity for the environment to shape brain structure similarly within a species. Some of the first evidence demonstrating the capacity of the environment to shape fish brain structure came from comparisons between related wild-caught and lab-reared fish populations. The noted studies finding Salmon reared in a hatchery exhibit reduced olfactory bulb (smell function) and brain size compared to age-matched wild salmon from the same genetic cohort and also finding that first generation female guppies reared in the laboratory from wild parents exhibited reduced fore-brain and vision processing compared to wild-caught fish. Because the laboratory environment generally lacks much of the sensory stimuli animals would encounter in the wild, these findings suggest that brain development in fish is influenced by sensorimotor experiences. In another study both male guppies collected from regions of high predation and laboratory-reared male guppies exposed to sight and smell predator cues during development have larger brains as adults compared to unexposed males.

Another more recent method of studding fish brain development has been to compare fish populations of the same species inhabiting different environments. These studies revealed habitat-dependent brain size findings similar to studies comparing lab- and wild-bred populations. For example, whole-brain size is larger in sunfish that occupy a littoral shoreline habitat vs. those that live in a pelagic habitat.
The discovery of continuing adult brain neurogenesis in mammals demonstrates that adaptive processes continue to shape the brain well beyond embryonic development. Because fish exhibit extensive neurogenesis in the brain throughout life as compared to mammals it is more likely a life-long process for brain growth in fish. These developments in embryonic and whole life brain development in fish resulting from environmental conditions (adaptation) is proof that adaptive change (through phenotypic plasticity) is quicker , more powerful and far more prevalent than previously thought.

For those interested in generational genetic vulnerability of LMB to angling discussed in the Forum here is the summary of the article that has been discussed

Selection for Vulnerability to Angling in Largemouth Bass by David P. Philipp et.al
Abstract
Although a great deal of effort has been expended to try to understand the consequences of fishing-induced selection by commercial fisheries, relatively little effort has been put into trying to understand the selective effects of recreational angling. We conducted a long-term selection experiment to assess the heritability of vulnerability to angling in largemouth bass Micropterus salmoides. Three successive generations of artificially selected largemouth bass were produced from a single experimental study population. Within each generation, individual adult largemouth bass were identified as having either high or low vulnerability to angling through a series of controlled catch-and-release angling trials. Individuals of each vulnerability group (high and low) were then selected from that population for breeding to produce the next generation. The response to selection for vulnerability to angling increased with each generation; that is, the magnitude of the difference between the high- and low-vulnerability groups of fish increased with each successive generation. Realized heritability was calculated as 0.146 (r2 = 0.995), indicating that the vulnerability of largemouth bass to angling is indeed a heritable trait. Our results indicate that recreational angling has the potential to alter the gene pool of wild fish populations, which may indirectly affect population characteristics such as survival, growth rate, and reproductive output as well as directly affecting angling success rates.

In summary to repeat what ewest has posted:
"Catch-and-release angling provides fish a direct negative learning experience and rarely results in mortality. Fish live another day but adapt and learn lure avoidance. Keep in mind that these biters are the aggressive fish which are now less apt to bite again. In addition the non-biters learn lure avoidance from watching which reinforces the negative man made selection process. In short fishing is selecting (encouraging) the fish not to bite. On the other hand if we remove the fish we catch we have removed the best most aggressive fish, speeding up the bad genetic change. For pond owners this is a lose-lose proposition. Because non-catchability in recreational angling has been demonstrated to be an inherited trait over time (a couple of years) we can quickly have a pond full of non-catchable fish."

This is in-line with the contexts shared in the "Must Read" thread. It doesn't take a high standing population of SMB to produce substantial year classes of offspring. Reducing adults can help to reduce the predation mortality of SMB that are below recruitment lengths. So it can be difficult to reduce the production/survival of SMB offspring by removing SMB adults. The same applies to any fish. This includes BG. One cannot cause the production of YOY to suffer by removing BG that are too large to eat.



Stop and consider this:

If non-catchability is an inheritable trait, then why did selected fish that did not prove vulnerable to angling (were not caught) have offspring that were in fact vulnerable to angling?

Doesn't make sense, does it? That is, that "not being caught" is a trait that can be inherited. If that were true, the offspring of fish that were apparently invulnerable would not have been vulnerable at all. Vulnerability (or catchability ... let them mean the same) is heritable. So the fish that were not caught of the parent generation were not non-catchable ... they were vulnerable (or catchable) to a lesser degree. This is evidenced by the fact that their offspring were indeed vulnerable (or catchable) to a lesser degree than the parent generation.

FWIW. I believe that LMB definitely can learn hook/lure avoidance and that some are more vulnerable than others. These are important to catch rates in any BOW. The first, I believe, is the most powerful influence. Why? I regularly fish ponds that are subjected to insane levels of fishing effort. Every year, I observe a peak of catch-rates in spring that rapidly decline as the fishing hours rapidly increase for the year (The vast majority of which are not mine but others). From this experience, I discern that the winter rest does them good and helps to make them more vulnerable than they were after 6 months of persistent fishing pressure. Another influence is population density. Philipp, etal normalize catch-rates by this variable ... and I do believe this is very important. In my favorite pond, I have done monthly shore surveys for several years and the number of LMB sighted has been declining where the curve that best fits the data indicates the population is ~50% of what it used to be. So part of the catch rate that I experience there is this influence alone.

With regard to the heritable trait of vulnerability ... little is known about what is actually inherited. There have been a number of studies that have sought to discover what other traits may be selected when vulnerability is selected. The jury is still out, although some cooccurring traits have been suggested. It could be something as simple/complex as the inability to determine whether an artificial item is not food. Or it could be behavioral, for example, LMB that might pursue and consume mostly in darkness may less vulnerable during the day when folks are fishing. The point is, there is alot to be learned about vulnerability that we do not yet know.

I have personally given a lot of thought to vulnerability and how I will manage it. To lessen the deterioration of the trait, fish that have proven vulnerable to artificial lures should be selected so that the trait can be inherited. A pond only needs a limited number of LMB, if the trait is important to one, he should try to limit his population to fish he has caught on artificial lures. To lessen the impact of those less vulnerable, he should remove them by alternative methods of removal. Fishing with live bait or electro-fishing, for example. Possession is 9/10 of the law. If LMB of higher vulnerability are selected to be those adults that reproduce, then their vulnerability trait will pass to future generations. To effectively manage in this way, one must be able to identify LMB that have been caught on artificials by some system of marking. If an LMB is caught without the identification by live bait or electrofishing, then there is less risk that the LMB removed was highly vulnerable to angling. It is more likely, given sufficient cumulative fishing effort with artificials, that the unmarked LMB be of lower vulnerability.

Finally, with regard to the chart depicting the decline of catch-rates. Down there in the far right, especially later in the warm season, that is my experience in the pond described above when fishing with artificial lures. Fishing pressure has a huge effect on catch-rates. I can catch LMB at 2 or more per hour on live BG (even to include the BG bait fishing if they are abundant). Live bait is more effective on difficult to catch LMB. The chart shows catch-rate vs cumulative catch. A better representation would be vulnerability vs cumulative fishing effort (cumulative fishing hours) per unit area). This would normalize the data in the language of Philipp, et al. It would depend on the data which may not be presented in sufficient detail to infer catchability and cumulative fishing effort. Anyways, I would like to review that paper to see if the data is sufficient for these inferences ... if someone could point me to a link where a downloadable version is available. This could serve as a model I could share with members that would model expected catch rates under various population density and cumulative fishing hours. We could also collect our own data, if people were interested in contributing data.

This characteristic of offspring that were present in the new generation of the question above is due to the natural variability of all DNA (genetics) that are produced when male and female RNA strands are combined from the 'parents' to form DNA genes. Cloning could be an exception of this concept?
It is why children of the same parents do not look exactly alike except for identical twins: varability of genetic material. There can be a pretty wide range of physical 'apparences' or genetic features of offspring from the same parents. Vulneability of family members to different health issues is just one example. To my knowledge for all populations this "fairly" wide range of differences or characterestics of 'siblings' plays an important part of evolution and a big contributor to the concept of survival of the fittest to where the survivors are able to then reproduce to create offspring. Thus this is why the "selected" fish produced some or a percentage of the offspring that still had different vulnerablies to angling. It is similar to why you have a different intelligence or IQ than your siblings. Same parents different IQ of siblings. The other extrerme example of this is a child with Down Syndrome in a family of "normal" siblings.

"If non-catchability is an inheritable trait, then why did selected fish that did not prove vulnerable to angling (were not caught) have offspring that were in fact vulnerable to angling?"

The point is over time the catchability of the population of LMB became lower and lower. If the % of catchable LMB decreases from 60% to 20% you have a problem. It is insignificant that some few offspring are catchable. That is even a decreasing % over time as well.

Not saying I don't agree with genetic variation ... because I do.

I just don't believe "non-catchability" is meaningful. Why? Because it is not measurable. It is null inherently. Vulnerability is a measurable ... and therein lies an important distinction. The uncaught fish can only pass on something that is measurable and that is what it does ... it passes to its progeny vulnerability that can be measured to be less than the parent generation. Just like ... I might add ... Philipp etal concluded in their paper.

To me, "non-catchability" is like a court argument that is pressing for a verdict. When it is applied as it has been here, there seems little concern for fidelity of the research. It's rhetorical slight of hand so to speak ... a word magician's trick ... swapping vulnerability(catchability) with "non-catchability". Honestly, I don't care what the jury decides. People often believe only what they want to believe. They cannot be dissuaded by reason. If that be the case, they are deserving of where that leads. A horse can be led to water, but to quench its thirst ... it must drink.

YES. I agree. But we need to take all this in the proper context and present the facts around the paper in a way that the authors would approve. What we are dealing with are varying levels of vulnerability. Also, fishing pressure and learned avoidance also plays an important role and when sufficient will affect catch rates more than the vulnerability described in Philipp, et al. To really understand what is going on requires a great deal of information about a pond's cumulative fishing effort, the vulnerability (as described by Philipp, etal), and finally the population density. They will all affect catch rates. There are ways to double check our conclusions by error feedback. For example, if we have identified the catchable fish by artificial lure angling ... then we can follow with electro-fishing or by fishing with live bait. More knowledge improves understanding, and it may adjust original inferences of population density.

If we just inherently draw the conclusion that the LMB in the pond are uncatchable, what remains to be done? It's kind of the end of the story. What if the population density or biomass density is low? What if the forage proportion of its potential is too large? Please just consider this, if populations of LMB are always excessive, then why did the majority of ponds with LMB in the OK Paper on standing weights have F/Cs > 10 and E_LMBs less than 15%. Why were most imbalanced and forage heavy? They were total kill and these ratios cannot hide behind catchability. This is, of course, not always the path a pond takes ... but when a pond takes this path ... we need to be able to recognize that this has happened. Exaggerated ideas about "non-catchability" definitely gets in the way discovery of this condition. It can cause us to err on the wrong side and perform the wrong management actions.