Researchers have shown that vulnerability to angling is a heritable trait. They have demonstrated that selection of low vulnerability to angling lessens vulnerability with each successive generation (to date up to 4 generations that I am aware). Here are a couple references demonstrating those findings.
It is interesting that selection can do more to lower vulnerability than it can to increase it. In the first paper this is depicted nicely on page 194 (journal page). They express total catch rate (TCR) in (catches per hour) per (fish density). Their fish density is individuals per hectare. And the value for the parental population is .0136 fish/hour/(individuals/hectare). So one could multiply this number by the fish density to understand the average catch rate. In a balanced pond with 123 LMB/hectare (50 LMB/acre), the expected fish catch rate is 1.67 fish/hour or an effort of 35 minutes per fish. The TCR for density in acres is .03332.
They were able to improve the catch rate by selection in successive generations by selecting fish caught more than 3 times to be parents of the next generation. The first generation change was pretty dog gone good but the second and third generations had much more muted effect. Fishing catch rates for a density of 50 LMB/acre for the Parent, 1st Gen, 2nd Gen, and 3rd Gen were 1.67 fish/hr, 1.84 fish/hr, 1.89 fish/hr, 1.93 fish/hour, respectively. So after 3 generations the catch rate improved by 15%.
On the other hand, selecting for low vulnerability to angling has an opposing more profound effect. Low vulnerability was selected on the basis of having never been caught. Fishing catch rates for a density of 50 LMB/acre for the Parent, 1st Gen, 2nd Gen, and 3rd Gen were 1.67 fish/hr, 1.30 fish/hr, 1.09 fish/hr, .85 fish/hour, respectively. So after 3 generations the catch rate worsens by 49%.
I have once read that catch rates of 1 fish/hour are considered good fishing by most people and all of these numbers are in the neighborhood of that number with a balanced population density of 50 LMB. We are talking vulnerability to artificial baits and these studies do not test or consider vulnerability to live baits. I can tell you from experience that LMB in our local intensely fished community lakes and ponds are vulnerable to live bait but are much more difficult to catch on artificial bait. In as much as that is true, live bait is an option for removing fish that may never be caught on artificial bait. Such may help with efforts to select for high vulnerability.
In the first paper above they had a good practical method of marking captures. They would clip the top 1/3 of a dorsal spine beginning with the second spine and moving posterior with each succeeding capture. I consider this a quick and dirty way record catches so that one could select for easier to catch individuals. Perhaps the best sizes to record captures are for LMB in 8" to 12" range. As they become adults >12" one could select for spine clips of 3 or more and do a different kind of fin clip to mark that fish as selected for the adult population.
On the other hand, selecting for high vulnerability does not improve catch rates much above the parent population. So it might be a whole lot easier to buy recruits which are not selected on the basis of vulnerability. IOWs you may not notice the difference 15% improvement makes and it would be a practical source of adult recruits with acceptable catch rates. Just seems to be an option. So one could fin clip those recruits and remove any fish >12" that isn't fin clipped making some effort to use live bait to catch low vulnerability recruits produced in-situ by natural reproduction. I guess which approach a person might take would depend on personal preference but the cost of 12" recruits is low enough in relation to time and other costs to be a non factor for most.
Last edited by jpsdad; 08/31/2412:01 PM.
It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers
Pretty interesting JPS. I can see how this might apply on the hatchery level. I'm trying to wrap my head around how this could apply small scale to an owner's pond annual culling efforts. The males pretty much gotta go, and with efforts to remove fish on a slot through catching them. How would a pond owner catch, clip and return while maintaining pond goals and management efforts?
1.5acre LMB, YP, BG, RES, GSH, Seasonal Tilapia I subscribe to Pond Boss Magazine
One thing that spoke to me in the second paper was that 25% of the population of the parental group were not caught at all. From the perspective culling wouldn't we want fish that are inclined not to take artificial bait to go? In a practical sense, its not likely that culling such fish could be accomplished adequately by sampling with artificial baits. You have to capture them to cull them so to speak. IMHO, if vulnerability to angling is important to you, you will have to use this trait as a decision variable when culling and you will have to employ sampling techniques that hard to catch fish are vulnerable to. So fishing with live bait and shock surveys would both provide a means of sampling fish that you have never caught with artificial bait.
With your goals, yes, the males do have to go. But this would not apply to a balanced pond seeking better growth of panfish or a Big BG pond. A person needs both sexes represented in the latter two scenarios. A person does not need males at all in a Big Bass scenario if he is willing to purchase new female recruits. There is more value in that than a person may realize. If sub-adult LMB are not present, then there will be more forage for the adults and they will attain greater ultimate weights and growth as a result.
You will need to combine culling of the original stocking and adult recruitment to maintain a fishery that can produce trophy LMB 12 years from now. This combination of culling and recruitment should eventually merge with a recruitment plan where only chosen recruits are allowed to live when caught. If as Lusk says, "A WELL MANAGED POND CAN SUPPORT 80 LBS OF LMB", then you have to keep the population of LMB below 20 to consistently produce trophies. If you want something that is sustainable and an easier to maintain, these 20 must be spread across multiple years of recruitment. So that is the challenge. Going from 1 year class to 7 years of representation .... that is the goal IMHO.
Reach out by PM and I will share my thoughts on this with you.
Last edited by jpsdad; 09/01/2404:03 PM.
It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers
This has been covered at length both on the forum (search "catchability") and in PB mag. There are multiple studies on the subject (not just the ones above) both on the experimental and applies science aspects (lab and real-world lakes etc). Does someone have a question to be answered. It can all be exhibited in one chart (don't need all the statistics). Below is the chart.
I did not realize that "catchability" was such an inheritable trait.
For someone with a well-balanced pond that does not require supplemental stockings, the target fish are going to become much more difficult to catch over time!
So the question I would pose is, "How could you reverse/slow that trend by selection in your balanced pond?" Is it possible to do it? What is(are) the practical method(s) that can accomplish that goal?
It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers
Not an easy issue to manage. Bill posted did a PB article with IIRC Dave Willis on practical options. One method is don't take out the fish caught by angling. Instead, assuming you electrofish , take out a random sample then. Again, there is a lot here on "catchability" and or "aggressiveness".
So the question I would pose is, "How could you reverse/slow that trend by selection in your balanced pond?" Is it possible to do it? What is(are) the practical method(s) that can accomplish that goal?
I think a grow-out or brooder pond would be an excellent resource.
Take the aggressive and larger than their class peers fish that you catch, and put them in your small brooder pond. (Let them spawn in there and then stock a few of those fish back into your main pond.)
Use the traits of the aggressive shooters to improve your population genetics, rather than the opposite - which probably occurs in most fishing ponds.
I would agree with the brooder pond (fish replacement or augmentation) approach. But that IMO is a - lot of management work approach and is why I provided - "Not an easy issue to manage.". It can be addressed but it takes working diligently on the issue.
For those who can't have brooder pond, being diligent to clip a dorsal spine of fish caught on artificial lures can identify fish that one can retain as adults. To prevent brooding by fish never caught on artificial lures, one could try to remove them preferentially by fishing for them with live bait or electrofishing if that is an option. Return spine clipped fish you want to breed. Removing fish that one cannot catch on artificial lures will have the most profound effect of diminishing Low Vulnerability inherited traits.
IMHO, no management plan is complete without planned recruitment of a core adult population that is consistent with goals whether "big bass" or "balanced". Recruitment should take into account natural mortality whatever is a good assumption as an average for adult fish under catch and release. For example, for LMB >12", if one expects average annual mortality for recruits of this size to be around 10% for the subsequent 10 years. A recruitment rate of three 12" fish to the acre each year with 10% natural mortality is an annual population of 20-21 adult fish (perfect for growing large LMB in a moderately productive pond) ... assuming no fish live more than 10 years after selection at 12". So in the context of a recruitment plan conducive to vulnerability to angling, this core recruited population are spine clipped LMB that have been caught on artificial lures (or possibly supplemented or supplied from a brooder pond as FishingRod suggested or a fishery supplier whose fish are not subjected to angling selection). IMHO, the core population that is to be catch and release should carry an additional fin clip so that it is easily identified to be one the fish which comprise the core adult (brooding) population.
I agree with Eric. Vulnerability to angling is challenging. Because under most circumstances, LMB recruitment is excessive without removing fish. You can't meet goals without capturing and removing them and low vulnerability individuals can be problematic. Aside from not enjoying catching them or easily removing them, they become a headwind that must be overcome to grow the fish you can catch. If they number too many they will cause slow growth.
There is one other thing we should probably consider. Even high vulnerability fish can become difficult to catch. They learn to avoid artificial lures and become harder to catch over time. Restricting lifetimes can allow one increase the population of selected adults and/or increase annual growth rates with out increasing the forage required to support the population. The population changes at a greater pace with new fish with less experience in the art of avoiding anglers taking the place of older more experienced fish. Other advantages of restricting lifetimes can be greater growth rates, and better condition on the same quantity of forage.
For example, 3 12" recruits per acre-year living no more than 10 more years and undergoing 10% mortality can grow to 7.85 lbs (.66 lbs gain/year) on 382 lbs/acre of BG forage annually. Average condition should be in the neighborhood of 111. This much forage supports a population weight of 79.66 lbs/acre of LMB. The population of adult LMB is 20-21 fish per acre.
Alternatively, 4 12" recruits per acre-year living no more than 6 more years and undergoing 10% mortality can grow to 7.25 lbs (1.0 lbs gain/year) on 379 lbs/acre of BG forage annually. Average condition should be in the neighborhood of 129. This much forage supports a population weight of 79.98 lbs/acre of LMB. The population of adult LMB is 20-21 fish per acre.
Both scenarios produce similar top end weights of fish. Both scenarios are equivalent in terms of the biomass of LMB supported. Reducing ultimate lifetimes reduces the amount of forage used for maintenance and increases the amount of forage used for adding weight. So more weight is being produced annually. But for the topic of hook-smart fish ... fish that you have caught that have become smarter ... the approach of limiting lifetimes keeps fresher, younger fish.
Last edited by jpsdad; 09/07/2406:45 AM.
It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers
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