Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations When and what to start harvesting LMB

I am part owner of a 35 acre lake in Western Kentucky. It was stocked with 350lbs FHM, 14000 CNBG and 1750 RES in the spring of 2017 and them 1500 4" F1 LMB in November of 2018. All based on recommendations from this forum and Bob Lusk phone call. Fishing the lake has been great. Within two years of the stocking I was catching LMB well above the line on the RW chart although I realize now that may have been because the chart is for northern strain bass. The lake is only fished by a few people and so far has been 100% catch and release. The biggest confirmed LMB is 6lbs 2oz, with and unconfirmed 7lb 6 oz. Most fishing trips a few hours long will result in multiple catches of 5+lb LMB. The CNBG population seems numerous, but small, haven't caught one bigger than 6". Have not seen or caught a RES since stocking. Minnow traps set have not caught any FHM. There are Green Sunfish in the lake from the initial body of water that was flooded during build up. Lake has a good amount of wood cover and lily pads. Milfoil is a problem in some areas, but seems less this year. Fertility seems good. Don't have a feeding program and no interest in starting.

My question is how do I keep the good times rolling? I would like to figure out a harvest plan for the LMB so they don't get overpopulated. I also wouldn't mind growing some bigger CNBG if that's possible. I have read many of the posts on here about harvest strategies. All fish under a certain percent of the RW or all fish below a certain length or all fish under 12" until fish until number of under 12" equals 12-15". Honestly I probably haven't caught 10 LMB under 12".

The goal is a good healthy fishery with a lean towards growing big LMB. When and what should I start harvesting?

Thanks

Ken

ps You can read about the initial stocking in the "Stocking 35 acre Lake" thread

There are some experts on the forum that can give you some good "general" harvest advice that will almost certainly be beneficial to your lake.

However, an actual survey of the fish populations will yield even better data to determine the best course of action.

Your group can elect to fund an electrofishing survey. Another option is to get as many of your anglers as possible to submit catch records of length and weight.

There are many Pond Boss "nerds" that love chewing on that kind of information and giving suggestions for your lake.

Sounds like you have a great fishery right now. Good luck on your next step in pond management, and I hope your group continues to break the existing "lake records"!

Is there any budget for the lake, or spending limits?

I noted you were not interested in a feeding program. Is that budget related?

Yes, budget and just a desire to do things simply and naturally as possible.

The "group" is me and another guy, and he doesn't fish. I'm not opposed to doing an electrofishing survey at some point. Is 5 years post stocking of LMB the right time to do it? I have tried to do an a small survey of relative weights, but it seemed every bass was over 100%. Is there a better chart for southern bass and/or F1 cross? We are working on the Lake Records, I'm amazed at how fast they have grown. Can't wait to hit 10lbs.

Understood on the budget and work group.

So, you should probably have already been on some type of culling program for the LMB, and if you have not done any harvesting, it's certainly time to start.

Without any further data, some general culling guidelines could be:
1) Pull all LMB with less than 100% RW, or less than 105/110% RW if all LMB are well over 100% RW.
2) Take out all LMB under 16" unless they have a RW over 100% or higher. You could have a higher length limit if you wanted to boost more growth of the bigger LMB, say 18"

Regarding the CNBG, that seems odd that you don't catch any over 6". This may mean that you don't have adequate forage for the CNBG. I'm not sure how you can change that without a feeding program, however, if you want bigger LMB, then you really are not looking to remove forage fish that can spawn and/or be eaten.

An electroshock survey should allow you to really dial in the culling program.

Also, you may be able to add threadfin shad each year, or maybe even golden shiners.

The key is to stay ahead of any problems with population imbalance. In newly stocked ponds the original stockers are the fastest growers as there is minimal competition and lots of forage. This initial growth spurt is about 3-4 years. Then with multiple year classes you get competition and growth slows (on a whole population basis not on an individual fish basis). By year 4 you need good info on growth (RW) across all year/size classes in both predator and prey species. Best way to get this info is by keeping good records (catch/creel data), doing seine surveys and then have an electrofishing survey. I would suggest that the time is right for those questions and answers. What you have described is catching the fast-growing stocker fish which have good catchability. Catchability can become an issue so read up on that also.

Thank you for the replies. Got a little busy with some sick goats and didn't get a chance to read this. I will begin culling (eating ) any bass under 16" and will get better at checking the RW of the bigger ones and maybe cull some of them if they are well below 100% RW. What chart do you suggest using? Most of the ones I have looked at put a 16" LMB at 2.25 lbs and a 20" at 4.59 lbs. I assume there is some variance pre spawn vs post spawn. I will look into threadfin shad. I assume that is to add more forage for the LMB. Will they overwinter in western Kentucky or is that why you suggest adding every year? Will do some more fishing for CNBG, but the few times I really tried targeting them it seems like all I caught was LMB and I got tired of them trashing my Beetle Spins.

GunBoss, I may have been incorrect on the threadfin shad. I somehow thought you were further south. Down south, I don't believe they over-winter, and in KY, I don't know how they'd do during the summer or if you could even source them.

You could get Golden Shiners established starting anytime and in the spring. At a lake your size, it'd be a many thousand dollars to really have an sooner impact, IMO. I'd get adult shiners now, and frye in the spring.

Sunil, are you thinking the Shiners will be needed/valuable as another source of forage because the CNBG aren't enough? I will look into sourcing them.

Gunboss,

It sounds like you have a dominant year class in the initial stocking. Very good pond with many memorable fish in it. That said, the growth of this year class has already been limited by competition of this dominant year class so there needs to be culling even of your initial stockers.

You also need some plan for progression. Based on your comments there may be insufficient recruitment of LMB. You need annual recruitment into the 12-15" range . Your population of > 15" may be (probably is) larger than it should be. If you don't plan for progression, the dominant year class will die off without suitable replacements.

You mentioned:

I am totally not surprised by that given your population of large LMB and subdued LMB recruitment. There is nothing wrong with that BG structure for producing large LMB. You must however cull some older LMB and make provisions for recruitment. You are already 6 years into a typical 10 year LMB lifespan so you must work on that now. There is really no way to sustain what you have ... but you can shape its future which will involve annual recruitment and culling to maintain a sustainable population capable of growing trophy specimens.

Culling is a big thing and so is forage base. Structure has a big part too.

Golden Shiners, in mass quantities, are available by truck for Golden Shiners and by box shipment for GS frye. Anderson's Fish Farm does the frye shipments. It's about $300 shipped for like 250,000 GS frye. You'd need a bunch of boxes!!

Also, I don't know of fertile your water is, but maybe others could speak to fertilization as part of the overall plan.

jpsdad, what would you suggest for culling? All of the >14" or 16" or judge by RW up to 16" ? Or cull some of the bigger ones? I know I need to cull and am absolutely not opposed to eating a bunch of fresh fish.

Sunil, I will look into the Shiners. Can it be done incrementally by year or will they get decimated in low numbers? I think the alkalinity was 270 when I first stocked it. Don't remember the ph. Tested with a pool kit. Are there any kits specifically for testing ponds?

Before I suggest the remedy that I would employ were I the owner of the BOW, I would like to lay some ground work. First, your lake supports a remarkable standing weight of trophy fish. Assuming 50% survival of the original stock, there may well be 21 to 22 female fish/acre averaging say 5 lbs each. This maybe too rosy, maybe there are 16 or 10 left along with some surviving males too. If the latter is the case it is worth asking why so much mortality? One possible reason for that scenario is that some fish made maintenance and survived while others succumbed to competition and made room for the survivors to grow by dying. There is a pretty good chance the latter possibility of 20 surviving LMB of the original stocking remain. Assuming the girls weigh twice as much as the boys and equal numbers of each 20 per acre corresponds to around 75 to 80 lbs of LMB per acre(where 10 of the population are female). Now this a good standing weight of LMB ... most waters don't support that weight but I think yours does and can ... possibly more. It makes sense that recruitment is subdued particularly because abundant BG hamper spawning and because LMB YOY grow very slowly where the BG standing weights are high. A combination of competition and the length of time LMB recruits spend as forage for the big LMB greatly impacts survival of those LMB YOY that swim up. For a trophy pond, this not bad because the environment favors large LMB. This, is why you presently have a trophy pond. The head start the BG had created numbers that prohibited recruitment and the stocking rate of LMB at 43/acre limited LMB competition for prey.

Of course you can't maintain this population structure indefinitely. The original stockers will be nearly all gone by the fall of 2028 and what you would have if you do nothing is those LMB that have recruited. A sustainable trophy track would be recruitment of 2 (possibly 3 fish) into the 12 to 15" range per acre per year. Based on your earlier comments, this may not be happening. For example, for you to select 3 fish per acre year for trophy track (essentially marking the fish with a fin clip) you would need to catch 105 12" to 15" female fish per year ... something which may require catching 210 mixed sex fish per year. So if you are not recruiting at that level, you may not be able to depend on your lake for recruitment. If this is so, then the standing weight of LMB would plummet starting in earnest in about 3 years.

I haven't seen your lake and only know what you have already described. I have inferred that you stocked the ASF Tiger F1s and that the excellent catchability is related to their program of selection of aggressiveness in the Northern piece of the hybrid. I have also inferred that your recruitment of LMB into adult sizes has been muted. But to whatever extent the water is unable to recruit into adult size I do think that 1.5 year old Tiger F1s that fall into 12"-15" range would be excellent recruits. An advantage of sourcing 1.5 year old fish for this size recruit is that they have a lot of life left in them. It likely takes a minimum of 3 years possibly 4 to grow equivalent sized recruits in the lake. I think you must stock adult fish as the survival and growth of smaller fish would be very uncertain in your lake. These should be sexed where a high proportion of females are supplemented. How available are these? I don't know but you only need enough to supplement what you are able to select from your own recruitment to meet the recruitment goal. By marking fish with a fin clip or tag, you ensure their release for continued growth knowing you have sexed the fish to be female with 90% probability of correctness of the sex determination. Broom straw is a good method to make the determination. It is quick and relatively simple and is more than 90% effective.

So there is my case for recruitment and selection for trophy track ... but now about harvesting. First, yes, you need to harvest some of the large LMB. Within 5 years they will be mostly gone anyway. I think a pretty good plan would be to harvest the estimated 5 year mortality spread across 5 years of fishing. I think you probably have in the neighborhood of 10 female trophies per acre and so I would suggest harvesting up to 2 per acre per year. I would say harvest 2 fish over 20" per acre per year for the next 5 years. Restrict harvest to unmarked fish over the entire period. Let's say these fish average 5.5 lbs this year. 11 lbs of LMB will be harvested per acre. It takes 55 lbs of forage to maintain 11 lbs of LMB so this will free up that forage and the remaining LMB trophies will grow into that maintenance. Spread across 8 females trophies averaging 5.5 lbs there is potential to grow the surviving trophies by more than 1 lb per individual over the course of the next year.

I would keep good records of the weights harvested and over the next five years and in every year I would harvest no more than 18 lbs of LMB per acre but I would try to harvest at least 15 lbs per acre per year filling this remaining quota with fish less than 20" but greater than 12" that have been determined male by straw method. After 5 years of recruitment and this harvest regime I would reevaluate based on population dynamics. At this point you may be in a position to harvest only unmarked fish and allowing selected recruits to go through a full life cycle as catch and release. Of course selection and recruitment efforts will be on going along with the 18 lb/acre harvest limit. Growth of recruits may suggest the recruitment rate should be increased/decreased or that harvest should be increased. I think your lake has a pretty good chance to maintain trophy status because the BG population appears to be restricting LMB recruitment and providing forage that can support in excess of 70 lbs/acre of adults. So long as the number of adult LMB/acre remains less than 20/acre, and provided BG produce 350 to 450 lbs of forage annually the water will remain conducive to growing trophy LMB.

Thanks jpsdad, that's a lot to digest. I will get working on it.

In short, yes, you can do it over time. The overall impact on the predator fish population would be lessened, but still, there would be benefits.

Any kind of structure you can add that would help survival of the shiners would be good. Brush piles, Christmas trees, etc.

Thanks Sunil, there is quite a bit of weed and wood cover in the pond, but I had been planning on putting in some brush piles. I assume piles for Shiner fry would need to be shallow?

GB, there's some different talk about what niche areas of ponds Golden Shiners tend to hang out in. Some say deeper water, but I've seen them in all areas of the pond.

Yes, I would lean towards structure in less than 4' of water or so.

I was kind of hoping to avoid responding with culling recommendations but you pinned me down! LOL.

For sexing LMB, read this.

jpsdad, It's Ok, I'll just hold you completely responsible if it doesn't work out. Thanks for the link.

Sunil,


I really do appreciate your help and have been reading your posts on this forum for years. Would a satellite picture of the lake help? Or pictures of the current weed and wood cover? I have been reading up on GSH, currently pondering using a few of my livestock ponds to grow GSH to stock the lake.


Ken

Ken, we're always glad to help if we can!

I don't think it's necessary to post any pictures for the discussion, but we do love to see pictures.

I would just plan on stocking adult GSH in the late summers/fall, and doing GSH frye each spring. That way, you keep replenishing a component of the forage base, and increase the chances of establishing GSH in the lake.

Now, with the amount of $$/Gold Smoullions you're going to spend on GSH, you should think about what a feeding program might achieve for you. One strong benefit of feeding would be to get your bluegill larger. Much of all feed consumed by bluegill ends up in the LMB population one way or another. When the bluegill are 'amped up' on feed, conventional wisdom says they spawn more/better.

I used to be more of a purist when considering what fish species to stock and feeding programs. For example, I held off on HSB for a few years until my fish guy convinced to try them. I'll always have them in a pond going forward. Same thing for feed; once I realized what a feeding program could do, I would never go without it again. Now, having said that about HSB, I still would not stock a non-native fish like tilapia in one of my Pennsylvania ponds.

For the GSH Frye, you would need to get on Anderson Fish Farms list now or in the next few weeks to ensure that you'll get what you want come April/May 2024.

Ken, if you have other ponds you can use as grow-out ponds, I would grow bluegill, fatheads, and GSH in some of those ponds.

The harvest started this morning. My 82 year old neighbor and I caught a few, including a 18 inch at 4 lbs 3 oz. Kept a 16 and 14 incher. Early released a couple of other big ones.

Caught about 20 CNBG, RES and GSF. Biggest was about 4.5"

Nice!!!!

Who knew doing hard work to improve your pond could be so much fun?

Gunboss,

Good to see you getting started. You should probably get a good census of the LMB population. I was and still remain uncertain of the population of your initial stockers and recruits. In a young lake like yours the intial stocking can comprise a large proportion of the lake's LMB biomass and because of how good the fishing was for > 5 lb LMB I suspected (maybe incorrectly) that you had good survival of the initial stockers and that recruitment was muted. I ran several natural mortality assumptions (ranging from 15% to 30%) for the year class which yielded survival ranging from 7.23 LMB/ACRE to 19.08 LMB/ACRE. I leaned toward the 19 because you described fishing that was in the neighborhood of on 1 >5 lb LMB/hour and I know that's a remarkably good number for that size fish. Could, however, the mortality have been average (30%) where ~3.5 female fish per acre > 5lbs could provide that level of fishing? IOWs should I have used higher mortality instead?

The spreadsheet below depicts year by year growth of the initial stockers under the assumption of 15% natural mortality. We are presently at the end of year 5. One thing that gave me pause is the forage requirement of 662 lbs BG for just the initial stockers. Now with males half the weight as females that falls to 75% or 496 lb BG. With males undergoing more mortality than the girls that number could be reduced further into range that is doable for a very productive system. But if this were the case, it wouldn't leave much room for recruits which is something I was concerned about. What is the real number of survivors per acre? And what is the population of recruits? To be or not to be ... so to speak. If the survival was that good I am probably correct for suspecting very subdued recruitment. But the survival may not have been that good (and probably wasn't).



OTOH. With mortality average (30%) this makes room for somewhere in the neighborhood of 30 lbs/acre of recruits ... possibly up to 40 lbs/acre. In this later case, you don't have to harvest the >5 lb fish since they will be dropping off at around 1.5 to 2 per acre per year naturally. Whether you would harvest any of these large fish would depend on whether you think the harvest would increase total mortality or not. Some may argue that taking some would prevent some natural mortality (thus not affect the total mortality by much if any). For the most part, fish that large use most of their consumption to support metabolism and only a small part of the consumption actually grows the fish. This I think is why mortality averages 30% to begin with. LMB swiftly fill carrying capacity and so continued growth depends on mortality. This mortality is facilitated by the summer growth each year which grows the standing weight to a level where there is insufficient forage for maintainence. The strongest competitors are maintained but on average 30% die because they decline and become more susceptable to disease and other causes of natural mortality.

You expressed an interest in managing the water according to Richard Andersons PSD. Below is spreadsheet working with Willis' recommendation for the number >15" fish and Anderson's PSD recommendations for the other size classes in relation to the >15" population. I used the assumption of 30% mortality. Because of mortality, the <12" cannot be equal to the 12"-15" population (eg some of the < 12" will die of natural causes) but the population ratio for > 15" is very close including 30% average mortality. It estimates an annual harvest of 193 LMB in the 12-15" range leaving 2.34 LMB/AC (82 fish per year) to grow to trophy size. This should put you in place that is similar to where you are now. ~ 7 fish > 15" but where they are spread across multiple year classes as opposed to concentrated in the year class of initial stockers. The fishing should be similar to what you experience now but where ultimate weights and ultimate weights could be larger.



Caveats:

1. Only 82 fish per year should be allowed to grow from 12"-15" to > 15". These should be marked so they can be released when you catch them in the future.

2. The scenario depends on the recruitment of 16 LMB/ACRE into the 8"-12" class. If the recruitment to this size class is less ... then the harvest of 12"-15" must be reduced in order for sufficient recruitment into the >15" class. This is why I recommend marking trophy track recruits. OTOH, if recruitment into the 8"-12" class exceeds 16/Acre then some harvest of 8"-12" would be required.

3. If you are unable to mark 82 females in the 12"-15" class annually ... by this I mean that they just are not there to catch and mark ... then the >15" class may be under represented. This would be a case where recruitment is too subdued to maintain population numbers. This can occur where BG populations are dense and individuals are of smaller size. It tends to be less common on an ongoing basis but stocking a pond for trophy production is essentially setting the stage for this to happen in the early stages. If recruitment into the >15" size is underrepresented, then it will take more fishing effort to catch this class of fish but the ultimate weights achieved should be larger.

4. The scenario requires the production of 390 lbs of BG forage in the sizes the LMB need. This is in addition to the parental stock. To produce this much forage will require multiple spawns. If less forage is produced, the ultimate weight and growth will be reduced to balance the forage production.

Practical considerations:

1. The two size classes less than 15" in length consume 55% of the BG prey production. These populations could be reduced to allow more forage for >15" LMB. This would come at the expense of BG size. Given that BG are already small, this may indicate that the populations of less than 15" LMB are underrepresented.

2. The only way to be sure you have enough fish growing over >15" is to mark them and keep records.

3. The only way to be sure that you don't have too many fish >15" is to harvest unmarked fish >15"

4 The simulation assumes an instantaneous reduction by fishing of 12"-15" fish in the autumn each year. IOWs. These fish are allowed to grow all summer and thus are maintained and grown by in pond consumption which is the greatest of all size classes. To whatever extent some of this harvest mortality occurs before the end of the growing season ... less forage will be consumed by this year class and more forage will be available for all remaining fish > 12".

5. Supplementation of BG at the appropriate forage size could help maintain and boost forage production to the levels required. These should be stocked at around 3 inches in length if needed. In this size, they will benefit mostly > 15" LMB and to a much lesser degree 12"-15" LMB. Since 12"-15" consume in lake production at smaller sizes than >15" have much interest ... this is OK. They should get enough to eat provided they are not too numerous.