Pond Boss Forums INTRO Questions & Observations What makes exceptional trophy lakes different?

I always wonder what makes lakes like Dixon Lake, CA and Lake Biwa, Japan different than others. Usually, when you read about those differences that make trophy lakes exceptional the explanation is a particular forage fish that flourishes there. To be sure, consumption of forage is essential to growth but I wanted to explore other possible factors that raise the bar for the best of the best when it comes to ultimate size of LMB. Both Dixon and Biwa have mixed Florida and Northern LMB genetics and both have produced LMB breaching 20 lbs. In the case of Dixon multiple fish greater than 20lbs have been caught to include the LMB fondly called Dottie which was last caught in 2006 at a weight exceeding 25 lbs. Dottie was foul hooked on her last appearance and so was not submitted for a record. In Dixon, forage is supplemented (unintentionally) by RBT stocking. We know that in both lakes the LMB are getting plenty to eat because they grow to 20+ lbs. So I wonder, what makes them different than other lakes that produce similar or larger amounts of forage yet are not able to produce such impressive fish.

Water quality is a potential factor and so I have investigated this as a potential contributor. One factor of water quality that interests me is temperature. I have recently formulated temperature dependent conversion parameters from the findings of the paper on LMB conversion of GAM that I referenced in the thread titled "LMB are remarkable converters of fish". There are two parameters affecting conversion. FCR (food conversion factor). One is Intrinsic FCR. This is the FCR of the consumption exceeding what the LMB needs for metabolism. So this is not Gross FCR. The other factor is Specific Maintenance Rate (SMR). The SMR is the weight of forage that is needed to maintain the weight of an LMB. It is weight of prey divided by weight of predator and it applies to all LMB regardless of their actual individual weight. As one might suspect, these parameters are temperature dependent and so using a single value for each is a rather blunt instrument. Applying the temperature dependency provides a richer understanding for the seasonal forage requirements for maintenance and growth. Depicted in the graphs below, the Intrinsic FCR improves with increasing temps (a lower number reflecting more efficient conversion) while the SMR increases with increasing temps. Higher SMR works against efficient conversion. So the two parameters work against the other with regard to temperature. Low SMR helps at low temps while High FCR hurts at low temp. The inverse applies to high temps.



It turns out that the temperature that is optimum for the most efficient conversion depends on the consumption above maintenance. Since growth is a function of consumption above maintenance, we can alternatively say that the optimum temperature is related to the rate of growth. By holding the growth rate constant we can divide the consumption rate required for the specific growth by the specific growth rate and the result is the Gross FCR (the FCR after the maintenance requirement has taken its share of the consumption). Assuming a fixed daily growth rate we can then calculate the Gross FCR across the spectrum of temperatures to find which temperature is most optimum. For a fish that is growing on any given day at an annualized rate of 20% the optimum temperature is predicted to be a frigid 39.2 F as depicted in the image below.



This finding wasn't something I had anticipated. But this daily consumption to support that growth is only very marginally above what is needed for maintenance and because what is needed for maintenance is so much less in frigid water ... the FCR of 20% annualized growth is optimum at that temperature. For BG prey ... the Gross FCR is 15 when growing 20% annualized at 39.2 F where it must consume 3/4 of 1% of its body weight daily. Big fish grow this slow or slower but smaller fish can grow much faster and if they are growing fast enough the optimum temperature will be higher than 39.2 F. At growth rates exceeding 90% annualized growth ... the optimum temperature increases. Obviously, a 10 lb LMB can't double its weight in a year and so we can come away with this insight. For fish growing at slower rates,(that is big fish), cooler water favors their growth over warmer water ... provided ... the same quantity of prey is available and consumed.

Working with daily average temperatures I found that I could construct formulas which model the average daily temperature as a function of the day of the year. I wanted to compare DFW (Dallas Fort Worth) with Dixon Lake (Escondido, CA) to see if there exists any advantage to Dixon Lake temperatures compared to DFW. The temperature profiles are depicted in the leftmost graph below. Note how the average temps in Escondido CA are much more moderate than DFW temps where the temps are much cooler in the summer and only modestly warmer in the winter. On the right side are Dixon and DFW SMR curves reflecting the differences imposed by temperature. It is clear that it takes more consumption to meet maintenance requirements in DFW than it does in Escondido.



One way to quantify the difference temperature makes is to constrain one location to maintenance consumption. Start each with the same weight of fish and then allow them to consume equal portions every day based on the maintenance consumption of DFW. Below is the comparison where Dixon LMB can gain 14% on DFW consumption that leads to no gain.



Now I will mention that the advantage is temporary without mortality. In other words, the temperature advantage actually only allows for an increase in carrying capacity. Once the standing weight in Escondido reaches carrying capacity... just like in DFW ... there is no growth. This can be demonstrated by simulating a second year where Dixon starts with a standing weight 14% higher than DFW. This result is depicted below where the Dixon standing weight finishes the year only marginally better. The effect year after year diminishes terminating at a 17% increase in carrying capacity. Alternatively on can calculate how much maintenance is required for the same standing weight of fish ... the result is ~17% less than in DFW. This demonstrates Swingle's principle that fish grow into maintenance and then stop growing (without mortality). To maintain the benefit of temperature in fish growth year after year requires balancing the benefit with mortality that is essentially equal. IOWs if Dixon has 14% greater mortality than DFW then the temperature benefit will be realized (evidenced in the growth rates of individuals).



So we can draw a couple of conclusions from this thus far. The temperature profile of Escondido, CA is favorable to the growth of large LMB AND the mortality of large LMB is also high enough to keep them growing throughout their lives. It makes sense that Dixon has high mortality of large LMB in that it is a trophy destination that gets a lot of fishing pressure. Per acre, more fishing man hours than most impoundments. This small (68 acre) BOW has nonetheless produced many trophy LMB. At Biwa Lake in Japan, it is illegal to release an LMB unharmed. They must be removed and killed. So the mortality in Biwa is probably much greater than in Dixon (as a % of biomass). Biwa is another favorable temperature profile for large LMB, with high mortality, and without the same benefit of supplemental trout forage.

I will also mention that both Biwa and Dixon have clear water. Clear water facilitates the use of deeper cooler water as temperature refuge for big fish by letting light penetrate and generate O2 production. Big fish use this water to lower their the metabolic requirement for consumption and to better convert what they consume to growth. Low clarity will tend to reduce a large LMB's ability to use cooler water because the O2 production below light penetration will cease.

Ok you remind me of one of my dental school professors; so what do I really need to know..................This is what I think I gather from all your confusing info....................Cooler clear water environments with a combination of northern and florida strain bass in the abundance of forage grow the biggest. Hows that.

And I think you are saying harvesting bass is a good thing??????

The legendary fisherman Murphy used to claim that many of these California lakes had large bass that had just become smart and almost uncatchable without using live bait techniques or light line and stealth presentations.

In-fisherman has shown some pretty interesting studies on how many times a bass can be caught in its lifetime and it's remarkably small the % a bass will be caught multiple times, so the idea of releasing a 5lber so that it can grow to 8lbs and then u can catch it again might not hold water so to speak.

In-fisherman has shown some pretty interesting studies on how many times a bass can be caught in its lifetime and it's remarkably small the % a bass will be caught multiple times, so the idea of releasing a 5lber so that it can grow to 8lbs and then u can catch it again might not hold water so to speak.

A 27-year mark-recapture study of largemouth bass caught and released in Wisconsin provides insight into how released bass fare.* A total of 1,054 bass averaging about 10 inches in length were landed using barbless hooks and briefly held in livewells prior to weighing, measurement, tagging, and release. Recaptures totaled 1,066 and occurred between one and 98 days after initial release. About 39 percent of all fish captured were never recaught, 20 percent were caught only once again, and 8 percent twice; but the remaining 27 percent were re-landed between 4 and 22 times. Near-adult largemouths weighing about a pound or more had significantly longer recapture intervals than juvenile bass, suggesting that bass learned angling-avoidance with age.

So if 27% of your bass are the ones you catch over and over again think about all the bass that never bite. This leads to people making false assumptions about lakes being fished out cause they can't catch any bass anymore, well yea all the dumb ones got removed.

Look into what happens in many of the CA lakes. Mild water temps ( temps stay in growth range for much of the year), stocked RT as a bonus. Also, maintenance is not a static figure. You have to account for energy used to catch food. In the CA lakes the RT are like pelleted fish food - easy to catch without much energy used. First the LMB know that when the stocking truck arrives it is time for them to corral the unhabituated RT at the stocking point and feast. Soon thereafter the remaining RT find themselves trapped in a small vertical area where the surface water temps are too high for them to be comfortable, and the thermocline is a bottom barrier. The LMB can go below the RT and above them and a feeding frenzy occurs. Easy picking for the LMB.

See California lakes link

https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=22664&page=1

Genetics, water quality and easy to catch groceries.

Very good topic for a post with informative and thoughtful discussion input. I like it. Harvesting bass using a type of slot limit allows more 'room' for or additional bass growth toward your goals. LMB weight density at the pond's carrying capacity slows the growth of bass.

Hmmm, I have two out of three of those items available to me.

Unsurprisingly, my RW is a little over 100.

Spicelanebass, I think everyone will take from the thread what they will and you are welcome to take this from it. To be sure, what you gather from it is true ... but it is probably something you already knew.

Everyone, will take something or nothing from it and that's OK too. Some will wonder things like, considering LMB covert better in cooler water, should I feed forage in the cool months to help them grow or prevent weight loss? (I have personally observed 9.5" LMB grow 3 fold in weight from mid-Sept to April). Another might question how deep his pond will be constructed and whether he would prevent his ponds potential for cool water refuge with aeration and/or fertilization. Another might say, "If I can know how much forage my fish need for maintenance and reasonable growth at different temps ... then I can know just how much forage to supplement at any given time and even know when I should expect it to run out. Everyone is different and I don't expect anyone to take anything particularly from it so all is good.

RBT are important to Dixon Lake. They contain on a wet weight basis ~45% more energy than BG. Very good food. I am not sure of the frequency of stocking but will monitor it through this season. Per their website, they stock 4000 lbs of trout at each stocking with the first stocking this year in late November. These are heavily fished for and humans take their share. At least some of the trout stocked are fish that are too big for a LMB of any size to be inclined to eat. Also this lake grows absolute monster CC. 47 lbs I think is the lake record. Trout probably play a role there as well. I am sure there are a lot of trout morts that are consumed by LMB and CC alike. At 4000 lbs per stocking the stocking rate is a little under 60 lbs per acre. What percentage of that weight is small enough to eat and what percentage is left by anglers ... I do not know. But I do know there is a limit to how much an LMB will eat on any given day. An LMB >10 lbs doesn't eat a lot above its maintenance needs (which is why they grow slow eg <25% annually) and so now with water in the 59 degree range they need about 1% of their energy content for maintenance each day. Of RBT, they need .69% of their body weight for maintenance. So consider a 10 lb LMB eating a 10" stocker trout. That RBT contains 5 times what a 10 lb LMB needs for maintenance that day. The Gross FCR at 59F is 8.4 and it would gain .43% from that consumption. Doesn't seem like a big number ... but ... it is 379% annualized growth. Yes, that is correct. We know Dixon lake 10 lb LMB don't grow to 47.8 lbs in a year and so consumption at 1 trout a day is not even remotely possible. It doesn't take many trout to make a difference for Dixon Lake Trophy LMB. One every 3 or 4 days is enough to grow them remarkably. There may even be enough RBT mortality from natural causes to supply that consumption through the cool months where they could just pick them off bottom not even having to chase them down.

Even so, what about summer? How long do the trout last? RBT are important but I suspect despite the low fertility of Dixon Lake there is sufficient BG spawning to maintain or at least slow down warm weather decline. Cool deep refuge also helps to slow decline.

The lake has some very remarkable fish in it. For any interested in checking out some of the fish caught there ... here is a website with photos.

This is the lake record CC.

As an update. RBT live in Dixon Lake year round. I was thinking they were stocking the massive fish shown in pics but in August a ranger discusses how even though they had stopped stocking in March that people were catching RBT. He mentions that the normal size of RBT is between 2 and 5s with an occasional 8 lb plus. The Lake Record for RBT is between 16 and 17 lbs.

I also saw a striped bass photo. It weighed 22 lbs but was very lean so summer forage must not be as abundant for their preferences. They may also be more gape limited than LMB as the RBT grow.

Check out the photos. BG > 1.5 lbs are caught. >2 lb Crappie are also caught. Just about everything can get big there.

At 60 lbs/Acre/stocking ... A schedule of every two weeks through March (when they stop) could be as many as 9 stockings or 540 lbs of RBT per acre-year. Most of RBT that are consumed, I suspect, are consumed by >10 lb LMB. A 20" LMB could swallow one at stocking but catching one would probably be limited to when new stocking occurs and the occasional mort or soon to be dying fish. Any trout consumed are a boon to the consumer. Hatchery strains of RBT can grow at 1 inch per month and the .36 lb RBT they would stock in December could be 18" and two pounds (standard wgt) by the following August. So the prevalence of August caught trout >2 lbs is in line with that. December stocked RBT are very close to immune from predation by April for even the largest LMB. In the examples, I am assuming 10" average length for the stockers but 12" stockers change the outcome to favor LMB that have managed to grow very, very, large. A smaller stocking size of 8" would bring many more LMB into the trout consumption loop.

What weight of trout consumed by LMB would depend on a few things. First, the weight of LMB consuming RBT. Second, the rate of consumption. Third, the rate of growth of the trout forage. And finally the consumption of forage sized trout by competitors like humans and CC.

Spicelane, Another influence is the rate of consumption by large bass. They consume more infrequently than smaller LMB which have higher rates of growth. In the presence of large consumable prey like RBT which are very energy dense, a Large LMB need only eat once every 3 or 4 days to grow at <25% per annum (a 25% growth rate is very, very high for >10 lb LMB). If a LMB is only eating every 3 or 4 days and if it is pretty easy to consume prey ... most of the time they are couch potatoes and not interested in eating anything.

Eric, you may be underestimating the metabolic requirements between consuming prey. They are there too and unless it is very, very, difficult to capture prey the energy savings of easy consumption may be less than we tend to give it credit. When I apply energetics and the dry weights of wet forage ... I am seeing that wet fish conversion is on par with feed for equivalent digestible energy consumed. One of the key differences, however, is that it is possible to consume more digestible energy with feed because it is fed in a dry state. Consumers have to negotiate the water content of wet fish and this diminishes how much energy they can consume of wet fish relative to feed. Improvements of conversion, apparently, come only from the increased consumption of energy ... particularly that portion that exceeds energy required of metabolism. Although metabolic demands for energy increase with increasing consumption ... this is apparently only partially related to the predation expenditure of energy. Just the digestion and assimilation of nutrients require energy as it is not 100% efficient.

I whole heartedly agree that supplementing forage is like feeding a pelleted feed. In the case of typical LMB ponds, unless one is feeding formulated feed directly to the LMB it is much better than feeding the BG to feed the LMB. Fish comprise a very minor part of pond nutrients being several layers removed from primary production. If one can afford to produce forage outside the fishing pond in a forage pond then adding the forage is approximately the same as adding their dry weight of a 67% protein feed comprised solely of fish meal. To grow the same weight of forage using the natural chain of the fishing lake requires a commitment to nutrient mobilization far in excess of that comprised in the forage supplement. In a forage pond, one can grow forage in hyper-eutrophic condition at high density and then put of fraction of the nutrients required to grow them into the fishing pond. Forage introductions make possible predator standing weights much greater than the trophic status of the fishing lake would otherwise support. Dixon Lake is a very good example of that strategy where the clarity most of the time exceeds 3 meters (9.8ft+ = low natural productivity close to oligotrophic). Cody note- how many ponds or small lakes with have this clarity and the sizes of trophy fish as Dixon??

I looked up some stuff on Lake Dixon and found that August water temps down to 15 feet were at 82.9 degrees above the lethal threshold for trout. I have no idea if Lake Dixon stratifies but it must have O2 at deeper depths to support those trout. I also saw where CDFW were stocking 33,000 pounds of trout into Lake Dixon per year, keep in mind Lake Dixon is only 70 acres. That's a lot of cash which most of us just don't have the means to do.

I see you are from Texas can you explain why OH Ivie is kicking out so many huge fish??? Anything unusual going on in that lake we would be interested in hearing about????

Wow Lake Dixon even intentionally stock thousands of pounds of channel catfish, and the lake has zebra mussels, two things many experts would say would inhibit the presence of giant bass............

What is OH Ivie?

Bill, a Texas lake. Probably at least 30 years old. Highly managed by TPWD.I haven’t fished it in many years so don’t know about it these days..

Spicelane, would you post the reference (web address) stating the 15 foot temperatures? I would like to relate that to the average daily temps of the year. My suspicion is that it was a year of above average temperature. Average daily air temperature for Escondido in July and August is around 76 F, and so in most years the lake could support trout provided the water at and below the thermocline receives sunlight. Above average temps could prohibit survival and this may have happened this year.

Your post caused me to look at more reports. Doesn't look like they are always current. For example, on 09/11/23 they report:


The buoy line is the off-limits line around the dam. It crosses the some of deepest portions of the lake.

However on 09/28/23, just 3 weeks later, they report:


Spicelane, OH Ivie has times of draw down. Right now its 28% full according to an online article. Drawdowns reduce standing weights and when refilling takes place there is a lot of forage produced relative to the predator population. That probably contributes to it. South Texas ponds are very productive for large LMB for the same reason. The effect is not limited to Texas. But in Texas, especially where OH Ivie is located, rain comes in fits and starts.

Spicelane, CDFW isn't actually stocking forage. It isn't the intention to feed LMB but rather to provide RBT fishing opportunity to fishermen. The fish are too big except for a very small segment of the LMB population. Some of the weight stocked is just too big to eat like the 2 to 8 pounders. Fishermen remove most of the fish anyway. There is no catch and release of trout there. Anyone stocking like CDFW to feed their LMB would be paying the stupid tax.

Trout are an excellent winter and spring forage that is affordable for most to do. The way to do it properly is to stock small RBT. Overton's here doesn't handle them any more and I can't remember if they were 4" to 6" or 6" to 8". But a year or two ago they could be bought for $16/lb. The appropriate stocking rate is a weight where the loss of weight of predation is replaced by normal weight gain. So you start with a given weight and the standing weight of the RBT slowly grows as they grow and LMB consume them. The consumption is limited and predictable. At the end of the season you still have a similar weight of RBT ranging in sizes from 9" to 13" but the LMB have consumed several times the starting weight of the stocking. The cost including feed for the consumed forage is < $4 lb and if you want ... at the start of April ... you can harvest the larger RBT for your own consumption.

A lot of those RT are expensive LMB food. Several of us years ago checked on the CA events. ...from Doug Hannon, who is widely regarded to be one of the premier authorities on largemouth bass.

This in regards to California largemouth that reach twenty pounds:

"The balloon-like proportions of these fish indicate adaptive specialization at its extreme limits. Just as coyotes have adjusted to susbist on garbage and poodles in the Los Angeles suburbs, California bass have adjusted to feed on stocker rainbows. Staying close to this food source, which has a preferred temperature around 54 degrees F., keeps these bass in the cooler fringes of their environment, which in turn triggers the fat-storing mechanisms of a pre-winter metabolism. As a result, an 18-pound California largemouth is no longer than a 10-pound Tennessee bass, just a heck of a lot fatter". Tracked down several of the state guys who did the transport and stocking. They described the stocking as mostly 1-2 lb. fish, which were upon release immediately ambushed by LMB. With no habitation they guessed that predation was 25% in the first few hours after release.

I do agree that stocking RT in ponds can be a good idea.

Would be nice if Texas would stock 1 to 2 pound RBT! Here in Texas it is generally 8" to 10". The LMB in Dixon must be the reason they are stocking trout so large. To help with survival. I've no doubt they guessed 25% but it still seems like a large number to me if for no other reason because of the number of LMB that would be required and the average size required. Not being exposed to predation they are thrown into a situation where the LMB know what to do and they don't ... so they are definitely more vulnerable in the first few hours. Even so I doubt the RBT just give up without trying to get a way and I would bet the 180 RW lunkers are no faster than 14" to 18" RBT ... so I would bet that the LMB focus on the smaller 14" trout of the stocking. If the CFDW were challenged to demonstrate that trout stocked weren't being wasted with 25% gone in a few hours and presumably the lion's share of the rest in a few days ... I would bet that they could justify that losses were muted and that most RBT are being recovered by fishermen. One of the ways they could do this is to explain that they go to a lot of extra expense to grow the trout big and they could demonstrate with science that bass are only taking a small percentage of the stockings because only a minority of the bass in Dixon are large enough to consume them.

Consider the table below. Generally 50% the length of the LMB is considered a practical limit for consumption of fusiform prey. Its not that they cannot swallow modestly longer prey ... but to be successful at capturing prey the length of fusiform prey is usually under 50% the LMB's length. When 50% prey is consumed they may be dead already, in the process of dying, or just incredibly unlucky. It happens but it is not very frequent. Given that the trout are not habituated, let's a assume the LMB are consuming live and vigorous RBT up to 60% of the LMB's length. For the minimum sized 1 lb stocker (14"), this requires a minimum length LMB of 23.3" and at 180 RW we are talking 14 lbs. This is the minimum sized LMB needed to consume the smallest of the trout stocked. A four thousand pound stocking averaging 1.5 lbs fish will have in the neighborhood of 2666 RBT and if 1/4 are 1 lbers, then the standing weight of >14 lb LMB would have to exceed 137 lbs per acre ... that is ... if none of them were heavier than 14 lbs.

So maybe they eat more than one RBT for each LMB in the first few hours. To test that theory I computed % of body weight of the consumption. It just doesn't make sense that a 23.3 " LMB would consume 13.4% of its body weight twice in one day. If it managed to consume one, I truly think it would stop eating for a while. Even adjusting for 180 RW 7.44% seems much too high to consume a second RBT which would likely have to be larger than the first. Now I am not saying that 25% are not consumed but if those guys are correct then it requires a huge standing weight of >14 lb LMB. If it takes a 23.3" LMB to consume a 14" RBT then one must ask the question. How do LMB in Dixon get to 23.3" in first place? It can't be the trout ... they must be eating other things. So the natural food chain would have to grow them to 23". I doubt that in this lake that enough 23.3" LMB are produced by the natural food chain to balance the trout consumption they figured. Also keep in mind that trout die of stress naturally over a two week period after stocking. These and those taken on the day of stocking should be sufficient grow > 14 lb LMB of a more modest standing weight quite remarkably.

I can shed some light on the LMB and the trout in Dixon that you cannot learn from reading a book or looking at articles. First hand knowledge as in been there fishing and lived relatively close for 10 years. Close as in 20 - 25 minutes and 19 miles away.....

Don't believe everything you read is the first thing.

Dixon is a hair bigger than 600 surface acres, and they stock 3,000-4,000 pounds of trout per stocking. While that doesn't feed ALL the bass in the lake, when they do stock them the LMB that are in that particular area know that the feed bell is ringing.

The trout are stupid and sometimes in shock when stocked. The trout that are stocked are mostly 10"-16" and I have NEVER seen a 2# trout stocked unless the CDFW stock some of their large brood fish after they have spawned and they need to rotate some inventory. That's how you see the 10#-12# trout caught. They didn't grow that big there in Dixon.

The CDFW can't temper the fish there. They take a good educated reading as to the water temp there when they leave the hatchery and dump the fish in. BUT water temp can fluctuate depending on the sun/clouds. Sometimes it takes a while for the trout to get acclimated sometimes not. BUT, I have seen trout just swimming and a LMB just swim up to them and suck them down. Trout that have absolutely no idea what a predator is doesn't have to be eaten by a bass that swims faster than it does; they don't think that they can get eaten and when they get sucked in, it's too late. Depending on where they are sourced, they could have been on the trout truck for 12 hours. That will slow them down too.

Trout are only stocked in the winter, the rest of the year the bass have a great population of Bluegills and to eat.

The LMB get habituated to the trout stocking trucks and it's a blood bath when the trout are stocked. There is a reason why the large trout imitation swim baits originated in Ca.....

The water there is CLEAR, so visibility is really, really good. If the lake hasn't gotten any runoff from a rainstorm, you can see 10+ feet visibility.