Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Fall RBT for LMB Stocking

Digging into RBT a little bit for 1st year LMB. Max of 50 LMB (assuming that all are still alive and no mortality over the coming winter) in the pond currently and thinking we might bring in RBT as winter forage.

Have only sampled (1) LMB at this point and will likely sample a few more in Sept/Oct. Of the single LMB we sampled it was 155mm (6.1") 79g (.174lbs), running 158%RW (PHat Toad). I don't know if the one we have measurements on is a runt, avg or jumper...
Pond is 1.5 acres, Forage stocking was 35:1.

Is there a realistic number of RBT for a small BoW like this with just a few LMB present?
My understanding from the Hatchery (Crystal Lake) is that 4-8" RBT would be available in Late Oct / Early Nov. By then if said Phat Toad LMB continues at current pace it should be in the range of 10-11" (avg of 1.62mm per day)

I suspect in coming years this number might change as there will be additional mouths to feed. This first year however we have an extremely low numbers of mouths.

Very awesome growth Boondoggle. Could be a jumper but may also be average. Here, I am seeing average growth to 6" by late September. These don't have the minnow abundance that your new pond has and so growth is slower. By late September you might catch the same fish at 8 to 10".

The RW is near the limit especially for a yearling LMB. They grow in length so fast that it is harder for them usually to pack on that much excess weight. But again, low competition and abundant forage makes a profound difference.

So I guess what I am saying is that forage availability isn't a problem for them yet. But lets say you have 50 LMB averaging 9" and 160 RW in late September. The standing weight for LMB will be 26.3 lbs. To maintain that weight through an average Tulsa winter ... they would need to consume 30 lbs of GSH or 36 lbs of BG. If they consume more ... they will grow.

You may recall that I grew 9" LMB to >13" over a winter (Bill, this was Northern OK, 20 miles south of Kansas ... not DFW). When I run through the simulation for Green Sunfish ... LMB were consuming 4 times their daily maintenance needs throughout the period. Daily maintenance over the six months starting 10/1 through 4/1 ranges between 0.5% to 1.5% of body weight daily. It depends on the size of prey how many are consumed but during the warmer months of the period at 4 times the daily maintenance ... for prey 1/5 their length ... they needed to consume 6/day in the warmer periods and as little as 2 per day under ice. It is possible that consumption was less during coldest days and more on the warmer (as opposed to constant excess consumption throughout). It is also possible that the opposite is true. They may have exceeded the constant consumption on the coldest days. One thing I can tell you is that for the same proportion of consumption over maintenance, the Gross FCR is BEST on the very coldest of days. So ... if the latter where proportional excess consumption is greatest on the coldest days ... there would be substantially improved Gross FCR on those days.

You have more LMB (50 compared to 10 in my anecdote) and it will take more forage to accomplish the same growth. When I run the simulation on BG the requirement to match length increment at the same RW (160) the amount of forage required is large. For BG, the forage they would need to consume is (299) lbs of BG. Now in your 1.5 acre BOW you may not have forage to support (200) lbs/acre of forage consumption to carry them through the winter with this level of growth. If you did, you could have 13" fish averaging 1.75 lbs each. Of course with mortality, the forage consumption is less, just tongue in cheek assuming 50 LMB.

Back to your original question ... I would not recommend RBT for forage. The problem is they are too large for the yearling LMB. On the other hand, RBT can grow 1" per month and you could have a crop for fishing stocked at those lengths by late March and April. Just for fun. 4" to 6" will be ideal forage for >18" LMB. For forage, wait until the LMB are exceeding 18" in length.

If you want to maximize growth over winter, you will probably have to supplement forage this fall. Sure, a shooter or two might make the maximum but they just out-competed their competition for a limited resource. To get maximum individual growth from all, you will have take the competition factor out. IOWs, prey must so abundant that competition plays no role for the amount of forage consumed. Under these conditions, there will be less variation of growth and all fish will grow at their individual maximum potential. I like GSH as supplement forage. It is affordable and will never not be forage (will always be consumable). For 50 LMB consumption needs to be 250 lbs of GSH. GSH will grow a little through winter gaining weight and so you can stock a lesser weight than that. I would stock GSH ~ 2-3" in length expecting growth to a maximum length of 4" by April for the larger GSH stocked. If all they had to eat was the GSH you would need 145 lbs of GSH on Oct 1. The amount to stock depends on survival of your LMB stocking and how much forage is available in the pond on Oct 1. Multiply survival to that number and subtract your estimate of the standing weight of consumable prey. If you supplement 145 lbs of GSH there will be better survival (along with more survival of existing prey) on April 1st.

Now there is one more thing to consider. Lets just say you did it and lets say it's a rousing success where fish are averaging 13" and 1.75 lbs each. If 35 LMB have survived, then you have about 22 LMB to the acre weighing 41 lbs to the acre. This is a fairly large percentage of your LMB carrying capacity, you will need mortality at least by the third year to keep them growing well (definitely needed for maximum growth). If you can remove some males before they spawn next spring this would help by reducing recruitment and competition for forage. 13" LMB will benefit from tilapia next year.

Thanks JPS. I'm always impressed with the calculations and amazed at the forage base required to grow LMB. I will say very little of the growth these guys are showing is on me. My job was to get the pond dug, put in some habitat, rain dance to get it filled, add in some fish and now monitor to ensure they have what they need. So far, the fish seem to be responding well. I think this goes to the old saying you can lead the horse to water but you can't make him drink.

My current plan is to start with a fish trap or two first week of Sept. Perhaps a little fishing as well to see if I can find a few more LMB so the sample size is greater than one. What I'm hoping to see with the traps:
1) Number of spawns we had this year on the BG or relative abundance of a particular size. We did catch a few and from what I can see the fish that are close to the feeder are near the same RW growth rate as the LMB and the ones that are further away are closer to 100% on RW. Of the six we caught, they ranged from 130mm to 175mm.
2) I haven't seen many of the GSH that we stocked or recruitment from them. Very possible it happened on the GSH and my rookie eyes just aren't able to tell the difference between GSH and FHM before the GSH head out to the open water. The minnows, generically, that we see along the shoreline range from 1/4 - 2". Starting to see a little mix of 2"+ more disk shaped intermixed with these guys. Unknown if these guys are sunfish or the tilapia.
3) Maybe we will see some representation from the YP as well. I didn't see any ribbons this year but the water was still very stained until their spawning temps/window had passed.

Is there something else I should be looking for here?

Picked the start of Sept as the temps should be starting to cool and to make sure we had time to try to get on a schedule for some sort of supplemental forage. Basically, our trapping should tell us we're missing something we want and then either fill that hole if missing or bonus forage with GSH?

Will definitely keep my eye out for the males. I'm not skilled in the use of catheters which will mean we run with what we have until next spring if we can catch some nest building or some egg laden females visually.

Will plan to hold off on RBT until we get a little more size on the LMB.

Much appreciated on the help and response!

Very good growth for the sample you have taken. There is a lot of forage and it may be helpful to use minnows for bait to take samples in September.

Just love the fact that your will be trapping to sample forage. In a conversation with another member, we discussed the need for standardized traps and procedures to estimate forage populations. I have read research for estimating GAM populations. They related trap rates to known concentrations and these proved to be effective predictors of populations with an acceptable range of error. Perhaps something can be done with BG, GSH and such but I have not seen any research on these species. Keep good records of counts, size ranges, and soak times.

The mentioned present size of prey is perfect for the LMB you sampled. As a general rule of thumb, LMB are able to easily consume prey less 2% of their body weight. As prey grows larger in weight proportion, it becomes increasingly more difficult to capture ... not to swallow so much ... but to chase down and subdue. More than 84% of the prey that LMB consume will be below 2% of their own body weight. Larger prey happens the rest of the time and it is not unimportant but the lions share (more than 70% by weight) will be derived from prey less than 2% of the LMB's body weight. Prey smaller than 1% of body weight doesn't stand much chance of escaping an LMB. They are easy meals. For forage supplement, an average weight of between 0.5% and 1% of the targeted LMB body weight is probably ideal because this allows growth through the vulnerable window of relative sizes. The key is stocking sufficient weight of forage that enough survive to grow through the vulnerable sizes. This will maximize the ratio of consumption over starting forage weight. If few grow past the vulnerable sizes, this is also good. That increases carry capacity available to vulnerable forage.

Boondoggle,

Do not cath to determine sex. That's fine if you absolutely cannot have a mistake ... but ... you have a mixed sex pond already. Doesn't have to be a perfect method ... just highly effective and not commonly wrong. Use the broom straw method. It can be done in the field without anesthesia and it isn't often wrong. There is no risk of breaking a catheter and very little risk to the tested LMB. Works best for LMB between 12 and 15 inches.

I totally got spoiled here. First cast at the pond off the lily netted the LMB bite. There are multiple spots on the pond to find them with the habitat placements, but definitely felt spoiled to find a LMB on the first cast. They will probably make me work a little harder for it in the future.