Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations What to do about HBG reproduction.

Hi,

My question is what fish should I restock with to help control the GSF/HBG?

This is the background to help answer the question. I've posted here before, but my parents have a .4ac pond that was originally stocked with HBG and perch. The fatal flaw was that a true predator wasn't planted. That is all it had for several years. It worked for awhile but eventually the HBG started reproducing at a high rate. GSF were never intentionally planted. What I'm calling GSF are the offspring of what ever ending up reproducing in our pond. Both the perch and the HBG offspring got smaller. At this point they asked what to do and I said that they needed a better predator then the perch. My mom wanted to keep as many perch as she could, so to me that ruled out LMB but thought SMB could be tried. SMB would be less likely to reproduce and would leave the larger YP alone. If SMB doesn't work out LMB can always be added later on.

So 33 5" SMB were planted a little over a year ago. Their growth has been excellent and seem very healthy. Since the SMB have been introduced it seems the perch population has gone down and the GSF/HBG numbers have gone up. That is even with using several minnow traps to get as many GSF/HBG offspring minnows as possible. Since the SMB have only been in the pond a year I don't think they've gotten big enough to put a dent in the GSF/HBG offspring. Since they seem to be preferring eating the YP, I'm guessing the YP were doing a pretty good job of HBG reproduction control. I haven't measured the SMB because I want to release them ASAP, but they seem to be around 9"

So I think the options are:
1) Stock HBG as this hasn't been done in 3 years. Everyone likes catching them and the GSF/HBG offspring aren't big enough to eat. The goal it to eventually get the GSF/HBG offspring under control and just stock HBG as necessary. However this seems to be the problem species so I don't know if it's good idea to add more fish to the natural reproduction problem.

2) Stock even more 5-7" yellow perch as they will eat the GSF/HBG offspring, plus the offspring provide the food for the SMB.

3) Stock more SMB since they don't seem to be skinny. (Only available in the fall and very difficult for me to get) Pond bottom is mud, no gravel for spawning beds.

I'm interested in everyone's opinion on my best option.

Thanks

Very interesting situation..
HBG usually produce nearly all male offspring, depending on the breed so I'm going to say your GSF were there in numbers before the HBG.
GSF will cross with any sunfish present which still leads to a high percentage of males, but I can see in your case, this is going to be very complex.
SMB are going to work on the most abundant forage in the size they prefer to eat which may not be optimal for control.
As for any sunfish present, I'd be pulling them out as you catch them. There's way too many present and the reason they are getting smaller. You say "perch" so I'm going to assume Yellow perch. 5-7" perch will eat smaller fish but the GSF are more likely to wipe out any YP production just due to there aggressive nature.
I really think you need to be keeping every sunfish you catch to help the situation, and even fish more aggressively for them.
I wouldn't stock any BG/HBG at this point, I believe it would only make the problem worse.
Maybe stock some HSB for some further control of small fish as the HSB can be controlled later without issues.
I'd leave LMB out of the equation for now, as that could be an additional problem later on.

Thanks Snipe,

Just to add some more info. In Wisconsin it's against the law to plant non-native species so HSB are a no go. The pond was dug with no possibility to gain entry besides planting. We use minnow traps, and keep all small GSF/HBG offspring. The planted HBG are planted at 5-7" so I can easily ID if it was planted or reproduced. So either GSF were accidently included in a HBG stocking. Or they are the offspring from HBG. What I'm calling GSF are not 100% GSF, they are the offspring from the HBG that didn't have very good predators for several years. My understanding is that without predators, given enough time, HBG will eventually reproduce with each generation showing more GSF traits.

I know that HBG reproduction can be touchy subject. However I would like to concentrate the replies on the next steps and not on HBG reproduction. If anyone wants me to start a separate thread I'll help in anyway I can including pictures.

The issue is that GSF are a part of the parent stock and although this is a touchy subject for some, they revert back to parent stock, hence the GSF, but you will still have some HBG reproduction. You have parent stock reverting back both ways so you will have some naturally occurring hybrids.
If HSB are not an option, to get things back in check, which you will need to do, you'll need a predator that you have some control over. My first choices would be nil to minimal reproduction possibilities.
#2 in my book in this case would be Walleye.
Until you take management action, you're going to have more and more GSF and smaller fish just because they are so prolific and aggressive.
If that's not attractive, do the LMB and be prepared for other management practices as they progress.
Another option is drain, nuke and start over.
To come back to this, you're going to need a large gape predator to do much good, control-wise. Maybe even northern Pike. Something capable of cleaning house, you just have to monitor closely and be prepared to implement whatever management practice is needed to get it where you want it to be.
Many predators can be used as a "tool" to fix a certain situation but once added you have an additional element that requires attention at some point.
I'm still not completely clear on what you want as an end goal, and I feel like I need to add that understanding the characteristics of the species present is part of understand how best to control them.

What I've observed in ponds around here which are stocked with HBG is that the GSF traits in F"x" offspring dominate the BG traits. I don't know if the majority of the offspring are born with GSF traits or if those born with more GSF traits are outcompeting the others, but the ponds I've seen end up with a population of sunfish almost totally comprised of GSF. I would assume similar based on your location being similar, but I don't know.

LMB or NP would be the best predator fish for managing the population, but both come with their own headaches (especially where your YP are concerned).

Predicting the numbers game is always hard no matter the species. Experience is a good teacher. Give your plan time to work and gather data to make decisions.


The degradation of subsequent generations of crosses is called outbreeding depression. They do not revert genetically to the parent species but evolve to Fx crosses. They may look more like one than the other parent but that is only a small part of what is going on genetically. Part of the suspected variance in data on HBG is due to the probable non-pure GSF parentage % .


I have not seen any reports/data on whether YP can control Fx HBG reproduction but it may be possible. I do not think the HBG can sustain long term as the forage base for both YP and SMB - they don't reproduce enough. If you don't mind mixed populations and want to try the numbers game you could think about adding a few BG adults to skew the HBG/GSF parentage %. This would lead to more offspring.

I’m in the same predicament. Stocked SMB, YP, RES, GS, and FHM (along with some HSB that have never been seen). Then I thought I’d stock some HBG for something easy for the grandkids to catch. I had the impression that reproduction wouldn’t be a problem due to the 90% male offspring etc..
My HBG have crossed with the RES and gone on from there. We do almost always have something to catch, but I prefer YP, and I think those numbers have decreased both from HBG and big GS feeding on the young YP. I’m not returning any HBG or GS caught. Maybe we will correct it so that the YP come back, but I’m not optimistic. My SMB are doing very well, but they can’t tackle the larger HBG. I may end up trying to find single sex LMB, but my chances of pulling that off are not good. In the meantime I’ll keep removing all the HBG I can. Good luck Sisu. I hope you get them under control.
I also added another fish trap to use this spring. Hoping to remove additional HBG.
Jeff

I also forgot to include an important fact, we also stocked FHM. (I was concerned with getting the SMB off to a good start) So obviously the SMB concentrated on the slow and dumb FHM and a big YP hatch.

I talked to a local fisheries biologist and I decided to stock more HBG. The thought is they will be 90% male so shouldn't contribute to the reproduction problem, but will eat any of the Fx HBG offspring.

Thanks for the help everyone.