I am conducting an experiment this Winter to see how Gambusia will fare through a Central Ohio Winter. Two of the most common negative thoughts on the Gam's chances of making it through a cold Winter - 1) deprived of their ability to leap out of the water and escape hungry mouths, they will be eliminated by predation under ice cover, and 2) they will be killed by low temperatures - will be examined.

I have Gams in three different BOW this Winter, my 1/2 acre new pond (where 100 Gams stocked in June produced 100's of thousands to millions of offspring by Fall), my 1 acre established pond (where about 500 Gams transferred from the new pond during the Summer produced a smaller number of offspring, that nonetheless could be found in the shallows around the entire perimeter by Fall), and a 100 gallon horse trough (which had about 30 Gams put in it in early Fall).

These three locations have vastly differing levels of predation. In the new pond, the largest number of Gams face a small number of predators (a little over 300 total YP, SMB, RES, and BG, plus a lonely Walleye). The middlin' number of Gams in the big pond have a much bleaker outlook, being faced with well established populations of LMB, HSB, CC, BG, and RES. The 30 Gams in the horse trough have no predators to worry about at all.
Obviously, final results will not be known until Spring. I suspect the Gams in the big pond will likely be gone by then, but I think the species will still be present in the new Pond next year (is there any way 300-some small predators can eat what must be well over 1000 Gams apiece over the Winter?).

I do have some preliminary results on the question of Gams' cold-water survival abilities. We have had ice on the ponds for about 10 days now, and active Gams can be seen where the edge of the ice melts at the shoreline of the new pond on sunny afternoons. In addition, I forgot to plug the tank heater in the horse trough in one night this last week, and the Gams in it survived temperatures cold enough to put an inch of ice on the top and sides of the trough - the water temp must have been 32 degrees.

NOTE: These Gams, of a species not listed by the source, but described as "Winter hardy", are one of many species of Gambusia found throughout the country. Other species, native to southern climes, would undoubtedly have a harder time surviving in cold water.

Interesting experiement, Theo. I know your predator fish will feed during the winter, but you'd think the gams have a chance with the slower metabolism of the predators. That is, if they can survive the cold water.

They thrive in the shallows even in our hot South Texas summers. There's no telling what the water temps can be mid-day in 1' of water or less when the air temps are well over 100. They're hardy little guys.

Neat study. Info on the source would be good. It is not short term cold usually that kills the fish but extended time ( week +-) below there thermal limits. The limit is usually several degrees warmer than their lethal minimum. For example tilapia start the process of dying (cold ,stiff , lethargic swimming) about 5 degrees above their thermal minimum and stay that way for a week or so as the temp continues to drop. By the time they succumb the temp has reached the thermal minimum.

SRAC Tilapia

The intolerance of tilapia to low

temperatures is a serious constraint

for commercial culture in temperate

regions. The lower lethal temperature

for most species is 50 to 52o F

for a few days, but the Blue tilapia

tolerates temperatures to about

48o F.

Tilapia generally stop feeding when

water temperature falls below 63o F.

Disease-induced mortality after handling

seriously constrains sampling,

harvest and transport below 65o F.

Reproduction is best at water temperatures

higher than 80o F and does

not occur below 68o F. In subtropical

regions with a cool season, the number

of fry produced will decrease

when daily water temperature averages

less than 75o F.

Theo,

Back in the day we used to get ice thick enough to walk across the ponds at least once every year. Our southern gams survived well. I'm betting your more adapted subspecies won't have a problem at all. All bets are off if we have an unusually long string of days in the teens or lower.

Jones Fish

It always amazes me to see the prices that people get for those little guys.

I guess that makes me a millionaire.

Well you're sitting on a gold mine, Trebek!

IME they are only moderately hardy in cold temps. Some make it, most don't. But it really doesn't matter because before long you have hundreds again.

I haven't seen any Gams in the ponds during the brief periods they have been ice-free in the last month. But the Gams in the watering trough are still swimming around AOK.

Theo, How much daily variation of water temperature does the heated water trough have during days with temps in the single digits?

I've never had a thermometer on it, Bill, so I can't be certain. Normally "not frozen" is all the temp data we need.

When it's really cold, like the night before last, there will be some ice up on the rim of the water level. The heating element is probably working full blast to try and keep the water at "40 deg F" then. Other than times like that, is should stay fairly constant if the air temp is, say, between 15 and 40.

I did have it unplugged for a night (or two?) and it got 1"-2" of ice all around the sides and on the top. That was probably the most variation there has been this Winter (downward, anyway).

After a few days of warm temps and rain, the ice on my ponds was down to a very unsafe-looking thin layer, melted at the edges, yesterday. In the new pond (with the most Gams and the fewest predators), Gams were cavorting at the surface next to the ice. I saw 2 of them swim in 1/4" of water over the ice for a while.

Gams are a hearty bunch that is for sure. Their reproduction rate is off the charts, makes rabbits look like monks.

Oh and why no photos Mr. Moderator???

We have had almost 6 weeks of ice cover on the pond. After 2-3 warm days, it is thin at the edges. I saw 30-40 Gams active under thin ice in shallow water this afternoon.

Thanks for the update, Theo. Any news on the water trough gams?

I have not seen them at a glance for a couple of weeks (poor lighting at times I was at the barn). I strongly suspect they are OK, however.

I think you will be pleasantly surprised at how many pull through the winter, even under heavy predation... By July there will be so many in your pond you'll wonder if they ever stopped breeding during the winter!

Theo will probably retire selling them as "Northern Cold Tolerant Gambusia" Just think Theo, you could quit farming!!!!

You guys have me interested in these GAMS. Presently I have stocked my pond with golden shiners and fhm. I wonder if they would be a good addition to my S.Mich farm pond. I know that they are marketed as big time mosquito larvae eaters. I could over winter some of them in my greenhouse aquaponics system for the next year's brood stock. I also have a good sized drainage ditch that I was thinking of damming up for the propagation of some fatheads, and I could allow the gams to get started unmolested in there if the fhm and the gams would get along??

IME FHM will do okay with Gambusia in the same pond - IMO FHM numbers are somewhat lower than they would be without the Gams (prresumably due to egg predation).

Whether I would use them in a pond depends on what species I am going to manage it for. Gams are IMHO good for feeding small mouths (BG, YP), but I would probably not use then as initial forage if managing for large predators. GSH, for example, are a better choice there.


If I did really well at it financially, maybe I could afford to continue farming.


Live Gams sighted in the trough yesterday.

Theo:

They should pull thru the winter just fine. I had Jones deliver a dozen 2 years ago along with some other fish, and I put them in a 100 gal trough that I was using as a small pond by the house - no other fish in it.

I plugged in the heater just enough to keep the ice off of an area about 1' in diameter every other day during the winter last year (2007/2008) and they were still there in the spring. I upgraded to a 300 gallon one this winter, above ground level but surrounded with dirt, and have plans to run it down to the 100 gallon one this year (that'll be buried in the ground)via a man made "stream" and circulate the water back up with a koi pond pump/filter.

Remember, gambusia are native as fart north as central Illinois in the Midwest and Maryland on the east coast... They are pretty darn cold tolerant. They have done well for 20 plus years in a 2.5 acre pond in the mountains of central PA under heavy predation.

Michfish, you may be able to get them to overwinter in your pond without any special things being done. I realize central PA is not southern Michigan, but the weather isn't too far off.

I think gambusia give bass a good jump start in life. Often times when other species fry has outgrown the mouth size of young bass, there is a ready supply of gambusia babies ready and waiting to be eaten!

I have numerous sources of gambusia. If anyone wants to try some, if you are willing to pay the costs to ship a few your way when the weather warms I don't have any issue rounding some up for you... Just let me know!

They are hardy when it comes to transporting... Before 9/11 I remember catching some spotted gambusia (never seen one check this link http://www.aquabid.com/cgi-bin/auction/auction.cgi?fwlivebearersw&1234502416 )and putting them in a small tupperware container and flying them back with me from FL. They survived the flight just fine!

Thanks for the offer. I'll probably get back with you when the weather mellows a bit. It's 55 degrees and raining here today. Very strange. And I just finished building my ice shanty????
My surface water fed pond is far over its banks and is making me nervous. At least there is nowhere to overflow but on my own property. The drain is working but not as fast as it is coming in!! I planted 60 pounds of fhm last fall and I hope to see sings of them still being around. Are the gams really better at eating mosquito larvae than the other fish and minnows in my pond?

Probably not. Darn near every fish eats mosquito larvae when small.

Mosquitofish have upturned mouths that are designed for feeding on surface items such as mosquito larvae. How much better they are at it, probably not much. But they will definately survive heavy predation as compared to FHM which will be long ago eaten. Banded killifish have a similar mouth shape, are more predation telerant and grow to about 5". A few hatcheries sell them and I feel they are a great forage fish for ponds. They are often called bull minnows in the fish trade.

I've been following this topic with much interest,and would like to add more diversity in minnow species to the pond, because I might add SMB, or HSB this year.
I have GSH, & PS'S, and looking into adding central mudminnows.
It's probably too cold up here for gambusia with ice cover from Nov.thru April, but they appear to be very tough.

Any thoughts or opinions welcome.

It couldn't hurt to try stocking them and see if they would survive the heavy ice cover. I know of two ponds that stay cold enough to support trout year round that also have helthy mosquitofish populations... If you need a source when the weather breaks I can catch you a couple dozen and if you pay for the shipping I'll send them up your way... You could also treat them like tilapia. Stock them in the spring and let them multiply all summer. Then close to winter catch a couple dozen to keep indoors until the following spring to reseed your pond.

As I said above another options would be banded killifish also known as bull minnows. I know Zetts Fish Hatchery in WV sells them so if you cannot find a wild population to collect from that could be an option. They reach a maximum size of about 4-5 inches and do very well in ponds even under predation.

Bluntnose minnows are also an option. They are very closely related to FHM but in my experience are a fair amount more capable of maintaining numbers under predation. Particularly if given good cover to take refuge in. I would look into locating a wild source of them as they are native to the Adirondack region. Bill Cody has a lot of experience with them as well and maybe able to give you a source for hatchery reared ones. He just said he will be publishing an article on bluntnose minnows in an upcoming Pond Boss issue. He and I are in agreement that they are much better forage than FHM.

Another option is the spotfin shiner. The challenge here is finding a source. They are native to the Adirondack region as well so you may be able to find them in the wild to collect. Bill Cody seems to be an expert in them, so he may be able to chime in on a possible source and if they would be worth your effort...

Thanks CJ for the info, one concern I have is how tolerant are these different minnows to acid water. My PH usually runs between 5& 5.5.
The first year of my pond in 2006, I put in GSH & FHM only, the GSH have done great, but never saw the FHM again after the first year.
I have a chart of critical ph ranges of fish, and FHM range from 5.5 and up, GSH range from 4.5 and up.
Other minnows shown to be acid tolerant are mudminnow,creek chub,N.redbellied dace, alot of other minnows are not shown, like the gambusia, and killifish.

All opinions appreciated.

The FHM probably were all eaten in short order if there were any predatory fish in the pond. The pH may have played a roll in their demise as well. 5.0 to 5.5 is pretty acidic. I think their pH tolerance would be similar to the closely related bluntnose minnow.

From what I researched, pH tolerance for GHS is 4.6, bluntnose minnow 5.6 and spotfin shiner 6.4. I don't know the exact number but I know both mudminnow species are highly tolerant of low pH as well. It appears both the mosquitofish and banded killi are not tolerant of low pH. Finding forage for your low pH pond may be a trick. Both the white sucker and creek chubsucker are very tolerant to pH with 4.6 and 4.7 being their limits respectively.

The mudminnow species maybe one of your better bets...

CJ, I've been searching the internet for 2 hours and it does seem that the Gambusia, and killifish will not tolerate acidic water.
The mudminnow and creek chub look like the best options, and maybe the northern redbelly dace.
When I put the GSH and FHM in the first year there were no other fish stocked that year, so I think the acid water did the FHM in.
Thanks for the PM, info on adirondack lakes, I had not seen that one, so I'll read that tonight.

Creek chubs won't spawn in your pond but if you put enough in there, they'll at least be food for your fish. I think I recall seeing your pond was fed by piping water from your creek into the pond... Perhaps the creek chubs may attempt spawning in that area...

I think the northern redbellies may do OK. You could also consider liming your pond to bring the pH up. I know they do that with a lot of the ponds in VA that have been hurt by acid mine drainage...

I've been trapping fish in the stream for 3 years and the only species in there are brook trout, PS, and crayfish. Thats how I got PS's in the pond, it was a month before I put a filter box on the inlet hoses, but I wanted PS's in the pond anyway.
I would be afraid of introducing creek chubs to the stream because it might upset the trout reproduction.

The Adirondack Lakes survey has info on most of the thousands of ponds & lakes up here, and I found 5 listed near by that contain a different combination Mudminnow, Redbelly Dace, Banded Killifish,and Creek Chubs, so I'll be trapping this spring.

Putting lime in the pond probably wouldn't help for long with 40gal-min. flowing in. The DEC had better success reclaiming acid ponds by heavily liming the surrounding ground, but either way it's an expensive proposition.

CJ, I don't know if you have Pumpkinseeds down there, but if you ever need some let me know.

Fortunately PS are native to the Potomac River which is the drainage I live closest to. Some very pretty fish! Hopefully that survey will give you a good start in finding some extra forage species for your pond...

Posting a final Winter report.

The Gams made it through the Winter AOK in all three BOW - the new pond, 0.45 acre (no aeration yet) with a huge Gam population going in to Winter and a minimal number of newly stocked predators; the old pond, 0.9 acres (windmill aerator) with a middlin' number of Gams and well established populations of BG, RES, LMB, and CC; and the watering trough, 100 gallons (tank heater to keep it at 40 degrees or more), with nothing but horses trying to drink the water. Gams are present and active in all three, with a very large number apparent in the new pond.

Now I am anxious to see how the SMB and YP fingerlings stocked last Fall in the new pond do this year on GAM + FHM forage. I haven't caught anything in that pond yet in just a couple of attempts, but I did have a couple nibbles and lost worms yesterday.

Good to hear Theo, I was confident they would pull through in all your waters just fine. They are tougher than people think!

Interesting, I guess that opens up Gambusia as an option in my pond. I always thought they wouldn't make it through the winter in my pond.

Further north, I believe there is a substantial die off at times of gambusia due to the cold, but enough survive to repopulate the pond the following spring. As long as your get gambusia who are native to the northern natural range I think you will be fine.