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Breeding setup for gambusia?


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#1 Guest_jase_*

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Posted 10 March 2008 - 09:31 PM

Howdy,

I have roughly 30 Gambusia (holbrooki, I think) in a 29-gallon aquarium with some java moss and a big mass of yarn breeding mops as hiding places. I'm hoping to raise them as feeders, but I've had them for about 6 1/2 months now, and have yet to see a single fry, even though there always seem to be gravid females. After a couple days of post-shipping acclimation last August, I haven't had a single one die until the first male died this past weekend -- so I assume the setup is at least keeping them relatively healthy. I'm feeding them a mix of flake food and live blackworms.

I see from comments in http://forum.nanfa.o...?showtopic=2275 that gravid females can delay birth if conditions aren't ideal. Does anyone know how long they could delay for? Can they abort/reabsorb the fry and never actually give birth? I moved two gravid females which looked like they were about to drop into a separate 20g tank with breeding mops about 20 days ago, and still no change in their conditions.

Second, any evidence that it's common for Gambusia to demonstrate hermaphroditism (spontaneous sex change)? I see a few references to it in web searches, but no clear answers on how common it is. When I got these fish (sent from Georgia), I'm pretty sure I only had 3 living males. Now roughly 1/2 of the total are males. I could have screwed up sexing them when I got them, but I doubt I screwed up by that much. The alternative is that they really are producing babies and I'm not noticing it until they grow up (very possible, but still confuses me). At least now I have an accurate count so I'll know for sure if more start showing up.

Finally, the real question: Can folks give me tips on how best to set up for mass-production of these guys in an aquarium? I'd definitely like to avoid the hassle of moving females individually into breeding traps like the guppy folk do. Is it possible to add enough java moss or other hiding options that a significant amount of the fry will survive?

Thanks, Jase

#2 Guest_Irate Mormon_*

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Posted 10 March 2008 - 09:49 PM

I can't imagine needing to breed them. In MS at least, they can be had by the hundreds for a few minutes' worth of work.

#3 Guest_jase_*

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Posted 10 March 2008 - 10:16 PM

Here are 3 (lousy) pics of two females I'm considering to be "gravid". Any doubts? Is the black spot in front of the vent a sure sign, or can a female just be fat and have that marking?

P3050010.JPG
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P3050013.JPG

#4 Guest_fundulus_*

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Posted 10 March 2008 - 10:50 PM

I'd say those fish are preggers. And I'm sure that in Vermont you don't have a choice but to breed them yourself if you want them.

#5 Guest_drewish_*

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Posted 10 March 2008 - 11:00 PM

This may or may not help. As a test for breeding fish outdoors, I attempted to do so with Gambusia since I find them everywhere. I went to a local reservoir and collected 5 fish, making sure at least one was male. I used an old whiskey half barrel with a plastic liner that totals 20g. I put one piece of water hyacinth in and of course it has duckweed. Both grew at a tremendous rate covering the barrel in a week's time. The roots of the water hyacinth were massive and stringy. Within a months time I had a bunch of young and a month later easily 50-100 fish. I never fed them so they fed primarily on insects and mosquito larvae.

Basically, if you want to pump them out, you may want to put a barrel of some sort outside this summer. I believe you will have more than you can handle by the time it is necessary to drain it.

#6 Guest_jase_*

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Posted 11 March 2008 - 12:01 AM

Thanks for quick responses.

Here in Vermont, catching them wild by the netload is not an option. Even raising them outdoors could only work for maybe 3-4 months of the year without a greenhouse. I'm willing to devote at least a 55-gallon aquarium to them if I can get a system down that will really be productive. My eventual goal is to be able to keep a few grass pickerel or other highly piscivorous fish without having to buy feeders (and the risk of disease that comes with them). Plus... I like raising stuff. :)

One thing I forgot to ask in my original post is how much water temperature and light regime affects these guys. Water is going to be room-temperature (78 or so) unless I really need to heat. But how about light cycle? Anyone got an idea on the ideal number of hours of light per day?

Thanks, Jase

#7 Guest_mikez_*

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Posted 11 March 2008 - 07:10 AM

My experience with the nippy little buggers was short lived and ended badly for all involved but I can offer my $00.02.
I brought home about a dozen from NC after a road trip one time. First thing I noticed was they had to be kept seperate, even in the collecting bucket 5 minutes after capture. They are belligerent SOBs.
I set them up in a ten gallon with lots of floating plants and duckweed. They so resembled feeder guppies that I assumed the same set up would work. Like you, I pretty much always had gravid females and rarely saw fry, none of which ever survived. I finally staked out the tank and watched closely for long enough to see that all the adults, even the mother, would actively search out and eat any fry. I increased the plants for hiding but it didn't help.
I gave up and fed the whole lot to a redfin pickeral.
I think the tank was too small and made it too easy for the adults to find the fry. In a bigger tank and/or with a really dense plant set up like Drewish said, you might do better. Also, I mostly fed flake. That might have been one reason they were hungry for meat. The outdoor setup may provide enough meat to keep 'em satisfied.

#8 Guest_jase_*

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Posted 11 March 2008 - 08:06 AM

Keep the info coming. :) Getting good input on what *doesn't* work in an indoor setup, but what does?

One specific question -- what do the fry do the instant they're born? Do they swim up or down? Real question is whether a breeding trap that assumes they'll pass out though the bottom is going to save them...

#9 Guest_teleost_*

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Posted 11 March 2008 - 09:27 AM

Since Gambusia overwinter in Chicago outdoors, I'm pretty certain outdoor tubs will produce longer than you think. I would also guess tubs to be the least expensive alternative when weighing the up front cost to production.

#10 Guest_mikez_*

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Posted 11 March 2008 - 11:25 AM

Keep the info coming. :) Getting good input on what *doesn't* work in an indoor setup, but what does?

One specific question -- what do the fry do the instant they're born? Do they swim up or down? Real question is whether a breeding trap that assumes they'll pass out though the bottom is going to save them...


I never saw which way they went when born but the few I did find were all in the floating plants. This is consistent with every other live bearers I've ever had.

#11 Guest_jase_*

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Posted 11 March 2008 - 11:47 AM

Since Gambusia overwinter in Chicago outdoors, I'm pretty certain outdoor tubs will produce longer than you think. I would also guess tubs to be the least expensive alternative when weighing the up front cost to production.

I hear you on this, and I do plan to set something up outdoors when it gets warm enough. It'll be May before I can do that: http://www.victoryse...m/frost/vt.html . In the meantime, I want to start getting some living fry out of all these gravid females I'm seeing! Plus, living where I do there's going to be at least 5-6 months of the year where any outdoor tank/tub would be quite frozen. Even if the fish can handle it, I don't want to be chopping through ice every time I want to get some feeders. :)

#12 Guest_jase_*

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Posted 12 March 2008 - 04:22 PM

Another question here: can anyone suggest an ideal ratio of males:females in the tank? In the interest of maintaining a long-term captive population, I want to keep genetic diversity high -- so I don't want to cull all but a couple males. But... right now I've got 13 males and 17 females. From watching them, looks like all the chasing that the females are subjected to could be taking away from their reproductive potential.

I know people keep saying that breeding gambusia is as easy as falling off a log, but I'm not finding it to be so, at least not in a an aquarium.

#13 Guest_jase_*

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Posted 20 March 2008 - 07:45 PM

Can anyone else help me out here? Brooklamprey provided a couple useful bits in another thread:
http://forum.nanfa.o...h...ost&p=33517
http://forum.nanfa.o...h...ost&p=33527
I'll give that approach a shot as soon as I can set it up.

I separated two females which I thought were gravid (see photos earlier in this thread) into a separate tank about 2/20/08. I subsequently moved one to a breeding trap on 3/13/08. Today is 3/20/08. I haven't seen any fry from either of them, and they're still looking just as pregnant as they did. What's going on here?

Are there other parameters I should be paying attention to?
  • I haven't tested the water chemistry, but I've got good biological filtration and don't suspect that anything is too out of whack.
  • Water temperature is probably upper 60s to maybe 70 degrees F.
  • Aquarium lghts are on weekdays from about 9am to 8pm, and the tank is in a space that gets a fair amount of ambient light during daylight hours.
  • I'm feeding generously with flake food and blackworms several times daily.
I guess my next step is to try to just pack a smallish aquarium with java moss and see how that goes. Other thoughts?

I know, breeding these guys is supposed to be a piece of cake. :(

#14 Guest_Skipjack_*

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Posted 20 March 2008 - 08:03 PM

Bird netting. Get it from the farm store. Wad it up and stick a bunch of it in the tank. Provides tons of hiding places.

#15 Guest_jase_*

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Posted 20 March 2008 - 08:10 PM

Bird netting. Get it from the farm store. Wad it up and stick a bunch of it in the tank. Provides tons of hiding places.

Aha, good call. Have you used this before? I've got a bunch of sinking yarn breeding mops in the tank, but netting seems like a better idea. I'll look for some this weekend.

Cheers, Jase

#16 Guest_Skipjack_*

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Posted 20 March 2008 - 08:15 PM

Using it now. Seems to be working. You can really pack it into a tank. I actually got the idea from a local fish farm. They pack it into their sumps to use as filter media in their recirculating systems.
I suck at plants, so this seemed like a decent alternative.

#17 Guest_jase_*

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Posted 20 March 2008 - 09:14 PM

Using it now. Seems to be working. You can really pack it into a tank. I actually got the idea from a local fish farm. They pack it into their sumps to use as filter media in their recirculating systems.

Yeah, I've seen it used in clarifying drums in small-scale aquaculture systems. I'll see if I can find some. Thanks.

#18 Guest_jase_*

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Posted 20 May 2008 - 10:13 AM

Alright, it's been too long since I gave an update here. I've learned two really important things about my mosquitofish , which may or may not translate to *all* mosquitofish. These were collected in Georgia last summer and sent to me by Jack Moore. I'm not sure if they're Eastern (G. holbrooki) or Western (G. affinis) -- haven't really tried to ID them yet. Gambusia affinis (Western) are more common, correct? What's the best way to distinguish between them?

Anyway, my 30 fish (roughly half-and-half male:female) were hanging out in room-temperature water for about 8 months. The females had looked *really* pregnant for much of the time, but I hadn't had a single drop. For a while I was convinced that they might be eating the young, but the fact that the tank was right next to my desk and I never saw a single baby makes me pretty confident they were simply not giving birth. Mosquitofish can do that -- hold their young without giving birth for a long time, it seems.

As I noted, I had moved one female to a breeding trap, where she hung out for about 3 weeks with nothing happening. Then... Spring started arriving, and sun started hitting the 29g where the fish were housed. All the sudden I saw babies in the breeding trap one day!

After talking to my LFS owner, I decided that temperature was probably the key. The fish had probably been hanging at about 70 degrees for the entire time, and simply would not drop. I added a heater and bumped temp to 83 degrees and started rotating my gravid females into a breeding trap. I got 6 broods in 3 days! That was back in early April.

My experience since then suggests that even at appropriate temperature with plenty of java moss and other structures, the gravid females simply will not drop as long as they are not isolated. Even in a 30-long (4' long) with plenty of space, I get *zero* drops until I isolate them in breeding traps. I can take a fish that has been gravid for months, put it in a breeding trap with some sprigs of java moss, and it will drop within 1 day.

So... seems like in order to get a drop, I need:
  • Temperature above 80 degrees F
  • Gravid female isolated in a breeding trap
As long as I don't meet *both* of those conditions, I get no drops.

The neat thing about this is that I've had pregnant females stay hugely pregnant for months, but not drop until I provide the right conditions. This makes it very easy for me to synchronize drops to get all fish of a single size class. I had my first series of broods (maybe 120 fish total) back in early April, and am just starting to get second broods from all those females. Now the females are bigger and producing bigger broods. It's quite a production facility at this point!

Many of those fish born in early April are already sexually mature and females showing quite pregnant. Once those F1 fish start producing, I'm going to have essentially unlimited feeders available...

Fun stuff. I really, really like this ability to synchronize broods. It definitely makes things easier in terms of tank and time requirements.

By the way, they take powdered flake as soon as they're born, and grow/breed on it just fine. I've been supplementing with a lot of blackworms, and that seems to help a bunch, too. Fun to see a tiny gambusia wrestling with a blackworm 3 times its length -- and the gambusia always win.

I've had no problems whatsoever with the fish nipping at each other. I've actually only had *one* fish die since I got them (excluding a few that died at birth). Pretty amazing little buggers. They're actually really neat fish to watch once you get to know them. The coloration on the fish is subtle, but really elegant. I love the spots on the tails and the pickerel-like eye stripe the males get.

Edited by jase, 20 May 2008 - 10:17 AM.


#19 Guest_fishlvr_*

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Posted 05 June 2008 - 11:35 AM

I would say you have holbrooki, since you said they have black spots on their fins, which affinis usually lack. Here is something else I found:
"G. holbrooki usually has seven dorsal rays and a gonopodium with prominent teeth on ray three. G. affinis usually has six dorsal rays and lacks prominent teeth on gonopodial ray three" - Natureserve.org

There is also something about dorsal ray counts in American Aquarium Fishes, but I don't have it with me, so I couldn't tell you what it says.

Mine will drop their babies at temps into the high 60's if given a 15-16 hour photoperiod. Of course, mine were collected from a creek that stays under 75F even during the hot summer months down here. Yours may have been collected from a pond or lake, which easily gets into the eighties during our hot GA summer.

#20 Guest_dmarkley_*

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Posted 05 June 2008 - 02:25 PM

I would say you have holbrooki, since you said they have black spots on their fins, which affinis usually lack. Here is something else I found:
"G. holbrooki usually has seven dorsal rays and a gonopodium with prominent teeth on ray three. G. affinis usually has six dorsal rays and lacks prominent teeth on gonopodial ray three" - Natureserve.org

There is also something about dorsal ray counts in American Aquarium Fishes, but I don't have it with me, so I couldn't tell you what it says.

Mine will drop their babies at temps into the high 60's if given a 15-16 hour photoperiod. Of course, mine were collected from a creek that stays under 75F even during the hot summer months down here. Yours may have been collected from a pond or lake, which easily gets into the eighties during our hot GA summer.


They have teeth on their gonopodiums? Sheesh, no wonder they are mean little fish........



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