Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations gams through winter

this is aimed at meadowlark, but would love responses from any or all.......

as some of you may recall, last April 05 i "stocked" nine mosquito fish in my pond (~1 acre). by September/October 05 there were perhaps 10's maybe 100's of thousands (i hesitate to say millions but it looked like it).

as the water temps continued to decrease going through Nov/Dec 06 and into Jan 07, i saw no gams around the shorelines and assumed they moved to deeper warmer water. it was only yesterday (after a few days in the 50's and low 60's) that i have seen any, and only a few individuals near the shoreline.

my questions....
what is the typical lifespan of gambusia?

i had the first ice-over i've ever seen in 11 years that lasted about 2 weeks in mid-january, did the gams survive just fine?

will i see a great emergence of them as the weather continues to warm?

what water temp do they need to start breeding again assuming i still have breeders?

i'm not sure if i should/need to stock additional gams, although it probably wont hurt a thing no matter how many are in pond, correct?

DIED there are about 150 species of gams. Here is some info on 2 common types in the US.

http://www.fishbase.org/Summary/SpeciesSummary.php?id=3215

http://www.cnr.vt.edu/efish/families/poeciliidae.html

thanks for those direct links ewest,

regarding reproduction, on the fishbase site they state:
"Medium, minimum population doubling time 1.4 - 4.4 years (K=1.20; tmax=3; Fec=10-60)"

that sounds really off......my population practically doubled as you stood there and watched it.

but the virtual aquarium site states:
"Reproductive Habits:
· Mature rapidly, and may reproduce 4-6 weeks after birth
· Spawning occurs mid-April to September in water 15.5-20°C
· 3-4 weeks for young to develop inside female, young are born live
· 1-354 young per brood"

The reproductive rates i saw in my pond are more consistent with the virtual aquarium......(i.e. 1-350 fish per brood versus population doubling every 1.4 to 4.4 years)....

whether or not they all made it through the winter though??.....what do other pondmeisters see in their ponds?

I put 300 g. affinis in very muddy water about 3 weeks ago. Some of them appeared to be pregnant. Sometimes I don't see any for a while, sometimes I'm surprised to see a little group of them here and there. No ice yet, but it's been cold here. I think the water temp is in the 40's.

bobad, i think (hope) you'll be as surprised as i was at how many you'll have in a couple months. i forget....do you have any (gam) predators in pond yet?

I hope you're right.

At present, gams and a few tiny crawfish are the only living things in my pond.


But I love gams. Unlike the vulnerable fatheads, they're tough little survivors. I think warm water would get a much quicker doubling rate than the web pages state. I've seen them really explode in small ponds.

My favorite forage is ghost shrimp, but I can't find a cheap source. I want about 5,000 of them, but that would cost me $33,000! And that's with a quantity discount! So,,, I can see a lot of gams in my future!

DIED as stated there are many species of gams. They are not all the same. That min, pop. time I think is in a wild envior. (predators) over time (not 3 days after hatching) - and is a range. The med. time is a comparison to other fish. Some fish produce over 100,000 eggs a year so the gams are med in repro. status. One of the species I linked has a range up to Ill. so that one should survive Calif. with no problem. If I recall their life span is 2 yrs. Will check that.

bobad, there was a past thread on a pretty cheap source for ghost(grass) shrimp eggs. Seemed there were live ones too. The price seemed to be reasonable. Will try to find it; maybe someone else has it earmarked.

Bobad, you gotta be kidding. That's $6.60 per shrimp.

Made a mistake Dave. That's what I get for trying to multiply in my head.

Price for 5000 is only $2250, or .45 each. I'm in the wrong business!

Hey Burg,

AFAIK, you can't buy ghost shrimp eggs. Maybe you're thinking of brine shrimp. (AKA fairy shrimp, AKA sea monkeys) You can dry the eggs and store them for years, and they will still be viable. In fact, I think they must dry out in order to stimulate them to hatch when wetted again.

I gotta bulid a minnow trap to catch some more gambusia. I think we used to build them but I don't remember how.

Gotcha, bobad. No grass shrimp eggs. There was still a reasonable source for the little guys. Still looking. Minnow traps can be purchased for 5-6 bucks at Walmart or Academy. They are in 2 halves. Like 2 cones with the ends bent in and holes in each end. There is a large spring pin to hook the 2 parts together. They are very effective. They come with various size holes for capturing diff. size bait.

D.I.E.D.,

Your Questions followed by my answers:

my questions....
what is the typical lifespan of gambusia?

Typical depends on the predators but two to three years lifespan in the absence of being eaten are the rule.


i had the first ice-over i've ever seen in 11 years that lasted about 2 weeks in mid-january, did the gams survive just fine?

Yes, they survived. The natural range of Gams includes Illinois and Indiana and they are reputed to withstand air temps of -30 deg F to 100 deg F

will i see a great emergence of them as the weather continues to warm?

Yes, absolutely

what water temp do they need to start breeding again assuming i still have breeders?

Not sure of this number but I have seen spawning in the 60 to 70 degree range and of course above.

i'm not sure if i should/need to stock additional gams, although it probably wont hurt a thing no matter how many are in pond, correct?

D.I.E.D., in 1983 we had a really bad freeze…even had ice on Galveston Bay. At the ranch we had pond ice a couple of inches thick for almost 10 days. Gams did just fine.

One more data point, they are livebearers that typically have 3-4 broods per year of about 100 young per brood. If you give them a grassy shoreline, you will never have to restock them and will have a recurring, free forage base for your small LMB and BG.

Gams….I wouldn’t have a pond without them.

Bobad,

They are a very small fish... when I need some to give to a friend or use as bait I run one of those telescoping swimming pool skimmer poles with the very fine mesh along the shoreline. I catch hundreds of Gams that way. Much more effective than traps for me.

thanks so much ML.....i was getting worried they either died off, or were decimated by the 2 week ice cap.

i may still stock additional gams anyway to mix up the gene pool, i am a little worried that all these fish came from an original group of nine, and figure i should discourage the establishment of vast shallow submerged trailer parks along my pond shorelines....ok sorry, bad joke.

Bobad, dittos to ML's gam catching method, when fellow pondmeister jeffhasapond came over to my place, he used a long handled swimming pool skimmer on the gams with quick and easy success.