Pond Boss Forums STOCKING A NEW POND Creating the food chain Gambusia and Fathead Minnow Competition/Compatibility

Dave,

Gambusia are very tolerant of a wide range of bad water conditions. They are real survivors, and one of the last species swimming when small ponds go bad and/or dry up.

I think gambusia is about the slowest fish in the pond. They survive by hiding, not out swimming predators. I keep hearing they eat eggs, but most beds are in water far too deep and open for them to venture into. If they even come close to LMB or BG beds, they are instant fish food.

The state of MI did some studies the determine if there was use in bringing gamusia is to help with mosquito control, and found that bluegill did a better job of keeping the mosquitos controled here. The gambusia couldn't handle the colder northern waters, and died as the waters cooled. Tried to find the study again, but could remember where I read it.

ML, I got the picture but also can't post it. It shows a 1.5 inch fish. Fatties get larger but probably not very many live to max size.

Ok, if they are both good reproducers and slow swimmers, does this indicate that fatties just don't have the survival instinct of a Gambusia?

ealong59, I think this is the study you reffered too.

http://www.michigandnr.com/PUBLICATIONS/PDFS/ifr/ifrlibra/technical/reports/2003-2tr.pdf

Here's ML's Gambusia Pic. It's what I remember ours looking like. They might have made it to 2", but that would have been a big one.

Facts from FishBase, SRAC and EFish.

There are at least 17 different species of gambusia native to the US and at least 3 more non-native ones here. Two of the non-native species are the most common and one covers the south 3/4ths of east coast area and another the Miss. drainage.

The ones I checked average 50 offspring per hatch/birth , once a month , April to Sept. That is 250-300 offspring a year. Most have a fast population doubling time 15 mths but one of the more common species has a medium population (1.4 - 4.4 yr)doubling time. There are several species which are native to small specific areas of Texas which has more different species than any other state or area. Avg. length 3-6 cm ,age 2 yrs. Food -zooplank- cladocerans , polychaetes/worms/larva , insects , bony fish (cannibal),other terrest.invertebrates. Climate - subtropical; 12 – 29°C.

Fatheads. Fast population doubling time of 15 mths. Spawns April - Aug. and average fecundity 6,803-10,164 . Age 2 yrs , length 10 cm. Food - plank.- copepods, benth. crust.- ostracods ,insects ,benthic- algae/weeds , bryozoan statoblasts, other. Climate- temperate; 0 – 33°C. Females spawn at frequent intervals, up to several times a week. A fractional spawner.

Here is a link. to some pics

http://www.fishbase.org/ComNames/ComName...5gambusia%25%27

I'm curious about the phrase "population doubling time"...can you elaborate ? It makes it sound like both species produce equivalent offspring over a 15 month period.

FishBase uses that concept and divides the fish in groups under that category . The groupings are fairly wide for example medium doubling time is a period from 1.4 to 4.4 yrs and fast is less than 15 mths. It takes into account, I think, a number of factors including fecundity , age of sexual maturity ,life span, natural morts., etc. The time it takes for a population to double. It gives a more accurate measure of a species ability to grow its population.

WOW! I am gone for 2 days and already three pages!

Just to clarify, i believe that the fish that i am referring to is the Gambusia Affinis, also know as the western mosquito fish. I am sorry if i caused confusion because i didnt clarify.


The main issues/concerns that i have with introducing gambusia are:

1. Do Gambusia Minnows eat Fathead minnow eggs/fry?

2. If they DO is it a significant amount?

3. Do Gambusia Minnows and Fathead minnows compete for the same spawning grounds, and food.

4. Would have been about spawning numbers, but thanks to Ewest and several others that has already been resolved.

Right now I am leaning towards not stocking gambusias and instead revamping my Fathead minnow spawning structure.


Thanks - Jighead

Bill Cody,

I truly like your idea of adding scuds to my pond. As i flyfish frequently for trout, i realize the importance of scuds in a trouts ecosystem and diet. In fact, i believe that the importance is even greater to a pond trout than it is to a stream trout.
The first time I ever actually thought about introducing a substantial population was when i read your post.

So naturally i have a few questions:

1. Is there a easy way to get a supply of them?

2. It is very possible for me to culture them in large tanks, then seine them out into my pond. Is it best to buy a small population and then culture a large population before introducing them into my pond? Or are they prolific enough that they do not need my help?


Thanks for the excellent idea, I am excited about starting my own population.


- Jighead

Jighead :

I hope I did not confuse things for you. Sometimes info can do that. With a trout pond I would do what Bill suggests.

Look at this link about your questions.Then open # 2 from the list.

http://www.scirus.com/srsapp/search?q=%2...mem=jnl#results

Ewest, as usual, thanks for the info.

Jighead, Check out ColoradoFisheries.com. They should be able to help you and provide answers to your questions about scuds for trout. Please keep us advised about your progress with scuds (Gammarus lacustris). If you have a fair amount of shallow water weed beds the scuds should do quite well for you. If you have a small secluded pond with no fish in it or just minnows you could develop a population that produces a constant supply of scuds.

I wouldn't worry about gambusia and fatheads competing for spawning areas. Gambusia are live-bearers, and don't need spawning areas.

GAMs have major survival advantages over FHM that are directly related to reproduction.

GAMs breed "on the fly". They mate while swimming and when inseminated, the female GAM can produce multiple broods without further matings. They are vulnerable during the act of mating only for a few seconds.

GAMs don't lay eggs. The only way for the eggs to be lost is for the female to be eaten. Though fecundity is lower, have much better survival of critical brooders.

FHM minnows spawn. Males are the critical brooders. They protect the eggs. Males are vulnerable to predators while protecting their nest. When the males are gone, there is no more reproduction.

FHM minnows need spawning habitat.

They eat different things and FHM are better to have but if the forage must reproduce the GAMs will do better. In any pond still supporting FHM reproduction, however, GAMs probably should be avoided.

My pond is just over 2 years old. The number of fish I've personally stocked will barely cover the bottom of a 5 gallon bucket.

Thanks to hurricane Harvey, I've got both GAMs and what I think are Rosie Red FHM (Their tales are red anyway). Both have survived naturally against a swarm of different predators, tho the GAMs far outnumber the the reds.

The GSF tend to spawn in inches of water right against the bank and I watch them religiously. Can't say I've ever seen either species ever get brave enough to venture into a guarded nest. However, once those fry are self motivated to leave home, I have no doubt their survival rate is affected by both GAMs and FHM, but only initially. Gape for both minnows is very limiting as to what they can swallow.

I will say this tho, both are very adept at feeding on pellets. Especially when its hydrated first. They come running as fast as they can when I ring the dinner bell.