Pond Boss Forums STOCKING A NEW POND Types of fish to choose Gambusia, an invasive species

I don't mean any disrespect to those who have stocked Gambusia, but I feel it's important to point out some possible negative effects.

"Predation of amphibian eggs and interference competition with tadpoles, resulting in injury or death to individuals. May have a negative influence on some frog species' choice of breeding habitat. G. holbrooki has been shown to predate upon the eggs and tadpoles of the critically endangered yellow-spotted tree frog (see Litoria castanea in IUCN Red List of Threatened Species), endangered green and gold frog (see Litoria raniformis in IUCN Red List of Threatened Species), and vulnerable golden bell frog (see Litoria aurea in IUCN Red List of Threatened Species) in Australia (NSW National Parks & Wildlife Service, 2004). Gambusia spp. have been implicated in the decline in the range and abundance of native fish species worldwide (Lloyd 1990) through predation and interference competition (McKay 1984; Howe 1995; Ivanstoff and Aarn 1999; Knight 1999). The species is purported to impact on macro-invertebrates such as rotifers, mayflies, beetles, dragonflies and molluscs (Anstis, 2002)."
ARTICLE

"Specific examples of their negative effects include a habitat shift and a reduction in numbers of the threatened Railroad Valley springfish Crenichthys baileyi in springs in Nevada (Deacon et al. 1964) and the local elimination of the endangered Sonoran topminnow Poeciliopsis occidentalis in Arizona (Moyle 1976a; Meffe et al. 1983, Meffe 1985). Western mosquitofish use the same habitat as the plains topminnow Fundulus sciadicus and have displaced these topminnows and other species with their aggressive behavior (Whitmore 1997). The mosquitofish is also responsible for the elimination of the least chub Iotichthys phlegethontis in several areas of Utah (Whitmore 1997). Meffe (1983, 1985) found that mosquitofish are very aggressive, even toward larger fish. They often attack, shred fins, and sometimes kill other species. Mosquitofish are known to prey on eggs, larvae, and juveniles of various fishes, including those of largemouth bass and common carp; they are also known to prey on adults of smaller species (Meffe 1985; Courtenay and Meffe 1989). Courtenay and Meffe (1989) listed impacts on a variety of native fishes.
Introducing mosquitofish also can precipitate algal blooms when the fish eat the zooplankton grazers (Hurlbert et al. 1972), or in an increase in the number of mosquitoes if the fish eat the invertebrate predators (Hoy et al. 1972). Introduced fishes, including mosquitofish, are likely at least partially responsible for the decline of the Chiricahua leopard frog Rana chiricahuensis in southeastern Arizona (Rosen et al. 1995).
Mosquitofish, and other introduced poeciliids, have been implicated in the decline of native damselflies on Oahu, Hawaii. Often the distributions of the damselflies and introduced fishes were found to be mutually exclusive, probably resulting from predation of the fish on the insects (Englund 1999)."
ARTICLE

"Mosquitofish are aggressive foragers, feeding on a variety of prey, including the eggs, fry and larvae of native biota (Goodell et al. 2000). This is presumably the reason why they were widely introduced as a biocontrol agent against mosquitoes (and mosquitoborne diseases) in the early and mid- 1900s (Krumholz 1948). Presently, they are considered among the 100 worst invasive species worldwide (Lowe et al. 2000)."

"The mosquitofish diet is typically composed of zooplankton, drifting and benthic invertebrates, and terrestrial and neustonic prey (Lloyd et al. 1986; Garcia-Berthou 1999). Mosquitofish are known to significantly alter aquatic communities because of their direct predatory effects on these organisms, particularly zooplankton (Hurlbert et al. 1972; Hurlbert & Mulla 1981; Harris 1995; Margaritora et al. 2001; Blanco et al. 2004)."
ARTICLE (pdf)

I appreciate the benefit that Gams can have in pond management, however I have decided not to aid in the distribution of these fish. If they show up in my pond I'll be OK with it, but I would rather stock other indigenous small fishes.

Good post, GW.

GW I commend you for looking for the answers in your quest. There is a lot we don't know but also a lot that has been addressed by science if we will look. Always good to have someone point out some of the science.

No offense taken GW.

I stocked gams with my eyes wide open. In my area, gams are ubiquitous. Every stream, pond, lake, and mudpuddle has gams. Because they are live bearers, they are among the easiest fish for birds to transport. Even if I had never stocked them, my pond was guaranteed to have them sooner or later.

Over the millenia, native species that share habitat with gams have fully adapted to them. Many fish in fact rely on them for forage. If my local frogs avoided them when choosing a site to lay their eggs, I bet they would have to hop for 300 miles!

I may be wrong, but I don't think that article is aimed at areas in which gams are native and plentiful. I can see where they could upset species that are not adapted to them. IIRC, they are even illegal in some states, and rightfully so.

Why is it that Gams don't seem to do well in the northern 1/2 of the USA? I've been told that they usually dissappear within a year of being stocked here in NE just like FH minnows.

Shorty, I think they evolved in the south. Maybe the cold winters break up their breeding cycle too much.

bobad, I guess you could say that when it comes to stocking Gams, it all depends.....

Oh sure GW, now you tell me!!! First the GSF fiasco now this!

In Northern California most counties have been giving away Gams for quite a while. They are in probably every body of water of any significance.

We may never know the effect that LMB introduction has had in some environments. I would think that the voracious feeding habits of fry-to-juvinile-to adult LMB has had some significant impact on native species in certain areas. LMB have been introduced all over the country and I'm sure many, many times put in areas where the didn't previously exist.

All that being said it's always important to consider the effect of relocating/introducing a species into an ecosystem.

Good post GW.

Exactly!

If you stock endangered fish or fish with delicate breeding habits, gams could be a problem. If you stock LMB, BG, RES, crappie, catfish, etc, I don't think there's much down side to them.

I think gams get a bad rap on being egg stealers. Believe me, gams will not venture down to the LMB and BG spawning beds. The instant they do, they're lunch. They will surely eat insect eggs and even fish eggs laid right against the shore.

Thanks jhap, sorry 'bout the timing...

bobad, I think the Gams would prey on LMB fry more than eat the eggs themselves. Anything smaller than they are will have a hard time. Still, that might not be bad for some pond management purposes.

Guys there are at least 20 different types of gams. All are not invasive as affinis is native to many parts of the US. It still creates the problems GW noted. Here is some info from FishBase.


Gambusia affinis
Mosquitofish

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

Food items

detritus detritus debris unidentified (not available) juv./adults
nekton finfish bony fish Gambusia affinis New Zealand juv./adults
nekton finfish bony fish Poeciliopsis occidentalis USA juv./adults
zoobenthos insects insects unidentified USA juv./adults
zoobenthos insects insects unidentified chironomid larvae New Zealand juv./adults
zoobenthos insects insects unidentified chironomid pupae New Zealand juv./adults
zoobenthos insects insects mosquito (not available) juv./adults
zoobenthos insects insects nematoceran Diptera Australia juv./adults
zoobenthos insects insects aquatic Hemiptera Australia juv./adults
zoobenthos insects insects unidentified psychodid larvae New Zealand juv./adults
others other terrest. invertebrates n.a./terrest. insects unidentified terrest. collembolans New Zealand juv./adults
others other terrest. invertebrates n.a./terrest. insects ants Australia juv./adults
others other terrest. invertebrates n.a./terrest. insects unidentified terrestrial hemipterans New Zealand juv./adults
others other terrest. invertebrates n.a./terrest. insects unidentified terrest. Hymenopterans New Zealand juv./adults
others other terrest. invertebrates n.a./terrest. insects unidentified terrestrial lepidopterans New Zealand juv./adults
zooplankton plank. crust. cladocerans Daphnia magna (not available) juv./adults
zooplankton plank. crust. cladocerans Daphnia pulex (not available) juv./adults
zoobenthos worms polychaetes unidentified aquatic oligochaetes New Zealand juv./adults

Where I live Gambusia Holbrooki is native. It's also one of the problem Gams that has been introduced to every continent except Antarctica. I don't think I'll stock them because I would rather have the several native species that they would displace.

Whether you stock Gams or not, they are still a fascinating fish to read about.

I have Gams in my pond and have never seen them eaten by the LMB or the GSF, I doubt there capabilities as a forage fish. I introduced them to the pond a few years ago from a local stream. One bucket of perhaps 40 adults and young and they have established a healthy breeding population in my 1/4 acre pond.