Mosquitofish, which one?

[Fishoreel]

Is there a way to tell Gambusia holbrooki from Gambusia affinis? I've had them forever but didn't know there was two types. I live near South GA and North Florida.

 

[WahooWillie]

Both species have been introduced into the other one's ranges, but if you are in the south, and Atlantic drainages, then it is probable that you have holbrooki.

 

[Fishoreel]

Ok, do they have any physical difference? I noticed the gambusia in the Satilla river where I live have a lighter color than the fish I had from a pond in FL. (could they be different colors because of the habitat they were in, rather than species? (i'm not sure that's why I'm asking)

 

[jpac716]

affinis is a lighter color I have them in my pond holbrooki seem to be slightly darker

 

[WahooWillie]

Color is not a distinguishing characteristic that can differentiate the two Gambusia. Like you said, Fishoreel, color can be largely influenced by habitat. If you really want to know the difference, you need to look at the gonopodium on the males. The gonopudium ray has a series of 'teeth' on it in holbrooki, and is smooth on affinis. You'll need magnification to see this. There are dorsal fin ray counts too, but in all honesty, I wouldn't bother...

 

[Fishoreel]

Ok, thanks for the information. I couldn't find the difference anywhere else.

 

[buctrose]

To tell the difference you have to count the number of rays in the anal fin.