Mosquitofish in CT

Western mosquitofish have been introduced far and wide outside their native range. Eastern mosquitofish less so, though there are some introduced populations scattered across the country. The reason for introduction is, of course, mosquito control, though it turns out that their diet often doesn't include a large mosquito larvae portion.... so exactly how effective they are for that purpose is questionable. Whether they are good at mosquito control or not, Gambusia have been spread all over the place. That includes CT. Western mosquitofish have ended up in the West River and a small pond in New Haven, as well as the Norwalk River. Their survival in the winter is tenuous at best, so most places in which mosquitofish have been introduced this far north don't necessarily still sustain a population. Finding them anywhere up here is a bit of a surprise.

On Monday, Noah and I found mosquitofish in a large Central CT pond.

Spot the Gambusia.

Our actual query remained elusive: central mudminnows and bridled shiners. And the presence of the Gambusia may have been why. As recently as 2017, electrofishing surveys hadn't turned up mosquitofish in this pond. I was completely blown away when Noah finally brought one to hand, we got it in the photo tank and I looked at it closely. It was pretty clearly a mosquitofish, but we still don't know which one. My money is on Western, Gambusia affinis. If it's an Eastern mosquitofish, Gambusia holbrooki, it's the first time the species has been recorded in CT. Visual identification of mosquitofish isn't especially easy. 

So, though we didn't know it at the time, the parameters of our next trip together were now set. There were large schools of these fish in the first location we searched, and a few others elsewhere. Clearly there had been somewhat of a takeover by these mosquitofish. I emailed Steve Gephard, DEEP Supervising Fisheries Biologist, as soon as I got home and got the photos uploaded. There was no record of mosquitofish in that pond at all. He suggested we go back and collect some. That'll give me another chance to catch one too, and if they turn out to be affinis, it'll be a new species for me.

Before going home though, Noah and I bounced around a handful of different streams. The first two were absolutely lifeless. We didn't see a single fish in either. Both had new species potential, but without seeing fish, we weren't especially confident. I chose a third stream just on the basis of being a morale booster. We needed to catch some stuff, and the carp, bass, and sunfish there would likely oblige. And, though it was actually a pretty slow bite, we did catch some stuff. I fouled a pretty substantial largemouth, which was a bit disappointing, and we both got some bluegills. The bluegills were rising regularly to small insects that were ending up in the water from lawn mowing in the neighborhood. It wasn't a bad way to end the day.

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