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Need help identifying fish species found in TN

Started by Guest_Jaymes_* , Aug 18 2008 11:44 PM

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15 replies to this topic

#1 Guest_Jaymes_*

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Posted 18 August 2008 - 11:44 PM

Hello! I'm new to this forum, so I hope this is an appropriate place to post this thread...

I've kept tropical aquariums for quite some time. Biology is my favorite subject, as I am in high school. I am taking my third bio course this year. I've always been very interested in nature and anything I could catch and study (and soon release, of course :smile2:

). I recently found a fish species in Tennessee that interested me, but I can't seem to find out what it is.

In July I spent two weeks in northern Tennessee working at a camp. I found the fish in a small, spring-fed lake. They're quite plentiful, and range in size from .25" - 2", approximatley. They're a light brown, dusty color. Many of them have what I thought was a gravid spot, but once I examined some more closely, it seems it may just be darker coloring on the scales. I collected 8-10 larger fish ( 1.5"-2"). Assuming these were livebearers, I expected to find that I could differentiate between males and females by the male's gonopodium. However, each of the fish I caught seemed to be female. Out of 8-10 fish, I would have expected at least one male - or maybe these weren't livebearers after all. Are there any livebearing fish native to Tennessee? Or could these have been a non-native species, maybe released from an aquarium owner? They may not be livebearing at all, although they seemed to be so similar to wild type platies.

I would be very interested to know what kind of fish these were. If anyone could give me a hand identifying them, I'd really appreciate it.

#2 Guest_truf_*

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Posted 19 August 2008 - 12:58 AM

Welcome Jaymes!
I have sent you a message.
-Thom

#3 Guest_itsme_*

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Posted 19 August 2008 - 01:00 AM

Sounds like Gambusia, mosquitofish. Don't know if they are native to TN, but they certainly do live there. They have been widely introduced as mosquito control. Now considered a damaging exotic in many places because they prey on native fishes and amphibians. If you keep them with other fishes, you will likely find they they are quite aggressive and damaging to them in close quarters. In the wild, they tend to stay in the shallowest of waters for safety's sake, to avoid larger predators. Here's a couple photos: http://jonahsaquariu...holbrooki01.htm

#4 Guest_Jaymes_*

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Posted 19 August 2008 - 02:07 AM

Just to clarify - the fish were never put in an aquarium, or with captive fish. They were simply put into a container with water from the pond and released a few minutes later.

#5 Guest_truf_*

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Posted 19 August 2008 - 01:57 PM

I caught several Gambusia affinis a couple of weeks ago, and all of them were female. I wonder if the ratio is always highly skewed toward females. Perhaps one of our resident experts could explain.
-Thom

#6 Guest_Jaymes_*

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Posted 19 August 2008 - 05:00 PM

I know that some enviromental factors can have an influence on the male/female ratio in some species, but I sure would like to know exactly what was causing the trend in this situation. I suppose it would need a little further study. I guess it's just another reason to go back to Tennessee - after coming home to Indiana, I'm looking for every excuse I can get to take another trip down. :rolleyes:

#7 Guest_truf_*

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Posted 19 August 2008 - 09:04 PM

I know that some enviromental factors can have an influence on the male/female ratio in some species, but I sure would like to know exactly what was causing the trend in this situation. I suppose it would need a little further study. I guess it's just another reason to go back to Tennessee - after coming home to Indiana, I'm looking for every excuse I can get to take another trip down.

Hey Jaymes,
Where is your home drainage? Please add it to your profile. (I'm particularly curious because I'm also originaly from Indiana).

-Thom

#8 Guest_Jaymes_*

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Posted 19 August 2008 - 11:00 PM

Home drainage?? :mellow:

Umm... explain to the noob please?

#9 Guest_truf_*

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Posted 20 August 2008 - 06:44 AM

Home drainage?? Umm... explain to the noob please?

Oh, sorry. :blush:

What watershed is near you? (river, major creek, etc....) Alternately, what is the town in which you live? You can even tell us the general area in which you live, ie: (South Central Indiana) Include this info in your profile; lots of people like to see who's from where! In addition, it gives everyone a better understanding of the ranges of fish in your area, which in turn can help with identification.

#10 Guest_Newt_*

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Posted 20 August 2008 - 10:59 AM

I think there's a simpler explanation than wacky sex ratios. You said you caught all larger fish- male Gambusia stay very small. They may have just been slipping through your net.

#11 Guest_truf_*

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Posted 20 August 2008 - 04:39 PM

I think there's a simpler explanation than wacky sex ratios. You said you caught all larger fish- male Gambusia stay very small. They may have just been slipping through your net.

That is a reasonable explanation. I was suspecting either that, or that I was seeing and targeting larger fish with my net. I think that may have been what happened with Jaymes also.
-Thom

#12 Guest_Jaymes_*

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Posted 20 August 2008 - 04:40 PM

I think there's a simpler explanation than wacky sex ratios. You said you caught all larger fish- male Gambusia stay very small. They may have just been slipping through your net.

I bet that's it! I caught only large fish on purpose, so I could study them more easily. That makes perfect sense. Thanks!

#13 Guest_uniseine_*

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Posted 20 August 2008 - 08:37 PM

<clip>
In July I spent two weeks in northern Tennessee working at a camp. I found the fish in a small, spring-fed lake.
<clip>

Being spring-fed would explain how gambusia can live through the winter. Same thing happens all over Nebraska.

It doesn't explain how the Dambusia got there.

#14 Guest_Jaymes_*

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Posted 20 August 2008 - 11:05 PM

Being spring-fed would explain how gambusia can live through the winter. Same thing happens all over Nebraska.

It doesn't explain how the Dambusia got there.

How does it being spring-fed allow them to survive the winter? The spring is freezing cold even in July...?

#15 Guest_Newt_*

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Posted 21 August 2008 - 11:16 AM

Springs are the same temp all year; in middle TN that temp is 55-57 F (the average annual air temp).

#16 Guest_khudgins_*

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Posted 21 August 2008 - 11:46 AM

How does it being spring-fed allow them to survive the winter? The spring is freezing cold even in July...?

Because what's freezing cold to you isn't freezing cold to the fish. And the water coming out of the spring will be the same temp. in February as it is in August. Even if the top freezes up, the fresh water from the spring will stay ~ 60F (or whatever the ambient ground temps are) through the winter, and the fish will just collect in the warm spots down near the new-fed water and hang out 'til thaw.

At least, that's how I understand it. IANAF/GWE (I Am Not A Fish or Ground Water Expert). I'm sure if I'm wrong the better informed folks here will correct me. (please do!)