Juvenile Bluegill ID help please

I netted five juvenile sunfish the other day in a creek near my house. They were all caught under cover in the shallows of the same deep, slow pool.

Three of them are approx. 2.5" long, and two of them are approx. 1" long

One of the larger fish has been ID'd as a Bluegill based on the dark dorsal spot. However, the other four do not have this spot.

Will the small ones develop it as they get larger or should it be visible at that size? What are the chances of the other four being a different type of sunfish, seeing as they all came from within 5" of each other in the creek?

Here are some pictures from when they were in my transport container, if that helps:















A pictures of a small one:



And the bluegill:




Thanks for your help!

Edited by Odessa87, 16 October 2010 - 11:42 PM.

They all look to be bluegills. The younger fish are the less their color shows under aquarium lights. In my experience, in areas where you find juvenile bluegills, you won't find anything else in that immediate area. Just don't let the coloring fool you. I have one in a tank right now that is coloring correctly while the lights have been off for a while, but 10 minutes after the lights have been on he's basically transparent. Yours look to be well-colored.

I agree - They all look like bluegill to me. However, I have found other sunnies in the immediate vicinity of bluegills like this, but not often. The spot on the soft portion of the dorsal does not always show up on all young fish. Regardless, they all look like bluegill.

They all look to be bluegills. The younger fish are the less their color shows under aquarium lights. In my experience, in areas where you find juvenile bluegills, you won't find anything else in that immediate area. Just don't let the coloring fool you. I have one in a tank right now that is coloring correctly while the lights have been off for a while, but 10 minutes after the lights have been on he's basically transparent. Yours look to be well-colored.

Thanks! That makes sense.

Do you think males are less aggressive towards other fish, or females? Or does it depend on the individual fish? One sunfish will be in a 90+ gallon with some other fish eventually, and I'd like to have a fairly non aggressive sunfish in there if possible (wishful thinking I know )

Also, do you know if males will build and defend a nest even if there are no females in the tank?

Thanks! That makes sense.

Do you think males are less aggressive towards other fish, or females? Or does it depend on the individual fish? One sunfish will be in a 90+ gallon with some other fish eventually, and I'd like to have a fairly non aggressive sunfish in there if possible (wishful thinking I know )

Also, do you know if males will build and defend a nest even if there are no females in the tank?

In most fish species, males arrive at spawning areas prior to females and begin to build and defend nests. I wouldn't expect a lack of females to make much of a difference. However, photoperiod and temperature are key cues to reproduction in fishes, and these are usually very different in an indoor tank under artificially lights, so you may not see any nesting behavior. If anything, I would expect females to be territorial.

Even still, in my experience bluegills are fairly aggressive and will eat most anything that will fit in their mouth. Other folks on here have far more experience with centrachids - they may be able to offer more insight.

In most fish species, males arrive at spawning areas prior to females and begin to build and defend nests. I wouldn't expect a lack of females to make much of a difference. However, photoperiod and temperature are key cues to reproduction in fishes, and these are usually very different in an indoor tank under artificially lights, so you may not see any nesting behavior. If anything, I would expect females to be territorial.

Even still, in my experience bluegills are fairly aggressive and will eat most anything that will fit in their mouth. Other folks on here have far more experience with centrachids - they may be able to offer more insight.

Hmmm. Perhaps I'll keep the two smallest around to grow out for awhile and play it by ear. And I'll read up on sunfish spawning behavior too.

As far as mouth size goes, what do you think the largest minnow an adult bluegill could eat? 3"? 4"? Larger? Thankfully these guys aren't green sunfish with huge mouths, so hopefully I can have some semblance of a community type tank once everyone is full grown.

As far as mouth size goes, what do you think the largest minnow an adult bluegill could eat? 3"? 4"? Larger? Thankfully these guys aren't green sunfish with huge mouths, so hopefully I can have some semblance of a community type tank once everyone is full grown.

This depends a lot on how big your 'adult' bluegill is. A few thoughts:
-It will take a while for your bluegill to reach adult size. I would guess you could have a nice community tank for quite a while before the bluegills grew large enough to be a problem.
-If you offer more cover, your small fish will fare better.
-Madtoms or bullheads will probably be just fine (given their behavior and spines).

Good luck!




EDIT: The previous post was meant to say "If anything, I would expect females to be less territorial"

EDIT: The previous post was meant to say "If anything, I would expect females to be less territorial"

What size do they need to be in order to reliably sex them based on their vents? I assume I will have to use a magnifying glass regardless.

What size do they need to be in order to reliably sex them based on their vents? I assume I will have to use a magnifying glass regardless.

3 to 4" and magnifying glass helps. By that time should be easy to manually express gametes. Otherwise same as with green sunfish.

Use following link: http://forum.nanfa.o...92-vent-sexing/

I like to use behaviour instead. Female bluegill coming from your area have lower parts of bars on sides broken up into irregular greenish-gold spots. Only males will have silvery blue patch along lower jaw when fish are young adults. Larger females will have same character.

Edited by centrarchid, 18 October 2010 - 03:20 PM.