Age of a gill

[Jeremy R. Mayo]

How do you tell the age of a gill.
We caught a gill today that is a rariety. He had stipes like most of the lil guys that we catch that are under 5" but this bull was huge. Already over 8"s I thought that stipes indicated youth. But his size indicated full grown. He didnt have the coloration that most of the bulls his size do around here. I brought him home and put him in the aquarium until I can figure out what to do with him. Somebody help on this one.

[Bruce Condello]

You can start by posting a picture of the fish! :-0

The most accurate way to age a 'gill is to take a scale sample, which can then be pressed on to a clear slide, and the rings on the scale can be read like rings on a tree.

Round your parts a bluegill grows faster and grows more throughout the year, but will live fewer years. I'd imagine that a 5 year old (age-5) bluegill down south is a pretty old fish. Up here in Nebraska I don't consider a bluegill old until it hits age-7 or age-8. In the end it's interesting to note that the top-end size bluegill are similar throughout the country.

What if you don't have the capability to take a scale sample and read it?

One of the keys to the age of a bluegill lies in the size of the fins and the eyes. A really fast growing bluegill essentially outgrows it's fins and eyes. Bluegill in stunted populations (and this is true of crappie too) will often have big oversized eyes because the fish are old. Some of the bluegill in my ponds have little tiny eyes because they are young and fast growing.

Another way that biologist measure the age of a fish is to remove the otoliths or "earstones" of a sacrificed bluegill. These can be cross-sectioned to reveal information about the age of a fish.

[Zig]

Gonna have to give the otoliths the nod for being more accurate then scales. Scales can and will show differing growth stages between multiple samples. The otoliths aren't as variable.

These are un-prepped slide shots from the bluegill I worked with from Sunday's trip.
A complete otolith at 250x:


This is an unprepped scale sample that was taken to verify software operation:


Aging isn't something that is as easy as it sounds, as most real life samples aren't as defined as you find search the web.
I find otolith preparation quite tedious at times, and I have only dealt with older specimens. I can only imagine what goes into dealing with fry stage sampling.

[Bruce Condello]

Zig's right, although scale samples can vary in their accuracy depending on how long and cold winters are in a particular region. Areas of the world where the fish lives for months in 36 degree water, then months in much warmer water tend to show more well defined rings.

Zig's also right about there being an art to reading scales. One biologist may think a fish is age-4, while another might say age-5. Scale sampling is a tool that has more scientific usefulness the larger the number of fish sampled.

[Jeremy R. Mayo]

Im just a simple minded country boy. I look at a puppy and if its got big feet I know its gonna be a big ole dog. If a horse has huge teeth then its prolly pretty old and if a turkeys spurs are really long then hes on up in age. I can tell the age of a deer by the length of there nose. Theres gotta be a tale tale sign of fish ageing. One without a microscope.

Heres the pics :-)

[Jeremy R. Mayo]

Yep thats bull minows. Its true what you say bruce. Bluegill love the lil fishies better than anything. Well the bigger ones anyway. Theres a gill in that tank thats about 3 1/2" and yes ive caught him with 2" minnows hangin outa his mouth. I make sure to dump him some crickets and bread crumbs in every other day till he gets big enough to handle them though. HOW OLD IS MY FISH!!!!!!

[shooter]

ok Jermey i gonna bite,at 3 1/2 '' not more than a year in that tank.

[Jeremy R. Mayo]

Nope. the 3 1/2" has been in there for a few weeks now. My question on the age is the big one that the pic is of. I.... well Marie caught him last week. I thought that the fish with stripes were juveys. Hes over 8"s. The ear is proportional to his size as to what I see with most gills around here. Maybe a touch smaller. Ive just started the gills here within the past couple months in the tanks. Ive got 5 in there now. I have one that changes colors. Its SOOOO COOOL!

[shooter]

around eight yrs.

[Zig]

JM - I spent a few minutes trying to find some sort of published data on average length/age charts for your area. Came up empty.
Having to fall back on merely the picture and the knowledge that your growth season is longer then what the northern tier is.....................and knowing the age class from fish recenty sampled from a year round warmwater environment here that may mirror the growth season there..............................if a guess was to be given, I'd check the 3 year old box with an eraser mark in the 4 year box.
This is merely a guess (read: opinion). Your mileage may vary.

One thought about "catching the 3½ with multiple minnows hanging out of his mouth" - was this just after the minnows were added to the tank?
All the BG I've ever kept did one thing very well - eat. When "other" food sources weren't available they would turn to the smaller fish in the tanks. The only other time I noticed a distinct usage of smaller fish was directly after they were added to an established tank.
Bluegill are very territorial in captivity and easily conditioned - meaning they will try consuming anything if it is presented to them that same way a food source was previously - either from feeding conditioning or sheer irritation of something else entering their "space".

[Jeremy R. Mayo]

Ima go with irritation. Most of the time they just kinda school around in the tank. Something will set the bass off and they all go nuts chasing after the minnows. The lil guy kinda hangs out underneath a big log ive got in there. I think hes scared of the bigger fish and them pushin him around. Although Ive seen all the fish layed together. Kinda funny lookin at a bass and a few gills just hangin out with each other. Maybe the lil guy is just takin advantage of an easy grab of food so he doesnt have to get out and about with the rest of the fish.

Thanks for ageing that fish. I was gonna guess 2 maybe 3. I was pretty close.