Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Determining the age of fish

A friend of mine tells me that the age of any fish can be determined from a single scale, sort of like reading rings on a tree. He says the signs can be seen with a 10X magnification. Are there any experts here that can elaborate on this? What kind of instrument is available to use for this method? Any photos available?

I'd like to add: Where does the scale need to be taken from on the fish? Close to the gills and the lateral line?

I believe the best place to get the scales is above the lateral line and in front of the dorsal fin. You need to take multiple scales because if a scale is lost it will regrow but it won't look right.

If nobody answers the question about the 10X magnification by monday I will check on it for you at school.

The writing is a bit small, but if you zoom you can read it if needed. Pull the scale from the lateral line, as those will give the most accurate aging. Fish from southern climates may be more difficult to age than those from northern climates with distinct reduced growth period(winter). Reading a fish's age via their scale takes practice and is not an exact science. It is not like counting the rings on a tree, more like aging a deer by its tooth wear. It varies by region and even different BOW's.

http://www.pondboss.com/forums/ubbthread...true#Post130605



Aging methods - get the article from Dave and read it. MMorgan is right about scales in the south - it will work but is hard and not accurate without help. Pics are in the article and provided by Dave Willis.



scale



otolith location



whole otolith aging



cracked otolith aging

This is some good stuff. Thanks to all.

I'm thinking about buying some 10X power loops from Forestry Suppliers (They are cheep) and very portable. Being that our lake is located in Michigan is it fair to assume that the scale readings will be fairly easy and the other method will not be necessary?

Our fish species are expected to be mostly:

LMB
YP
BG
Crappy
Northern Pike
Common Carp

Anyone see any complications for aging these species?

I've never used these to age a fish, but they are pretty good quality, and the price is hard to beat:

5-Piece Loupe Set for $3.99


I have several sets of them, and they are every bit as good as the expensive ones we buy at work.

These aren't bad either for the price:

16.5 x Clip-on Loupe for $4.99

Brian Graeb - http://forums.pondboss.com/ubbthreads.ph...p;what=showflat



Striper otoliths....

Sorry for the delay. I had to wait for my crack team of fish agers to return from the field to confirm age assignments.

Here is Jason and Tanner adjusting the otolith image on the computer. We have a camera mounted on a dissecting scope that links to a computer. This system allows us to capture images and perform measurements (e.g., back calculations). Notice the otolith image projected on the screen to the left.



The beauty of this system is that we can project the image onto a screen so that multiple readers can view an otolith simultaneously. Prior to this system we would take turns looking through the scope while trying to describe what we were counting as annuli.


Bob's big striper...





Average striper. 22inches, 4.5lbs.





Big Striper = age 5 (harvested in the middle of 6th growing season).




Average striper = age 3 (harvested in the middle of 4th growing season).

cool stuff.... what exactly is the otolith.

The otolith is essentially the ear bone of the fish.

TMK, a couple of generalities for you.

Scales tend to be more useful in the north country than the south country, so you have a reasonable chance. However, it is still an "art" to age scales or even other structures such as otoliths. One good example of the art: it's usually hard to spot the first annual mark on a bluegill scale. It tends not to be nearly as distinct as the later annual marks.

You will have your best luck aging your fish for the first 3-4 years of life. For older fish, we tend to underestimate true age from scales. The annual marks can get pretty closely spaced, and hard to distinguish. However, you should be able to get some idea of growth rates for your fish for the first several years of life, which is very useful information.

Even in Michigan, if most biologists wanted to know the most accurate ages of a sample of fish (say largemouth bass or walleye up to age 10), they'd likely want to use something like the otoliths.