Estimating daily age of catfish using otoliths

Peter C. Sakaris and Elise R. Irwin

Alabama Cooperative Fish and Wildlife Research Unit

Auburn University

Objective

• Assess the effects of hydrology on spawning, hatching success and growth of YOY catfishes in regulated systems

- Daily Aging

Prepositioned Area Electrofishers

• Juveniles catfishes were collected at day and night using PAEs on sand and gravel bars at two mainstem sites and three tributary sites.

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22 28 34 40 46 52 58 64 70 76 82 88

Total Length (mm)

Num

ber

of F

ish

Site: Uphapee CreekDate: 9/17/03N=40

Prepositioned Area Electrofishers

YOY Channel Catfish

< 100 mm

YOY Catfish – Daily AgingOtolith Removal

Use same methods described for adult catfish, with a few exceptions:

1) Use a dissecting scope or a portable lamp with magnification, 2) use a scalpel to cut into the fish, and 3) do not drop the otoliths (a little larger than a grain of salt).

YOY Catfish – Daily AgingOtolith Processing

1) Mount otoliths in CrystalBond mounting wax using a dissecting scope and small dissecting forceps (initially, same as adult otoliths, but on a much smaller scale)

2) Slowly grind to core using 600 grit, fine sandpaper

3) Routinely check otolith using a compound microscope to see if core is visible

4) When core is visible, flip otolith over and slowly grind other side down until you have a thin section

5) Routinely check otolith to see if daily rings are visible

Catfish have daily rings.

Future Work• Refine aging techniques -

- Use finer grit when grinding other side of otolith

Fewer scratches, more polished

-Use alternative mounting material

• Validate the technique using known-age fish

• Apply it to wild fish

Don’t forget the little guys,

ANY QUESTIONS?