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.

Prepositioned Area Electrofishers YOY Channel Catfish < 100 mm

YOY Catfish – Daily Aging Otolith 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 Aging Otolith 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?