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Welcome to the technical sessions schedule for the 2015 SEAFWA Annual Meeting.

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Tuesday, November 3 • 2:00pm - 2:20pm
Inducing a Check in Age-0 Alligator Gar

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Richard A. Snow, Oklahoma Department of Wildlife Conservation; James M. Long, U.S. Geological Survey, Oklahoma Cooperative Fish and Wildlife Research Unit, Oklahoma State University

Accurate age and growth information is essential for a complete knowledge of life history, growth rates, age at sexual maturity, and average life span in fishes. Alligator gar is becoming increasingly managed throughout its range and because this species spawns in backwater flooded areas, their offspring are prone to stranding in areas with limited prey, potentially affecting their growth. Because fish growth is tightly linked with otolith growth and annulus formation, the ability to discern marks not indicative of annuli (age checks) in alligator gar would give mangers some insight when estimating ages. Previous studies have suggested that checks are often present prior to the first annulus in otoliths of alligator gar, affecting age estimates. We investigated check formation in otoliths of alligator gar in relation to growth and food availability. Sixteen age-0 alligator gar were marked with OTC to give a reference point and divided equitably into two groups: a control group with abundant prey and an experimental group with limited prey. The experimental group was given 2 g of food per week for 20 days and then given the same prey availability as the control group for the next 20 days. After 40 days, the gar were measured, sacrificed, and their sagittae removed to determine if checks were present and how daily age estimates differed. None of the alligator gar in the control group showed checks and their growth was consistent. However, checks were visible on 14 of the 16 otoliths in the experimental group along with low growth during the first 20 days when prey was limited and accelerated growth after prey availability was increased. Age estimates of fish in the control group were more accurate than those in the experimental group, showing that fish growth as a function of prey availability likely induced the checks by compressing daily ring formation. Whether environmental factors other than prey availability similarly affect check formation is an area in need of study.

Tuesday November 3, 2015 2:00pm - 2:20pm EST

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