A Strategy for Increasing Gill-Net Catch Rates and Minimizing Sampling Mortality of Alligator Gars

Abstract

Management of the Alligator Gar Atractosteus spatula has been hampered by the lack of sampling methods that can efficiently reveal population characteristics or minimize incidental sampling mortality. In a 3-year evaluation of the Alligator Gar population in Choke Canyon Reservoir, Texas, we documented changes in sampling methodology that produced an eightfold increase in multifilament gill-net catch rates (from 0.66 to 5.10 fish/h). The increased sampling efficiency was attributed to the development of an aggressive-predator sampling strategy over the study period; our highest catch rates were achieved by (1) observing surfacing fish before net deployment and (2) relocating to a new sampling site when catch rates were less than 1 fish/h. This aggressive strategy resulted in shorter net soak times, which reduced incidental net mortalities; nets soaking less than 30 min produced zero mortalities. Our results suggest that the aggressive-predator strategy is suitable for the majority of Alligator Gar sampling objectives (e.g., collection for age and growth and mark–recapture), which will improve the ability to manage Alligator Gar populations.

Received August 18, 2014; accepted February 4, 2015

ACKNOWLEDGMENTS

We thank the many staff from the Texas Parks and Wildlife Department–Inland Fisheries Division's Heart of the Hills Fisheries Science Center and District 1E for assistance with field data collection. Constructive comments provided by Nate Smith and Michael Baird greatly improved this manuscript. This study was supported by Federal Aid in Sport Fish Restoration grants F-231-R and F-221-M to the Texas Parks and Wildlife Department, Inland Fisheries Division.