Tag retention, growth, and survival of age-0 Alligator Gar following surgical implantation of acoustic transmitters

Objectives Restoration efforts for Alligator Gar Atractosteus spatula include stocking programs in multiple states; however, limited efforts have occurred to document poststocking survival. Acoustic telemetry can be used to estimate survival of fish, but age-0 Alligator Gar have not been acoustically tagged previously. Our objectives in this study were to (1) develop a protocol for acoustic transmitter implantation in age-0 Alligator Gar and (2) determine the appropriate size of acoustic transmitter for future field studies by assessing tag retention and posttagging survival and growth of age-0 Alligator Gar in a hatchery setting. Methods A total of 125 age-0 Alligator Gar were equally sorted into five treatment groups: (1) tagged with Innovasea (Halifax, Nova Scotia, Canada) V6-2x dummy tags, (2) tagged with V7-4x dummy tags, (3) tagged with V9-1x dummy tags, (4) sham surgery fish that underwent the entire surgical process but did not have a tag inserted, and (5) control fish that were not anesthetized and were only measured for total length, body width anterior to the pelvic fins, and weight. Following handling and/or surgery, Alligator Gar were monitored in hatchery holding tanks each day for 14 to 15 d postsurgery for evidence of tag shedding, mortality, cannibalism, or other adverse effects. Results During the monitoring period, all tagged Alligator Gar retained the dummy tags, and incisions had completely healed by the end of the trial. We documented three mortalities (n = 2 with V6 tags, n = 1 with a V9 tag), resulting in 4% mortality of fish with transmitters. Based on logistic regression analysis, treatment group, total length, weight, tag burden, or relative condition did not have a significant effect on survival of age-0 Alligator Gar. We also did not detect any significant differences in growth between treatment groups during the monitoring period. Conclusions Our results suggest that short-term tag retention, survival, and growth of age-0 Alligator Gar (∼200–400 mm TL) are not significantly altered by surgical implantation of acoustic transmitters. Both V6 and V7 transmitters would be suitable for use in future studies of Alligator Gar >180 mm TL, while V9 transmitters could be used in Alligator Gar >250 mm TL. The use of acoustic telemetry in future field studies of Alligator Gar will allow researchers and managers to answer key questions related to movements, habitat use, and survival, improving the outcomes of restoration programs throughout the range of the species.