Movements and Macrohabitat Use of Alligator Gar in Relation to a Low Head Lock and Dam System

Abstract

Loss of habitat, targeted removals, and overharvest has contributed to the decline of Alligator Gar Atractosteus spatula. There is agreement among commercial fishers, some recreational anglers, conservationists, and natural resource managers that this species warrants conservation. Appropriate management actions require research to further understand the life history and ecology of Alligator Gar populations. We conducted a movement study of 16 Alligator Gar in the lower Ouachita River, Arkansas–Louisiana, for 1 year using acoustic telemetry. The Alligator Gar were stationary at least 28% of the year. We documented 1,552 movement events during the study. The mean (SD) movement rate during the movement events was 1.13 (0.18) km/h, but it varied among individuals. Only 2 of the 16 Alligator Gar were detected upstream of Felsenthal Dam. The tailwater habitat just below Felsenthal Dam was used heavily by the Alligator Gar. The linear home range was 11.9 (7.1) river kilometers. Due to the hydrology of the system, access to the floodplain is not a hindrance to the lateral movement of Alligator Gar in the Ouachita River. The Felsenthal Dam did seem to hinder longitudinal movement, even though high water allowed the fish to move over and around the dam during spring and early summer. Management plans to rebuild Alligator Gar populations in regulated river systems should consider the negative consequences of barriers to lateral or longitudinal movement.

Tributary streams provide migratory fish with access to floodplain habitats in a regulated river: evidence from alligator gar, Atractosteus spatula

“…Due to loss of floodplain connectivity (Fig. 1b), historical eradication efforts, and overharvest, populations of alligator gar have declined in the Mississippi River basin and many coastal rivers draining into the Gulf of Mexico (Kluender et al 2017;Lochmann et al 2021).…”

“…Recent studies have investigated the movements of alligator gar in lotic systems (Buckmeier et al 2013;Smith et al 2020b). However, these studies have generally focused on longitudinal movement of alligator gar in mainstem rivers with minimal consideration of lateral movement (Buckmeier et al 2013;Wegener et al 2017;Lochmann et al 2021). Current populations of alligator gar are considered stable in Texas and Louisiana, yet mainstem rivers in these regions are just as fragmented as areas within their distribution where declines have occurred (Smith et al 2020b).…”