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

Migratory fishes with periodic life history strategies are sensitive to river regulation. Populations of these may persist in highly regulated rivers by using tributaries that provide access intermittently connected spawning and early stage habitat floodplains. We analyzed system hydrology associated movement a long-lived strategist, the alligator gar ( Atractosteus spatula), Brazos River, Texas. hypothesized (1) flow regulation on mainstem has resulted reduction flood pulses, but have been less altered (2) migrate into during high flows temperatures. Our analysis revealed pulses were reduced not an adjacent, tributary where floodplain-inundating now outnumber those mainstem. Using data from tagged fish, we derived statistical models predicting greater occurrence when water temperature exceeded 25 °C discharge 400 cubic meters per second. These results emphasize can mitigate impacts populations gar.