DISTRIBUTION AND ABUNDANCE OF TWO IMPERILED GRAPTEMYS SPECIES OF THE PASCAGOULA RIVER SYSTEM
Species distribution and abundance is often difficult to delineate due to species factors (e. g., crypsis, low abundance) or to researcher sampling techniques. Species of the genus Graptemys are primarily riverine turtles and have historically been subject to declines because of anthropogenic changes to river systems. Therefore, to better inform conservation efforts, we thoroughly studied the distribution and abundance of two imperiled Graptemys species within the Pascagoula River System, Mississippi, USA: the Yellow-blotched Sawback (Graptemys flavimaculata) and the Pascagoula Map Turtle (Graptemys gibbonsi). Turtle populations were studied in 17 counties in southeastern Mississippi using four methods: mark-resight population surveys (three populations), bridge surveys (160 bridge crossings), basking density surveys without marked individuals (23 localities), and trapping (three populations). Graptemys flavimaculata was found to be present throughout its historical range, as well as in new drainage localities; abundance in historically surveyed areas was generally higher than previous surveys had reported. Graptemys gibbonsi was also found in many new localities and occurred in most of the drainages of the Pascagoula River system. However, abundance was much lower for G. gibbonsi than for G. flavimaculata throughout the Pascagoula River system and individuals were not found in several historical localities, suggesting localized extirpations. We recommend that G. gibbonsi should be listed as state Endangered in Mississippi and Louisiana, U. S. federally listed as Threatened, and upgraded to Endangered (EN) under IUCN listing guidelines. Future conservation measures should extend to protect additional riparian habitat throughout the Pascagoula River system and future surveys of other Graptemys species are warranted due to the imperiled status of this genus.