Graptemys is one of the least studied turtle genera in North America. Graptemys oculifera (Ringed Sawback) and Graptemys pearlensis (Pearl Map Turtle) are endemic to the Pearl River system of Mississippi and southeastern Louisiana. We studied both species near Columbia, Mississippi, on the Pearl River via a trapping and basking surveys over two years. Additionally, five sites including Columbia were trapped for 27 years to determine long-term trends in capture success and relative abundance (RA). At the Columbia site, body size distribution was bimodal for G. oculifera and atypically unimodal for G. pearlensis; G. pearlensis body lengths were smaller than museum specimens. Population estimates for G. oculifera at the Columbia site indicate a stable population over 25 years. Long-term RA trends indicated that G. pearlensis was less common than G. oculifera in all periods and at all sites from 1988 to 2013. Trends in long-term capture success for G. oculifera and G. pearlensis were negative at all sites, with significant declines at three sites for both G. oculifera and G. pearlensis. Declines occurred both upstream and downstream of a major reservoir. Therefore, a combination of factors (including altered hydrology, human disturbance, lack of recruitment, excessive sedimentation, impaired water quality, and/or the pet trade) appear to be contributing to declines. Additional conservation and protection is warranted for G. pearlensis, and current protections for G. oculifera should be extended. Future studies should continue at our long-term sites to determine whether population declines persist or whether populations stabilize.