Long-Term Trends in Ringed Sawback (Graptemys oculifera) Growth, Survivorship, Sex Ratios, and Population Sizes in the Pearl River, Mississippi

Abstract

Effective management of long-lived species requires demographic and life-history data that are best acquired from long-term studies. The ringed sawback (Graptemys oculifera), endemic to the Pearl River watershed of Mississippi and Louisiana, is a species of management concern at both the state and federal levels. Population sizes, trapping success, basking counts, sex ratios, survivorship, and growth of this species were investigated at 5 sites on the Pearl River in Mississippi over a 25-yr period. Estimates of age at maturity were 4.6 yrs for males and 9.1 yrs for females. Mean annual survivorship estimates for males, females, and juveniles were 0.88, 0.93, and 0.69, respectively. Maximum longevity estimates were 48.8 yrs for males and 76.4 yrs for females. Average longevity estimates were 8.5 yrs for males and 13.9 yrs for females. The sex ratio of captured turtles was male-biased before 2000 but unbiased after 2000. Realized population growth estimates indicated that 4 populations were stable over the 25-yr period and 1 population had declined. Population estimates and basking counts trended downward through time at most sites. Trapping success after 2000 for all sites combined declined by 77%, 45%, and 25% for juveniles, males, and females, respectively. Taken together, these data indicate that 1 population of G. oculifera has declined, 3 appear to be in the initial stages of decline, and 1 is relatively stable. Additional monitoring of these populations will be necessary to determine if these trends continue into the future.