Observations on the Captive Biology of the Southern Stingray

Abstract

Complete life history information is essential for effective population management, but little is known about the demographic characteristics of the southern stingray Dasyatis americana. We describe life history characteristics of southern stingrays maintained in captivity from birth to 13 years. Size (disc width [DW]) at maturity ranged from 48 to 52 cm in males and from 75 to 80 cm in females; age at maturity was 3–4 years in males and 5–6 years in females. Individual growth was described using three models: the Gompertz function, von Bertalanffy growth function (VBGF), and logistic function. Analyses of DW at age and weight at age indicated that females were significantly larger at birth and reached larger maximum sizes than males. Because of the ability of the VBGF to fit the observed growth and that of previously reported maximum sizes, we favor its use to describe individual growth dynamics for this species. Using this model, we estimated that for males (n = 20), the asymptotic DW (DW_∞) was 67.4 cm, the von Bertalanffy growth coefficient (k) was 0.44 per year, and the predicted theoretical age at a DW of 0 cm (t ₀) was −0.93 years. The corresponding estimates for females (n = 15) were a DW_∞ of 150.9 cm, a k-value of 0.11 per year, and a t ₀ of −1.61 years. The oldest southern stingrays in the study were a 12-year-old male and a 13-year-old female, and estimates of longevity were 7.9 years for males and 31.5 years for females. The sex ratio of neonates (n = 453) did not differ significantly from 1:1. The life history characteristics derived from captive specimens indicate that southern stingrays are similar to other dasyatids in terms of growth and age at maturity.