The biology of the skates Raja wallacei and R. pullopunctata (Batoidea : Rajidae) on the Agulhas Bank, South Africa

Aspects of the biology of Raja wallace; and R. puLlopunctata were investigated using data collected in 1995 and 1996 from research and commercial trawls on the Agulhas Bank, South Africa. Age and growth parameters were investigated by examination of bands on the vertebral centrum. Estimates of Von Bertalanffy parameters for R. wallace; were Loo = 405.40 mm disc width (OW), K = 0.27 and to = -0.08 years for males and Loo = 435.23 mm DW, K = 0.26 and to = -0.21 years for females. For R. pullopunctata, the estimates were Loo = 770.50 mm OW, K = 0.10 and to = -2.37 years for males and Loo = 1 326.75 mm OW, K = 0.05 and to = -2.20 years for females. Growth was significantly different between sexes for both species. The oldest aged R. wallace and R.pullopunctata were 15 and 18 years respectively. The length at first maturity was approximately 350 mm OW or 7 years of age for R. wallace and 600 mm OW or 9 years of age for R. pullopunctata. The length-at-50% maturity for R. wallace was 395 mm OW for males and 400 mm OW for females. R. waLlacei fed primarily on benthic teleosts and crustaceans. There were significant differences (p < 0.05) in the diet between research- and commercially caught fish, in terms of percentage frequency of occurrence and volume of prey.