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

Aspects of the biology of Raja wallacei and R. pullopunctata were investiga ted using data collected in 1995 and 1996 from research and commercial traw ls on the Agulhas Bank, South Africa. Age and growth parameters were invest igated by examination of bands on the vertebral centrum. Estimates of Von B ertalanffy parameters for R. wallacei were L-infinity = 405.40 mm disc widt h (DW), K = 0.27 and t(0) = -0.08 years for males and L-infinity = 435.23 m m DW, K = 0.26 and t(0) = -0.21 years for females. For R. pullopunctata, th e estimates were L-infinity = 770.50 mm DW, K = 0.10 and t(0) = -2.37 years for males and L-infinity = 1 326.75 mm DW, K = 0.05 and t(0) = -2.20 years for females. Growth was significantly different between sexes for both spe cies. The oldest aged R. wallacei and R. pullopunctata were 15 and 18 years respectively. The length at first maturity was approximately 350 mm DW or 7 years of age for R. wallacei and 600 mm DW or 9 years of age far R. pullo punctata. The length-at-50% maturity for R. wallacei was 395 mm DW for male s and 400 mm DW 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 freq uency of occurrence and volume of prey.