A new study on age and growth of kingklipGenypterus capensisoff the south and west coasts of South Africa, with comments on its use for stock identification

Abstract

A new study on age and growth of kingklip Genypterus capensis is described. Whole and sectioned otoliths were used to determine the age of kingklip and the three-parameter Von Bertalanffy model to describe and compare growth. Greater availability and wider distribution of samples of larger fish, obtained from the demersal longline fishery, and more robust and advanced statistical analyses, have resulted in improved estimates of kingklip age and growth. Kingklip are relatively slow-growing and long-lived. Males on the South Coast (L ∞ = 130,1 cm; K = 0,149) attain larger size than males on the West Coast (L ∞ = 125,4 cm; K = 0,148). Female kingklip reach a greater size than males on either coast, though those on the West Coast (L ∞ = 132,9 cm; K = 0,135) have a slower growth rate and shorter maximum theoretical length than those on the South Coast (L ∞ = 141,5 cm; K = 0,138). The length : weight ratio of kingklip on the West Coast is greater than for fish on the South Coast. Differences in the growth rate and length: weight ratio between kingklip on each coast are not considered characteristic of discrete stocks or sufficient evidence alone to discriminate between stocks. Until other evidence of stock differences become apparent, the kingklip resource on the South African coast should be considered a single stock.