Growth, age structure, and productivity of ling, Genypterus blacodes (Ophidiidae), in New Zealand waters

Abstract

Growth of ling, Genypterus blacodes, from four areas around southern New Zealand (West Coast South Island, Chatham Rise, Southern Plateau, Bounty Platform) was determined by counting rings in otoliths. This aging method was validated by using the progression of modal peaks in length frequencies and by analysing the changing state of otolith margins over 1 year. Calculated von Bertalanffy parameters showed that females grew significantly faster than males in all areas, and that growth rates were significantly different between areas. Ling grew fastest off the West Coast and slowest on the Southern Plateau. Instantaneous natural mortality is in the range 0.17–0.20, and instantaneous fishing mortality is < 0.1 in all areas. Differences in growth rates, length‐frequency distributions, sex ratios, and ages at recruitment indicate that gene flow between areas is probably slight, so there is justification for managing ling as several stocks. © The Royal Society of New Zealand 1993.