New Zealand Journal of Marine and Freshwater Research abstracts

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Yield- and egg-per-recruit analyses for the New Zealand rock lobster, Jasus edwardsii

JOHN H. ANNALA

PAUL A. BREEN

Fisheries Research Centre Ministry of Agriculture and Fisheries P. O. Box 297, Wellington, New Zealand

Abstract The effects of different values of the instantaneous natural (M) and fishing (F) mortality rates and the minimum legal size on the yield- and egg-per-recruit of Jasus edwardsii were estimated for 10 areas around New Zealand. At the current assumed value for M of 0.10, the yield-per-recruit of females \vas insensitive to changes in F or the minimum legal size, whereas the yield-per-recruitof males was maximised at relatively low levels of F and large values for the minimum legal size. Egg-per-recruit (EPR) values varied considerably among areas. The weighted average exploited EPR as a percentage of the unfished EPR for the North and South Islands combined was 27%, and it is not clear if current levels of egg production are sufficient to sustain the population. At the current minimum legal size, a large reduction in F below the current estimated value is required to increase EPR values substantially. Increasing minimum legal size at the current level of F would result in modest increases in EPR. The goals of maximising yield- and egg-per-recruit do not conflict, provided fishing mortality is not reduced below about 0.4.

Keywords New Zealand; rock lobster; Jasus edwardsii; egg-per-recruit; yield-per-recruit; fishery management Received 22 December 1987; accepted 29 March 1988

New Zealand Journal of Marine and Freshwater Research, 1989, Vol. 23: 93-105 0028-8330/89/2301-0093$2.50/0 © Crown copyright 1989 Received 22 December 1987; accepted 29 March 1988

PDF file of entire paper: medium quality (992K); (scanned from paper original: notes about this process)

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