New Zealand Journal of Marine and Freshwater Research abstracts

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Mortality estimates for the rock lobster, Jasus edwardsii, near Gisborne, New Zealand

John H. Annala

Fisheries Research Division, Ministry of Agriculture and Fisheries, P.O. Box 19062, Wellington, New Zealand

Abstract The instantaneous total (Z) and fishing (F) mortality rates were estimated for the New Zealand rock lobster, Jasus edwardsii (Hutton), along the east coast of the North Island from the Wairoa River to East Cape. Estimates of Z were made from the seasonal size-frequency distributions (SFDs) of rock lobsters landed from five separate fishing areas for up to five fishing seasons using three different methods. Z and F were also estimated from the rate of return of tagged rock lobsters released in four of the five areas. The best estimates of Z and F for each area were considered to be estimates of F based on tag returns grouped quarterly and taken over an 8 or 9 month fishing season; estimates of Z based on these estimates of F from tag returns, with the addition of an assumed value for the annual instantaneous natural mortality rate of 0.10; and estimates of Z from the SFD analyses. These estimates were more consistent with the estimated lifespans in the fishery than were the estimates of Z derived from tag returns.

Keywords Jasus edwardsii; Crustacea; tagging; size-frequency distributions; mortality estimates; Gisborne, New Zealand.

New Zealand Journal of Marine & Freshwater Research, 1980, 14(4): 357-371
Received 21 May 1980; revision received 15 September 1980 Fisheries Research Division Publication 419

PDF file of entire paper: medium quality (913K); (scanned from paper original: notes about this process)

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