ESTIMATING THE ANNUAL PROPORTION OF NONSPAWNING ADULTS IN NEW-ZEALANDHOKI, MACRURONUS-NOVAEZELANDIAE

Trawl surveys of hoki, Macruronus novaezelandiae (Hector) in the South land and subantarctic areas (Southern Plateau) of New Zealand's Exclus ive Economic Zone were carried out in May 1992 and 1993. The proportio n of females of each age that would spawn in the coming spawning seaso n (July-August) was estimated on the basis of histological analysis of gonad samples and ageing data. Comparisons were made between numbers of fish at age in these surveys and numbers of fish at age in surveys in November-December 1991 and 1992 to estimate migration before May. T he results indicate that 66% (standard error [SE] of 3%) of females ag e 7 and over that were on the Southern Plateau in May 1992 would spawn in winter 1992, compared with 65% (SE 2%) in 1993. If the number of h oki estimated to have already migrated out of the survey area in May a re included as prespawners, then up to 67% (SE 5%) of adult females we re predicted to spawn in winter 1992 and 82% (SE 3%) in winter 1993. T his study confirms that the proportion of adult hoki that spawn in a g iven year is substantially less than 1. it is not known how much this varies, whether it is with or without trend, or whether it is correlat ed with any environmental variables. Fishery indicators such as stock and fishery risk are particularly sensitive to the annual proportion o f adult hoki that spawn, and it is possible that its variation could o bscure any underlying stock-recruitment relationship.