Incorporating numbers harvested in dynamic estimation of yearly recruitment: onshore wind in interannual variation of South Australian rock lobster (Jasus edwardsii)

A method for deriving historical recruitment time-series is presented using annual total weight and total numbers landed and. optionally, effort data. The method is age-based and requires a vector of age-specific mean weights . Average weight of harvested individuals (catch weight divided by numbers) conveys information about size structure and thus about mortality rate and recruitment. Annual recruit numbers and fishing mortality were estimated i n the Northern Zone fishery of South Australian rock lobster (Jasus edwards ii). Estimation accuracy was tested with simulated data sets from an indivi dual-based lobster model for four patterns of recruitment variation. Recrui tment time-series were accurately estimated for all four patterns. In appli cation to the lobster fishery. effort data. in addition to catches by weigh t and number were employed. Model-derived recruitment time series from 1978 -1998 were corroborated by the trend of reported annual numbers of lobsters captured below legal size. The principal outcomes are threefold: (1) catch es by weight and number can yield accurate yearly recruitment estimates: (2 ) a rough 11-year cycle was evident in both recruitment and wind time-serie s, (3) yearly recruitment is correlated with August (mid-winter, the time o f post-larval settlement) western wind strength five to seven years earlier .