Jasus Edwardsii Larval Recruitment Off the East Coast of New Zealand

Abstract

Geographic differences in levels of Jasus edwardsii puerulus settlement on the east coast of New Zealand during the 1980's were associated with differences in abundance offshore of mid- and late-stage phyllosoma larvae and with water flow patterns. Levels of puerulus settlement on crevice collectors and abundance of phyllosomas in plankton samples were greatest off the North Island south of about East Cape. The pattern of phyllosoma abundance appeared to be determined by factors which included levels of local larval production and the oceanography. Phyllosomas occurred almost exclusively seaward of the continental slope while most pueruli were caught on the shelf. Some phyllosomas reached final stage about 12 months after the spring hatching, but often metamorphosis to the puerulus stage and settlement did not take place until the following summer to spring; this gives an oceanic development period of 12-24 months. Settlement seasons have been generally consistent over time scales of 1-3 decades. Most commonly, settlement is in winter, but the main settlement seasons vary according to locality, nearby sites having similar seasons except over particular stretches of coastline where seasons change radically. Reasons for the seasonal pattern in settlement are unknown. Year to year levels of settlement were correlated at widespread sites, showing that factors which drive larval recruitment may influence large areas in a similar way at the time.