Seasonal changes in depth distribution, sex ratio and size frequency of spiny lobster Jasus edwardsii on a coastal reef in northern New Zealand

Abstract

Overall population size remained relatively stable over a 3 yr study period. Marked differences in density, sex ratio and size frequency of spiny lobsters occurred between depths on the reef over a horizontal scale of 300 m. These differences varied seasonally and were related to moulting, reproductive and feeding cycles. Highest densities of females in shallow (<10 m) water coincided with moulting in May. Males moved inshore only briefly to moult in October-November often with no concomitant increase in male density in shallow (<10 m) water. Increases in density of females at the deep (25 m) seaward edge of the coastal reef occurred during the egg-bearing period. In summer (December, January) the density of large males at a deep patch reef (25-30 m) increased. These males foraged nocturnally for bivalves on the surrounding sand flat. -from Author