Reproductive cycle and settlement of Evechinus chloroticus in the SUR 5 fishery

Abstract

Evechinus chloroticus (Kina) are an important commercial species in New Zealand waters, being harvested for their gonads or roe. In southern New Zealand the commercial fishery area (SUR 5) for urchins extends from Slope Point to Ararua Bay with a TACC of 455 tons. Information regarding the reproductive cycle of two sizes (>140mm and 80-100mm) of urchin and larval settlement were gathered from two sea urchin populations (Green Islets and Chalky Sound) in southern Fiordland between May 2006 and March 2007, while working on board a commercial vessel harvesting sea urchins. Urchin reproduction was annual at both sites with gametogenesis beginning in June followed by gamete proliferation and differentiation between July and September. Mature gametes were first observed in October. Gametogenesis was typically asynchronous between sexes with spawning activity varying considerably both between urchin sizes and between sites. There were statistically significant differences in the gonad index (GI) of large and small urchins at each site, with much higher GI present at Green Islets overall. Lantern indices were higher in smaller urchins at each site while gut indices were significantly different between size classes at Green Islets but not at Chalky Sound. Settlement was measured using samplers covered with artificial turf, deployed at 8-10 metres depth. A large pulse of settlement was recorded at Green Islets between September and December 2006, no other settlement was found at other times of the year.

This thesis is a combination of scientific investigation by a student in marine science but also includes my anecdotal observations as a commercial urchin diver in the SUR 5 fishery.