MEPS 218:153-166 (2001)  -  doi:10.3354/meps218153

ABSTRACT: Settlement and recruitment of the sea urchin Evechinus chloroticus was determined by a series of field and laboratory experiments on the South Island of New Zealand. Using settlement samplers, we monitored settlement of larvae at 1 to 2 mo intervals during 1992, 1993 and 1994. Recruitment over the same period was monitored from 3 to 8 mo intervals by quantifying both the density and percentage in the population of recruits (juveniles <20 mm test diameter). Settlement and recruitment were higher in Doubtful Sound (SE South Island) than in Tory Channel (NE South Island). For Doubtful Sound, a large settlement between August 1992 and February 1993 (up to 1.14 settlers sampler^-1 d^-1) was followed by an increase in recruit density from 2.1 to 13.8 recruits 20 m^-2 during the subsequent 9 mo (November 1992 to August 1993). Settlement during the following 2 yr was lower (<0.12 sampler^-1 d^-1), during which time the density of recruits decreased from 13.8 to 2.1 recruits 20 m^-2. A similar pattern was found in Tory Channel where a lower settlement intensity was observed in 1992 (<0.05 sampler^-1 d^-1) and the density of recruits over the following year was less than 0.6 individuals 20 m^-2. In 1993, settlement was up 10-fold to 0.54 recruits sampler^-1 d^-1, and the density of recruits increased from 0.3 to 5.0 juveniles 20 m^-2 during the following 5 mo. The correlation between settlement and recruitment is described by the linear relationship, y = 1.4 + 0.14x, where y = annual recruitment (individuals <20 mm TD 20 m^-2) and x = annual settlement (total number of settlers on samplers). Settlement and metamorphosis behavior of competent larvae was examined in the laboratory. Larvae show a preference for natural substrates (i.e. Coralline algae >oyster shell > aged rock > aged plastic) and for surfaces with older biofilms. Given the findings of the current research, settlement samplers may be one tool that can increase our understanding of relative settlement intensity and other recruitment processes in E. chloroticus, and aid in the sustainable management of this species.

KEY WORDS: Evechinus chloroticus · Echinoid · Settlement · Recruitment · Larvae · Population dynamics · Fisheries