Reproduction of the sea urchin Loxechinus albus across a bathymetric gradient in the Chilean Inland Sea

The reported bathymetric distribution of commercial sea urchin species varies globally from the intertidal zone down to a depth of a hundred meters or more, although few studies have been conducted at depths >25 m. Urchins that inhabit shallow sites are expected to have access to more food and to display greater gonad development than those from deeper habitats. The latter could, however, play an important reproductive role by enhancing the resilience of the exploited populations. The objective of this study was to verify the existence of deep reproductively active patches of the edible sea urchin Loxechinus albus in two fishing areas of the Chilean Inland Sea, and compare the main reproductive features of these patches over the 0-100 m bathymetric gradients. We evaluated the gonadic index (GI) and KCl-induced spawning in adult L. albus collected between the surface and 100 m depth between September 2008 and March 2009. Urchins were relatively abundant up to 15 m depth, few to 60 m depth and only one patch of urchins was found between 60 and 100 m depth. Asynchrony was observed in the GI and induced spawning between strata and sampling areas, suggesting that urchins located between 30 and 100 m may be reproductively active and may asynchronously spawn during the breeding season, although their potential contribution to the population dynamic is unknown. Future studies should examine the role of the scarce deep-water aggregations for the regional population dynamics of L. albus, in particular in areas where shallow populations have been heavily fished.