DOI 10.1007/s00227-006-0574-zRESEARCH ARTICLE Vertical structure of very nearshore larval Wsh assemblages in a temperate rocky coast

Abstract Small-scale vertical patterns of larval distri-bution were studied at a very nearshore larval Wsh assemblage, during the spring–summer period of sev-eral years, at two depth strata (surface and bottom) using sub-surface and bottom trawls. A total of 4,589 larvae (2,016 from surface samples and 2,573 from bot-tom samples) belonging to 62 taxa included in 22 fami-lies were collected. Most larvae belonged to coastal species. Although inter-annual variations in larval den-sity and diversity could be found, total larval abun-dance was always higher near the bottom whereas diversity was higher at the surface. A marked distinc-tion between the structure of surface and bottom assemblages was found. Sixteen taxa explained 95 % of the similarity among surface samples. Larvae which contributed most to this similarity included species like clupeiformes, sparids and serranids, and also blenniids, tripterygiids and some labrids. In the bottom samples, fewer species were present, with only six taxa, almost exclusively from species which lay demersal eggs, con-tributing to 95 % of the similarity between samples. Larvae present at the surface were signiWcantly smaller than at the bottom. For some of the most abundant species found at the bottom, only small larvae occurred at the surface while the whole range of sizes was pres-ent at the bottom, indicating that larvae may be com-pleting the entire pelagic phase near the adults’ habitat. These results indicate that larval retention near the reefs probably occurs for these species, although for others dispersal seems to be the prevailing mechanism