Arquipélago de Alcatrazes (24º06'S, 45º42'W) is 36 km off the coast and it is an Ecological Station since 1987. It is also located near the port region of São Sebastião, São Paulo, hence subjected to introduction of exotic species. Forty samples were taken in the principal island of the archipelago to detect possible introductions. Fifteen samples were from Baía do Oratório and 25 from Saco do Funil. Twenty four species distributed in seven families were found. Only five of them were classified as native, four are Atlantic but cryptogenic in the region because of the disjunct distribution; five are cryptogenic with world wide distribution; and one is a certain introduction, Ciona intestinalis (Linnaeus, 1767). There are other nine species that were not identified, a few of them possibly new species. The presence of one introduced species and the high number of cryptogenic species with strong evidence of introduction indicate that the islands are threatened by non-native fauna. The conservation of the Archipelago demands consideration of the port as one source of stress and the control of exotic species as an important aspect of the management procedures.
Urochordata; taxonomy; bioinvason; geographical distribution; Ciona intestinalis
