Fish larvae and zooplankton biomass around Faial Island (Azores archipelago). A preliminary study of species occurrence and relative abundance.

Abstract

Plankton hauls were conducted off Faial island (Azores archipelago, NE Atlantic), to a depth of 100 m, between February and June 1998, covering the spawning period of a number of commercially important fish species. Seventy-three fish larvae taxa were identified, of which 51 were quantified, one of them a new record for the region, Glossanodon leioglossus (Valenciennes, 1848). The fish larvae community was dominated by mesopelagic and bathypelagic elements (namely Myctophidae and Gonostomatidae), a typical oceanic island environment composition. Total zooplankton showed a biomass peak in May that could correspond to the Spring “bloom”. However, the fish larvae showed an abundance minimum in May and a maximum in June, presenting a general negative relationship with zooplankton biomass and indicating a temporal asynchrony between their annual cycles of production. The comparison of fish larvae abundance with those of other NE Atlantic regions suggests that the zooplankton production in the Azores may be similar to the one found in the Iberian Peninsula continental shelf. Significant spatial density gradients (for fish larvae and zooplankton) were not found with either bathymetry or distance from shore.