Temporal and alongshore distribution of decapod larvae in the oceanic island of Gran Canaria (NW Africa)

Abstract

Larval transport strongly influences neritic populations of oceanic islands. We investigated the spatial-temporal variability of the assemblage of decapod larvae at the shelf edge off Gran Canaria Island. Environmental and planktonic monitoring were conducted weekly from January to July 2001, at three stations located at different positions in relation to the Trade winds and Canary Current. A total of 5969 decapod larvae of 112 different taxa were recorded. Temporal distribution of decapod larvae abundance displayed two main peaks: the first one took place during February–March associated with the mesozooplankton increase and the second in June–July related to a rise in temperature. The spatial distribution of larvae had a windward–leeward pattern. Larval abundances were much higher in the area of the weak flow around the stagnation point upstream of the island and the warm lee region downstream and were dominated by the benthic species: Galathea intermedia, Philocheras bispinosus, Anapagurus spp., Nanocassiope melanodactyla and Xantho spp. In contrast, on the flank of the island where the current and winds increase, abundances decreased notably with a higher contribution of holopelagic species, such as Gennadas spp. and Deosergestes henseni, suggesting a greater influence of the open ocean waters. Oceanographic conditions related to the island mass effect seems to control the retention zones for decapod larvae. The stagnation point and the lee of the island clearly favour the maintenance of the larval pool nearshore and the self-recruitment in the neritic populations. Consequently, these areas should be taken into account when establishing marine protected areas around oceanic islands