Abstract
A monitoring programme was established to collect plankton samples and information of environmental variables over the shelf off the island of Gran Canaria during 2005 and 2006. It produced a detailed snapshot of the composition and seasonal assemblages of the decapod larvae community in this locality, in the subtropical waters of the Canary Islands (NE Atlantic), where information about crustacean phenology has been poorly studied. The larval community was mainly composed of benthic taxa, but the contribution of pelagic taxa was also significant. Infraorders Anomura (33.4%) and Caridea (32.8%) accounted for more than half the total collected larvae. High diversity, relatively low larval abundance throughout the year and weak seasonality characterized the annual cycle. However, in relation to the temporal dynamics of temperature, two distinct larval assemblages (cold and warm) were identified that correspond to periods of mixing and stratification of the water column. The results also indicate that larval release times and durations in the subtropical waters are earlier and longer than at other higher latitudes in the NE Atlantic. We detected the presence of larvae of six species that have not yet been reported from the Canary Islands (Pandalina brevirostris, Processa edulis, Necallianasa truncata, Parapenaeus longirostris, Crangon crangon, Nematopagurus longicornis). Finally, this study provides a baseline for future comparisons with respect to fishery pressure and climate variability in this subtropical region.
Highlights
A key component for ecosystem and fishery management is an understanding of the reproductive strategies adopted by crustacean decapods in response to physical and biological processes
The annual cycle of decapod larvae in temperate waters of NE Atlantic is related to the temperature regime, and seems to be linked to phytoplankton blooms (Kirby et al 2008), with two main abundance peaks during spring and summer (Highfield et al 2010, Pan et al 2011)
It is important to study the current state of decapod larvae assemblages in order to predict and/or detect changes in their population dynamics due to a future warming scenario in the tropics and subtropics. For this reason, using an intensive sampling monitoring off Gran Canaria, we describe here for the first time the seasonal assemblage of the decapod larvae community and associated environmental variables at the Canary Islands
Summary
A key component for ecosystem and fishery management is an understanding of the reproductive strategies adopted by crustacean decapods in response to physical and biological processes. Most decapods have complex life cycles in which they release larvae into the water column where, as plankton, they develop through larval stages and may be transported far from their parental populations or retained near them by specific oceanographic features and larval behaviour (Shanks 1995, Queiroga and Blanton 2005, Jones et al 2007). Many species have evolved elaborate behavioural and life history strategies that exploit favourable periods of the year (those best matching optimal niche requirements) for growth, and minimize exposure of sensitive larval stages to stressful conditions (Ji et al 2010). It is expected that the higher and more stable temperature throughout the year in lower latitudes favours continuous reproduction (Bauer 1992), leading to a weaker seasonality of decapod larvae in the plankton
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