Abundance of Flaccisagitta enflata and analysis of Chaetognatha community in a circadian cycle in Bahía Magdalena lagoon system Baja California Sur, Mexico

Abstract

The chaetognath Flaccisagitta enflata abundance was determined in the Bahía Magdalena lagoon complex, Baja California Sur, Mexico. This study is based on two sampling methods, in the first one zooplankton was collected from a basic plan of 28 stations, for eight months in 1982, and the second, during 24-hour cycle, August 1-2 during 1988. The capture of organisms was made with a standard conical net of 0.3 m of mouth diameter, 1 m long, and 0.3 mm of mesh size. Analysis revealed that F. enflata average abundances were low from February to June, and significantly higher from July to December (p<0.05). The results of the 24-hour cycle, showed that the total abundance of chaetognaths and F. enflata follows the same trend with the tidal cycle. However, no significant differences day/night capture (p<0.05) were observed between different species of chaetognaths, except for Parasagitta euneritica, Serratosagitta bierii and Mesosagitta minima. The presence of individuals of F. enflata 2.0 mm (new born) and adults near the mouth of access to the lagoon, were possibly transported from the adjacent oceanic area during the influx of warm waters from August to November.