HR: 1400h
AN: OS53A-13    [Abstracts]
TI: Larval Fish Assemblages and Geostrophic Circulation in Bahía de La Paz and the Surrounding Southwestern Region of the Gulf of California.
AU: * Sanchez-Velasco, L M
EM: lsvelasc@ipn.mx
AF: CICIMAR, Ave. Instituto Politecnico Nacional s/n, La Paz, BCS 23000, Mexico
AU: Beier, E
EM: ebeier@cicese.mx
AF: CICESE Campus La Paz, Miraflores 334 entre Mulege y La paz, La Paz, BCS 23050, Mexico
AU: Lavín, M F
EM: mlavin@cicese.mx
AF: CICESE, km 107 carretera Tijuana-Ensenada, Ensenada, BC 22860, Mexico
AU: Avalos, C
AF: CICIMAR, Ave. Instituto Politecnico Nacional s/n, La Paz, BCS 23000, Mexico
AB: Using hydrographic data and zooplankton samples from four oceanographic cruises during May, July and October 2001 and February 2002, we analyze the relationship between larval fish assemblages and geostrophic flows in Bahía de La Paz and the neighbouring Southwest Gulf of California. The analysis of fish larvae distribution linked to geostrophic circulation is an innovative interdisciplinary approach for the understanding of fish larvae ecology. The Bray-Curtis Dissimilarity Index defined two types of larval fish assemblages with seasonal variations: 1) The Coastal assemblage which was dominated by epipelagic coastal species like Sardinops caeruleus, Ophistonema spp. and 2). The Oceanic assemblages: Oceanic and Transitional-Oceanic assemblages, both dominated by mesopelagic species like Vinciguerria lucetia, Diogenichthys laternatus, Benthosema panamense but with different relative larval abundance and frequency of occurrence. The seasonal variations of the assemblages inside Bahía de La Paz appear to be related to the water exchanges between the bay and the Gulf of California. During July and October the geostrophic flow through the North Mouth is strong and as consequence, the Transitional-Oceanic assemblage cover practically the whole bay, while during February and May, when the geostrophic transport through the North Mouth is weak, the Coastal assemblage spreads over the whole bay. Results show that the spatial distribution of larval fish assemblages during the sampled periods is linked with the patterns of geostrophic circulation. This suggests that large amounts of fish larvae are transported by geostrophic flow, rather than by the total currents (Ekman plus geostrophic). The cyclonic geostrophic pattern of circulation during the warm period was also detected with direct observations of velocities from June to October of 2004.
DE: 4512 Currents
DE: 4890 Zooplankton
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly