JPR Advance Access originally published online on September 8, 2006
Journal of Plankton Research 2006 28(11):1081-1098; doi:10.1093/plankt/fbl040
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Larval fish assemblages and geostrophic circulation in Bahía de La Paz and the surrounding southwestern region of the Gulf of California
1 Centro Interdisciplinario de Ciencias Marinas, Departamento de Plancton y Ecología Marina, Ave. Instituto Politécnico Nacional s/n, CP 23000, La Paz, BCS, México and 2 Centro de Investigación Científica y de Educación Superior de Ensenada km 107 Carretera Tijuana-Ensenada, CP 22860, Ensenada Baja California, México
* Corresponding Author: lsvelasc{at}prodigy.net.mx/lsvelasc{at}ipn.mx
Received April 27, 2006; accepted in principle July 10, 2006; accepted for publication August 31, 2006; published online September 8, 2006
Communicating editor: K.J. Flynn
We analyze spatialtemporal relationship between larval fish assemblages and geostrophic surface flow in Bahía de La Paz and the neighboring Gulf of California (May, July and October 2001 and February 2002). The analysis of fish larvae distribution in relation to geostrophic circulation and hydrography is an innovative interdisciplinary approach for the understanding of fish larvae ecology. The BrayCurtis Index defined two larval fish assemblages with spatialtemporal variations: coastal assemblage dominated by epipelagic coastal species (e.g. Sardinops caeruleus) and oceanic assemblagesoceanic and transitional oceanic assemblages both dominated by mesopelagic species (e.g. Vinciguerria lucetia and Benthosema panamense) but with different larval abundance. The assemblage variations appear to be related to water exchange between the bay and the Gulf through the North Mouth. During JulyOctober, the geostrophic flow through the entrance is strong, and the oceanic assemblages spread in the whole bay, whereas during FebruaryMay when the geostrophic transport is weak, the coastal assemblage is distributed over the whole bay. The strong summerautumn water interchange between bay and gulf is in agreement with the annual evolution of the surface water properties inside the bay, from high-salinity Gulf of California Water during winterspring to fresher Tropical Surface Water during summerautumn, when the highest species number was recorded.