Mesoscale Cyclonic Eddy and Larval Fish Distribution in the Southern Gulf of California (July 2010)

Mesoscale cyclonic eddy effects on the larval fish distribution in southern Gulf of California during July 2010 were analyzed. CTD data and zooplankton samples collected with a closing-opening net (505 µm), were obtained on two transects that crossed the eddy, and on a transect outside of the mesoscale structure. In the later the thermocline depth was at ~40 m with dominance of Vinciguerria lucetia larvae. Opposite to V. lucetia distribution, Diogenichthys laternatus larvae was the dominant species in the deepest strata. In the area influenced by the cyclonic eddy (~350 m depth and ~60 km diameter) the thermocline was sunk from ~25 m (eddy edge) to ~ 50 m depth (eddy center). The isotherms below the thermocline formed a dome from ~350 m to ~100 m depth in the eddy center. This upwelling coincided with the presence of D. laternatus larvae up to the surface. Compared with the transect outside of the cyclonic eddy, the shoaling of the isotherms inside the eddy produced not only an increase of D. laternatus larvae in the whole water column, also decreased drastically the specific richness.