Cephalopod paralarval assemblages in the Gulf of California during 2004-2007

The responses of cephalopod paralarvae to environmental and hydrodynamic variability were analyzed using data collected during 8 oceanographic cruises (2004-2007) carried out in the entire Gulf of California. Redundancy analysis showed that temperature and salinity at 10 m depth (on the first axis), and zooplankton volumes and chlorophyll a concentration (on the second axis) were the main environmental variables influencing paralarval abundance. Relatively high correlations with the first axis were found in paralarvae of Pterygioteuthis hoylei (-0.5126), in the SD complex (Sthenoteuthis oualaniensis and Dosidicus gigas, 0.4526), and in Gonatus pyros (-0.3350). We observed 3 recurrent cephalopod paralarval assemblages related to the seasonal flux of water masses. The Gulf and Shallow assemblages were distributed mostly in Gulf of California water (salinity >= 35.0) located in the most productive environment. The Tropical assemblage was distributed in tropical surface water, associated with high temperatures and a less productive environment. During the spring, species richness and diversity in the assemblages were high in response to northward advection of tropical surface water into the gulf. The lowest richness values were recorded during summer, associated with the southward flow of Gulf of California water, and the highest temperatures of the year. The assemblages included mostly pelagic, tropical-subtropical taxa and few temperate and cosmopolitan taxa. Paralarval abundance in the gulf was numerically dominated by a few species, but each assemblage had a significantly different community structure and seasonal latitudinal boundaries, suggesting assemblages can be used as biological indicators of the distribution of water masses in the gulf.