Influence of the oceanographic dynamic in size distribution of cephalopod paralarvae in the southern Mexican Pacific Ocean (rainy seasons 2007 and 2008)

Abstract

ABSTRACT. The southern Mexican Pacific Ocean presents seasonal changes related to the rainy season and Tehuano winds, which generate mesoscale processes affecting biological productivity and marine biodiversity. Size distributions of squid paralarvae collected in this region during the rainy season (July 2007 and May-June 2008) were analyzed in relation to regional oceanography. Samples were collected through oblique hauls, and CTD casts were used to determine the structure of the water column. Between surveyed periods, there were no significant changes in the water temperature at 10 m, but there were significant variations in the mixed layer depth (MLD). The number of taxa, community composition and total abundance of paralarvae were similar between periods. However, in July paralarvae ≤2.0 mm were distributed along the margins of cyclonic and anticyclonic eddies associated with high temperatures. In May-June, the MLD and high concentrations of chlorophyll-a (Chl-a) determined the presence of a group of oceanic paralarvae and another of coastal paralarvae, separated by an upwelling front. The percentage of recently spawned paralarvae (≤2.0) nearly doubled during this period as a result of increased coastal sampling and high concentrations of Chl-a, indicating a coupling of adult reproduction with regional productivity. In the absence of winds, the mesoscale oceanographic complexity generates gradients and a differential effect on the distribution, transport and survival of cephalopod paralarvae.

Seasonal changes in paralarval cephalopod communities on the southwest coast of Baja California Sur (spring and autumn 2003)

“…This species complex is formed by paralarvae, measuring ≤3.0-4.0 mm mantle length (ML), that cannot be morphologically differentiated to species (Staaf et al 2011, De Silva-Dávila 2013. This complex has been positively correlated with high temperatures at the 3 above mentioned regions, despite the different environments, and paralarvae measuring ≤2.0 mm ML evidenced the occurrence of spawning events in all these regions (Granados-Amores et al 2010, De Silva-Dávila 2013, Aceves-Medina et al 2017, exhibiting the reproductive plasticity and opportunistic nature of these species (Hoving et al 2013, Hernández-Muñoz et al 2016.…”

“…En el golfo de California, durante 2004de California, durante -2007, sin influencia significativa de ENOS, 3 asociaciones recurrentes de paralarvas se acoplaron a las masas de agua superficiales, lo que evidencia el transporte de especies tropicales al interior del golfo y el enriquecimiento de la comunidad residente (De Silva-Dávila et al 2015). Por otro lado, en el golfo de Tehuantepec, la distribución de tallas y las comunidades oceánica y costera de paralarvas estuvieron influenciadas por 2 remolinos y un frente de surgencia, así como por la hidrodinámica sobre la plataforma continental (Aceves-Medina et al 2017). La costa suroccidental de Baja California Sur es una de las regiones menos muestreadas de la zona noroeste, por lo que se desconoce, en su mayoría, el efecto estacional de la dinámica oceanográfica en las comunidades de paralarvas.…”

“…Este complejo está formado por paralarvas de estas especies que, a tallas ≤3.0-4.0 mm de longitud de manto (LM), no se pueden diferenciar morfológicamente a nivel de especie (Staaf et al 2011, De Silva-Dávila 2013. Este complejo se ha correlacionado positivamente con temperaturas altas en las 3 regiones mencionadas, a pesar de los diferentes ambientes de distribución, y sus paralarvas de tallas ≤2.0 mm LM evidenciaron eventos de desove en todas ellas (Granados-Amores et al 2010, De Silva-Dávila 2013, Aceves-Medina et al 2017, lo cual refleja la plasticidad reproductiva de estas especies y su naturaleza oportunista (Hoving et al 2013, Hernández-Muñoz et al 2016.…”

“…The paralarval community structure from Ensenada, Baja California, to Point Abreojos, Baja California Sur, during the 1997-2001 El Niño/Southern Oscillation (ENSO) event was modulated by physical variables associated with the latitudinal extension and retrieval of water masses, which prompted a significant change in community indexes and in the dominance of species whose biogeographic affinities were associated with anomalous warming or cooling events (Durazo and Baumgartner 2002, Granados-Amores et al 2010). During 2004-2007, when ENSO influence was not significant in the Gulf of California, 3 paralarval assemblages were recurrently found in surface water masses, indicating that tropical species were transported into the gulf and enriched the resident community (De Silva-Dávila et al 2015). On the other hand, size distribution and oceanic and coastal paralarval communities in the Gulf of Tehuantepec were influenced by 2 eddies, an upwelling front, and the hydrodynamics over the continental shelf (Aceves-Medina et al 2017).…”

“…During 2004-2007, when ENSO influence was not significant in the Gulf of California, 3 paralarval assemblages were recurrently found in surface water masses, indicating that tropical species were transported into the gulf and enriched the resident community (De Silva-Dávila et al 2015). On the other hand, size distribution and oceanic and coastal paralarval communities in the Gulf of Tehuantepec were influenced by 2 eddies, an upwelling front, and the hydrodynamics over the continental shelf (Aceves-Medina et al 2017). The southwestern coast of Baja California Sur is one of the least studied regions in northwestern Mexico; thus, the seasonal effect of ocean dynamics on paralarval communities there is mostly unknown.…”