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

Abstract

A. We recorded seasonal changes in the paralarval cephalopod communities collected off the southwestern coast of Baja California Sur, Mexico, during 2003. Simultaneous surface and oblique trawls were carried out with CalCOFI-type nets and CTD casts during spring and autumn 2003 on board the R/V Río Suchiate (Secretaría de Marina), at 85 sampling stations (Magdalena Bay to Cape San Lucas). The paralarval cephalopod community predominantly showed tropical affinity in both seasons. During autumn, 11 tropical taxa, 2 cosmopolitan taxa, and one temperate taxon were incorporated to the paralarval community recorded previously in spring and were associated with the decrease in Subarctic Water and the entrance of warm water masses to the study region, modifying the community indexes between seasons. The canonical correspondence analysis showed 2 groups significantly correlated with chlorophyll a concentrations and zooplankton volumes. Oblique tows provide better information on the paralarval cephalopod community, while surface tows can be an efficient method for monitoring and evaluating the hatching areas of the jumbo Pacific squid Dosidicus gigas through their paralarvae, which are included in the Sthenoteuthis oualaniensis-Dosidicus gigas complex (SD complex).Key words: paralarvae, community structure, SD complex, Baja California Sur. R .Se registró el cambio estacional en las comunidades de paralarvas de cefalópodos recolectadas frente a la costa suroccidental de Baja California Sur, México, durante 2003. Para lo anterior, se realizaron arrastres superficiales y oblicuos simultáneos con redes tipo CalCOFI y lances de CTD en 85 estaciones de muestreo (de bahía Magdalena a cabo San Lucas) durante primavera y otoño de 2003 a bordo del B/I Río Suchiate (Secretaría de Marina). La comunidad de paralarvas de cefalópodos fue mayormente tropical en ambas temporadas. Durante el otoño se adicionaron 11 taxones tropicales, 2 cosmopolitas y 1 templado a la comunidad registrada previamente en primavera, todos relacionados con la disminución de Agua Subártica y el ingreso de masas de agua cálida a la región; esto modificó los índices comunitarios entre las temporadas. El análisis de correspondencia canónica mostró la formación de 2 grupos correlacionados significativamente con la concentración de clorofila a y el volumen de zooplancton. Los arrastres oblicuos dan mayor información sobre la comunidad de paralarvas, mientras que los superficiales resultan eficientes para el seguimiento y la evaluación de las áreas de eclosión del calamar gigante del Pacífico, Dosidicus gigas, a través de sus paralarvas incluidas en el complejo Sthenoteuthis oualaniensis-Dosidicus gigas (complejo SD).Palabras clave: paralarvas, estructura de la comunidad, complejo SD, Baja California Sur.

Ommastrephid squid paralarvae potential nursery habitat in the tropical-subtropical convergence off Mexico

“…In Mexico, as in most Latin American countries, oceanographic cruises are organized by independent research groups mostly without continuity in the records of paralarvae and environmental variables. Paralarvae are frequently collected in zooplankton trawls, but typically in very low numbers (Aceves-Medina et al, 2017;Camarillo-Coop et al , 2010;De Silva-Davila et al , 2015;Garcia-Guillen et al, 2018;Ramos et al , 2017;Ruvalcaba-Aroche et al , 2018. Therefore, the modeling of nursery habitat is subject to biases given the discontinuity of field sampling in time and space, and the inherent nature of the over-dispersed abundance data.…”

“…Bibliographic research on SD complex paralarvae presence in the study area was made to compare the GAM output with historical data. Most of the bibliographic data correspond to areas outside the main sampled area, along the Pacific coast of Baja California Peninsula (Camarillo-Coop et al , 2010;Ramos et al, 2017;Palomares-Garcia et al , 2018;Garcia-Guillen et al , 2018;Molina-Arenas, 2018).…”

“…Although the area of the potential nursery habitat reached its maximum extent, the expected abundance of SD complex paralarvae was low in most of the area of study. Journal Pre-proofs Ramos et al , 2017;Garcia-Guillen et al , 2018;Molina-Arenas, 2018 ;Palomares-Garcia et al , 2018).…”