Mesoscale dynamics and yellowfin tuna catches in the Mexican Pacific

Abstract

Catch data of the yellowfin tuna (YFT) fishery were used to study the relationship between the seasonal and spatial variations of YFT with or without the presence of mesoscale structures at the entrance to the Gulf of California (19º–24º N, 104º–112º W). The YFT catches were distributed mainly over the continental shelf and around islands and seamounts. High concentration sets of YFT occurred throughout the year around the Marías islands and Cabo Corrientes, particularly in March and June. A warm (>28ºC) coastal jet with a width of 1.5 Rossby radius (~20.6 km) was observed off Cabo Corrientes during February and April, covering all the continental shelf off Cabo Corrientes. The jet moved at an average speed of 0.31 m s–1 and extended northwards to the Roca Corbetera seamount. The interaction with cooler water generated a frontal zone around which the YFT catches were concentrated. In contrast, during March the wind field was more favorable for the development of coastal upwelling off Cabo Corrientes. We observed an upwelling region with sea surface temperature of 18ºC and an offshore width of about a 3.7 Rossby radius of cold water that covered some 2600 km2. The YFT catches occurred in warmer water north of the upwelling zone.

Influence of coastal upwelling−downwelling variability on tropical euphausiid abundance and community structure in the inshore Mexican central Pacific

“…The interaction of northwestern winds, coastline orientation, bottom topography, and regional current system induce coastal upwelling−downwelling events along the central Pacific coast of Mexico, commonly known as the Cabo Corrientes region (Roden 1964, Torres-Orozco et al 2005, López Sandoval et al 2009a. In this tropical region, upwelling events typically occur from December to May, and are the main oceanographic processes producing seasonal variability in phytoplankton photosynthetic pigments (Álvarez-Borrego 1983).…”

“…Satellite ocean surface chlorophyll a (chl a) images and in situ chl a concentration measurements show that the coastal region off Cabo Corrientes exhibits strong seasonal variability (López Sandoval et al 2009a,b). Satellite images of sea-surface temperature in the region show that the influence of upwelling events can extend about 46 km along the coast, covering an area of approximately 2586 km 2 (Torres-Orozco et al 2005). The effects of these meso-scale coastal features in Cabo Corrientes on zooplankton have been studied for tropical copepods (Suárez-Morales et al 2000), ichthyoplankton (Franco-Gordo et al 2002, León-Chávez et al 2010, and euphausiids (krill; Sánchez-Osuna & Hendrickx 1983.…”

Oceanographic conditions and marine mammals: identifying a potential relationship in the coastal region of the Mexican Central Pacific

“…2 and 4), which had previously been reported as the main fertilizing processes propagating near the continental shelf (200 m) in this region of the MCP (Salas et al 2006, Pantoja et al 2012. The MDS could have resulted in the lifting/sinking (~20 m) of isotherms, allowing cold-water intrusion towards the surface, as has been described by some authors (e.g., Torres-Orozco et al 2005, Salas et al 2006, López-Sandoval et al 2009). Although gyres could not be clearly identified by AVISO data within the study area (due to the 1/3° data resolution); however, the SST and Chl-a satellite data were useful to identified some of these structures that have been described during the entire year.…”

“…2a-d) is the occurrence of upwelling events such as those that have been reported near Cabo Corrientes during the winter-spring period (Filonov et al 2000, Torres-Orozco et al 2005, Kessler 2006, López-Sandoval et al 2009). The NOAA upwelling index 5 for this period suggests an upwelling event, with cold water being transported by winds and marine currents from the northwest, as has been described by Fiedler & Talley (2006).…”

“…The intensity of MDS in the ocean depends in general on the gravity, density gradients, and wind effort, which produce the re-suspension or sinking of particles and organisms (Linacre et al 2010). This allows the establishment of complex trophic webs that generate availability of potential prey (Torres-Orozco et al 2005), leading to the aggregation of top predators such as marine mammals (Rennie et al 2009). …”