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

espanolSe investigaron las condiciones oceanograficas que podrian influir en la riqueza y distribucion de mamiferos marinos en costas del Pacifico Central Mexicano durante el 2011. Las observaciones de mamiferos marinos se realizaron desde dos plataformas de investigacion. Se muestrearon mensualmente 6 estaciones, donde se realizaron lances de CTD hasta 100 m y se tomaron muestras de agua para determinacion de nutrientes inorganicos; y otras 15 estaciones fueron muestreadas solamente durante invierno en una region mas amplia. Se utilizaron imagenes de satelite (MODIS-AQUA L2) para obtener valores de temperatura superficial del mar (TSM) y clorofila (Chl-a); y datos de altimetria para identificar estructuras dinamicas de mesoescala en la region. Durante invierno-primavera se encontraron valores altos de salinidad (34,6), valores bajos de nitratos y nitritos (~3-4 µM), silicatos (5-7 µM) y clorofila (~10 mg m-3); como tambien valores bajos de temperatura (~23,5°C) y la presencia de giros ciclonicos cerca de la costa. Esto coincidio con la riqueza mayor (de 5 a 9 especies dependiendo la escala espacial) de mamiferos marinos en la zona. La especie dominante fue Megaptera novaeangliae (0,092 avistamientos km-1), la cual se distribuyo hacia zonas costeras en aguas someras. Durante verano-otono se registraron valores bajos de salinidad (32,8) y Chl-a (0,1 mg m-3). Se detecto una disponibilidad alta de fosfatos (2,5 µM), la presencia de giros anticiclonicos y temperaturas altas (~31°C), coincidiendo con la riqueza mas baja (3 especies) de mamiferos marinos. Stenella attenuata fue la especie dominante (0,036 avistamientos km-1), cuyos individuos fueron encontrados distribuidos cerca de las costas de Jalisco y Colima (0-3mn), en aguas someras con una disponibilidad alta de nutrientes inorganicos. El analisis de componentes principales mostro que la batimetria (99.6%) fue el principal parametro que explica la varianza de los datos, por lo que podria potencialmente modular aspectos ecologicos de los mamiferos marinos. EnglishThe oceanographic conditions that could influence richness and distribution of marine mammal species in the coastal area of the Mexican Central Pacific (MCP) were investigated throughout 2011. Marine mammals observations were obtained from two research platforms. CTD casts were deployed down to 100 m, water samples were taken monthly at six stations for determination of organic nutrients, and another 15 stations were sampled over a wider area only during the winter. Satellite images from MODIS-AQUA L2 were used to obtain sea surface temperature (SST) and chlorophyll-a (Chl-a) values, likewise altimetry data to identify mesoscale dynamic structures in the region. High salinity values (34.6), low concentrations of nitrates and nitrites (~3-4 µM), silicates (5-7 µM), Chl-a (~10 mg m-3), and low SST (~23.5°C) were detected, as well as the presence of cyclonic gyres near the coast during the winter-spring period. This coincided with high marine mammal species richness in the area (from 5 to 9 species depending on spatial scale). The dominant species was Megaptera novaeangliae (0.092 sightings km-1), which was distributed close to the coast in shallow waters. Low salinity (32.8) and Chl-a values (0.1 mg m-3) were detected during the summer-fall period. High phosphate availability (2.5 µM), presence of anticyclonic gyres, and high SST (~31°C) were also found, coinciding with low species richness (3 species). The dominant species was Stenella attenuata (0.036 sightings km-1); those individuals were found distributed near the Jalisco-Colima coast (0-3 nm) in shallow waters with high inorganic nutrient availability. The principal components analysis showed that bathymetry (99.6%) was the main parameter explaining data variance; this parameter could therefore potentially modulate ecological aspects of marine mammals.