Marine mammal habitat in Ecuador: Seasonal abundance and environmental distribution

Abstract

Marine mammals in the Eastern Equatorial Pacific play a vital ecological role toward structuring trophic systems and the distribution commercially valuable prey. However, scientific study of their populations within the waters surrounding Ecuador has been only infrequently conducted and largely neglected over the past decade. Our research including six marine mammal surveys will investigate the distribution of marine mammals inhabiting the oceanic areas between the Ecuadorian mainland and around the Galapagos Islands. Visual observers documented marine mammal sightings while aboard the Ecuadorian Navy's Oceanographic Vessel the (B/I) Orion last September/October 2008 and April 2009. The range of different species positively identified as well as the large proportion of sightings that could not be identified to species using current survey methodologies, suggests that the diversity and overall marine mammal abundance within Ecuadorian waters may be much higher than previously suspected. Four more surveys covering similar periods of the year will be conducted over the next two years. Biological patterns in this region are closely tied to physical features. Using satellite data, Palacios (2004) discerned seasonal patterns in the surface concentrations of chlorophyll off the West coast of the Galapagos Islands. Here, upwelling driven productivity (which is initiated by the subsurface derived macronutrients) is enhanced by iron inputs derived from the island platform. The confluence of the Equatorial Undercurrent and Peru Current create an area around the islands where enhanced levels of nutrients are available to the ocean's biology. Palacios' harmonic analysis of ocean color data showed that the seasonal cycle of warming and cooling is associated with the North-South migration of the ITCZ and that ocean color which is related to surface primary productivity follows these seasonal SST patterns. Daniel Palacios identified groups of cetacean species that were often sighted in close proximity and described 3 main habitat types around the islands where these groups were found: upwelling modified, stratified, and near-shore. He defined these habitats using composited data from multiple sensors over 9.28 km spatial resolution and averaged over several years to obtain seasonal climatological pictures of cetacean habitat. I will use ocean color from the NASA's Earth observing sensor MODIS (Moderate Resolution Imaging Spectroradiometer) sensor at the same spatial resolution but averaged over days to weeks of time in order to look at more temporally variable processes. Additionally, it may be possible to identify frontal boundaries based on changes in surface chlorophyll-a concentrations. I will compare the spatial and temporal difference between marine mammal sightings and these frontal boundaries. Oceanographic cruises aboard the Orion provide an excellent platform for regular marine mammal surveys to assess the current range of species present in Ecuadorian waters as well as establish a system of surveys that will improve marine resource management in this sensitive ecosystem. These surveys combined with remote sensing data from MODIS, will also provide useful insight into how the distribution of marine mammals is structured in relation to physical environmental features and the underlying biology. Ultimately, we hope to improve the tools and conservation methodologies available to marine resource managers.