Marine mammal distribution in Ecuador: surveys aboard a ship of opportunity as a means of monitoring relative abundance


  • Julia Elizabeth O'Hern The Marine Mammal Center P.O Box 778 Moss Landing, CA 95039
  • Michelle Sculley JIMAR- University of Hawaii NOAA PIFSC 1845 Wasp Blvd, Honolulu, HI 96818, HI
  • Kerri Jean-Smith Texas A&M University Department of Veterinary Pathobiology 400 Raymond Stotzer Parkway 77843 College Station, TX
  • Douglas Biggs Texas A&M University Department of Oceanography 797 Lamar St, College Station, TX 77843
  • Niall Slowey Texas A&M University Department of Oceanography, 797 Lamar St, College Station, TX 77843
  • Daniela Alarcon Ruales Universidad San Francisco de Quito Avenida Alsacio Northia frente a Playa Mann Isla San Cristobal, Galápagos, Ecuador
  • Roxanne Duncan Galway-Mayo Institute of Technology Marine and Freshwater Research Center Dublin Road, H91 T8NW Galway



distribution, ships of opportunity, visual survey


Five marine mammal surveys between 2008 and 2011 were conducted aboard the Buque de Investigación Orion (the research vessel for the Oceanographic Institute of the Ecuadorian Navy) within oceanic waters adjacent to mainland Ecuador and the Galápagos Islands. The surveys dedicated extensive time in deep, offshore waters where cetaceans were not densely present. Sightings of 12 species were compared with an earlier survey aboard the B/I Orion in 2001 as well as with a subset of published data from three NOAA STAR (Stenella Abundance Research) surveys between 1999 and 2003. Additionally, a small boat, near-shore survey, was conducted during June 2010 among and
near the Galápagos Islands. Encounter rates ranged annually from 0.012 cetacean/km to 0.027 cetacean/km. The highest encounter rate aboard the B/I Orion took place during the April 2009 survey. In order to compare sighting
rates between the B/I Orion and NOAA platforms, the average effective half-strip widths were used to determine encounter rates per area effectively searched. A zonation within the study region was observed between odontocete and
balaenopterid cetaceans as well as between striped (Stenella coeruleoalba) and short-beaked common dolphins (Delphinus delphis). Several methodological aspects of surveys and geographical features that may influence encounter rates and subsequent abundance estimates are discussed. This study demonstrates that vessels of opportunity provide a valuable means of studying open-ocean and coastal distributions of marine mammals. Possible methodological improvements, such as the use of high-power binoculars, that could increase the absolute number of sightings, the efficiency of these opportunistic surveys, and improve the sighting rates of more evasive species are discussed.

Author Biographies

Julia Elizabeth O'Hern, The Marine Mammal Center P.O Box 778 Moss Landing, CA 95039

Monterey Bay Operations Manager

Veterinary Sciences

The Marine Mammal Center

Douglas Biggs, Texas A&M University Department of Oceanography 797 Lamar St, College Station, TX 77843

Professor Oceanography

Niall Slowey, Texas A&M University Department of Oceanography, 797 Lamar St, College Station, TX 77843

Professor Oceanography

Roxanne Duncan, Galway-Mayo Institute of Technology Marine and Freshwater Research Center Dublin Road, H91 T8NW Galway

Doctoral student


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