Complementary methods to estimate population size of Antillean Manatees (Sirenia: Trichechidae) at Cienaga de Paredes, Santander, Colombia

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G.K. Arevalo-Gonzalez
D.N. Castelblanco-Martinez
P. Sanchez-Palomino
H.F. Lopez-Arevalo
M. Marmontel

Abstract

Information on manatee population size in Colombia is limited. This study was aimed at determining manatee population size in the Cienaga de Paredes (Colombia) by three different methods: boat-based surveys, side-scan Sonar (SSS) surveys and local interviews. Manatees were counted during breathing events by direct observation during the dry season, with the number of sightings per hour (NSH) and maximum number of simultaneous sightings (MNSS) used as occurrence indices. In 2002, we obtained an average NSH of 27.62 (SD=12.34) and the MNSS was 18; in 2010 the values were 55.71 (SD=29.79) and four respectively. Using linear-transect SSS data we estimated a population size of 12 individuals (%CV=27.3). The local community claimed that no hunting or entanglements had taken place in the area for over 20 years. These methods have pros and cons in terms of investment, effort, efficiency and community involvement, and their efficiency may vary in different seasons. Applying them in a complementary way and at greater spatial and temporal scales could enhance the accuracy of results.

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Short Communications