First field-based estimate of Antillean manatee abundance in the San Pedro River system suggests large errors in current estimates for Mexico
Periodo de realización: 1900/01/01 al 2017/01/01
Tipo: Artículo científico
Lugar(es) de estudio: Tabasco, Mexico, Chetumal, Quintana Roo, Mexico
Resumen: "The fluvial-lagoon systems like San Pedro River, a tributary of the Usumacinta, are important sites for the presence of the Antillean manatees. These systems are characterized by having complex water flows with high turbidity that historically difficult the manatees’ studies in the Mexican gulf hydrological basins. The aims of this work were to estimate the density of the manatees in the San Pedro River system and associated streams and to know how this density could vary due to changes in the water level. Our method to estimate density was based on Side Scan Sonar. Two navigation sessions by month from January to June of 2016 were realized, each one with three consecutive surveys. The navigation speed was 10 kilometers per hour (km/h) over 23 kilometers long transect, and detecting manatees with a Humminbird Side Scan Sonar (SSS). A total of 471 SSS records were obtained, 46 of them (10%) were calves and 425 (90%) adults. We determined the identity of four calves. Average density was 21.7 manatees per square kilometer (km2) fluctuating from 3.7 to 43.3 manatees per km2. Changes in their density are due to the variations of the water depth which allows or restrict the access to the manatees to the different water bodies that make up the system. During this study, it was estimated the presence of 28 manatees in the study area. Manatees’ density values were surprisingly low"