Distribution of the Antillean manatee (Trichecus manatus manatus) in the Alvarado Lagoon System (Veracruz, Mexico)

Abstract

The Antillean manatee (Trichechus manatus manatus) is considered endangered in Mexico. Local extinctions have been documented in the northern Gulf of Mexico, and the only remaining population with a northern distribution is found in the Alvarado Lagoon System (ALS). The objective of this study was to determine manatee distribution in ALS. The system covers an area of 267,010 ha and includes hundreds of lagoons, floodable areas, and dozens of rivers. To detect manatees, systematic line transects were done in a boat 7.6 m in length, totaling 332.6 h of search effort with an average of 7.38 h d^–1 in 45 surveys. There was a total of 13 manatee sightings: seven direct sightings, five with hydrophones, and one with a side-scan sonar. For each record the geographical coordinates were taken and integrated in a geographical information system to analyze their distribution. Manatee distribution was not uniform throughout the study area. Manatees were sighted in very specific areas of ALS considered part of their habitat, mainly in areas with inland water bodies, in some estuarine and marshy areas, and in some wetlands with vegetation generally in appropriate condition. This lagoon system is very important for manatee conservation since it is the last site with viable populations in Veracruz and the northern Gulf of Mexico.