Active sonar survey of manatees in western Panama: Complete data.

ABSTRACT The Antillean manatee (Trichechus manatus manatus) is found in tropical and subtropical riverine and coastal waters across the Caribbean region. Little is known of its population status, particularly in Central America. We counted and mapped manatees using side-scan sonar in the San San Pond Sak wetland, a protected estuary in western Panama, for 12 months, and converted the sightings into density and abundance estimates. Overall, 214 sonar transects were conducted, covering 1731 km and detecting 1004 manatees. The highest density of animals was found in the narrow and relatively deep upstream tributaries and also in a shallow lagoon near the river mouth. The estimated mean number of manatees in the 18-km San San river system over the year was 18.3, but abundance was highly seasonal, with 33 animals present in May and just 2 in December. These figures are within the range reported for similar rivers in Central America and Florida. Uncertainty of the population size was estimated with a Bayesian model, using daily variance in counts, and 95% credible limits were 22-71 animals at peak season but just 1-6 in December. The active sonar survey used in this study located manatees, mapped their positions, and converted sightings into quantitative data for rigorous analysis. The method is cost-effective for repeated counts across seasons and years, needed to evaluate population trends.

Results of an analysis of the data is published in:

Guzman, H.M. and R. Condit. 2017. Abundance of Manatees (Trichechus manatus) in a Panamanian Wetland Estimated from Side-Scan Sonar. Wildlife Society Bulletin.

Two data files are provided. 

File 1: ManateeTransectArchive.tab. Tab-delimited ascii. Details of each of 214 transects on San San River in Bocas del Toro using active sonar to count manatees. The column 'tranID' is an identifier for each.

tranID: Arbitrary integer identifier of transect
date: Date
duration_min: Time elapsed from start of transect to end
area_ha: Estimated area in hectares, using river width calculated from satellite map
UTM_startX: Starting coordinates of transects, UTM easting, zone 17
UTM_startY: Starting coordinates of transects, UTM northing, zone 17
UTM_endX: Ending coordinates of transects, UTM easting, zone 17
UTM_endY): Ending coordinates of transects, UTM northing, zone 17

File 2: ManateeSightingArhive.tab. Tab-delimited ascii. Details of every manatee recorded by sonar on those transects. Groups of manatees close together were entered in one record, and the column 'manatee_count' gives the group size.

manID: Arbitrary integer identifier of the record
tranID: Links to tranID in ManateeTransectArchive.tab
manatee_count: Count of manatees in the group
time: Local time when manatees were detected
lateral_dist_m: Distance from boat to manatee group, recorded by the sonar
UTM_X: Coordinates of boat when manatees were detected, UTM easting, zone 17
UTM_Y: Coordinates of boat when manatees were detected, UTM northing, zone 17