Presentation Title

P-25 Characterization of Side Scan-sonar Images Produced by Amazonian River Dolphins (Inia Geoffrensis) to Reduce Potential Confusion during Surveys of Amazonian Manatees (Trichechus Inunguis)

Presenter Status

Associate Professor, Department of Biology

Second Presenter Status

Student, Laboratório de Ecologia e Conservação da Megafauna Marinha -EcoMega

Third Presenter Status

Researcher and Lab Director, Amazonian Aquatic Mammal Lab

Preferred Session

Poster Session

Start Date

25-10-2019 2:00 PM

Presentation Abstract

Side-scan sonar (SSS) has been successfully used to detect West Indian and African manatees; however, sonar images of Amazonian manatees have yet to be obtained. One potential difficulty is differentiating manatee images from other large aquatic vertebrates. The Amazonian manatee shares its habitat with two cetaceans, the Amazonian River dolphin (ARD, Inia spp.) and the Tucuxi (Sotalia fluviatilis). In this study we characterize the sonar image produced by the ARD and note their behavior during surveys for Amazonian manatees. Boat surveys using SSS were conducted during the high (15-30 July 2017 and 17-21 March 2019) and low (13-21 December 2017) water seasons in Amanã Lake, Amazonas, Brazil. ARD acoustic images contain sharper angles and narrower shadows compared to manatees. At slow speeds (1-3 km/h), the shadow resembles an ARD, with a low profile dorsal fin, a narrow beak, and a narrow tail with a fluke. At faster speeds (4-5 km/h), the acoustic image can be elongated with a wavy tail due to the ARD swimming alongside the boat. ARD in Lake Amanã repeatedly followed our boat for kilometers during several hours, swam under the boat and approached the SSS transducer, suggesting they could hear the sonar, but were not distressed by it. ARD were usually seen in small pods (1-4); however, several pods would aggregate over time in relatively large numbers (10-20). In conclusion, ARD acoustic images have unique characteristics and can be reliably distinguished from known manatee acoustic images, though care must be taken when surveying for Amazonian manatees.

Acknowledgments

Partial funding provided by Andrews University Faculty Research Grant and Instituto de Desenvolvimento Sustentável Mamirauá.

This document is currently not available here.

Share

COinS
 
Oct 25th, 2:00 PM

P-25 Characterization of Side Scan-sonar Images Produced by Amazonian River Dolphins (Inia Geoffrensis) to Reduce Potential Confusion during Surveys of Amazonian Manatees (Trichechus Inunguis)

Side-scan sonar (SSS) has been successfully used to detect West Indian and African manatees; however, sonar images of Amazonian manatees have yet to be obtained. One potential difficulty is differentiating manatee images from other large aquatic vertebrates. The Amazonian manatee shares its habitat with two cetaceans, the Amazonian River dolphin (ARD, Inia spp.) and the Tucuxi (Sotalia fluviatilis). In this study we characterize the sonar image produced by the ARD and note their behavior during surveys for Amazonian manatees. Boat surveys using SSS were conducted during the high (15-30 July 2017 and 17-21 March 2019) and low (13-21 December 2017) water seasons in Amanã Lake, Amazonas, Brazil. ARD acoustic images contain sharper angles and narrower shadows compared to manatees. At slow speeds (1-3 km/h), the shadow resembles an ARD, with a low profile dorsal fin, a narrow beak, and a narrow tail with a fluke. At faster speeds (4-5 km/h), the acoustic image can be elongated with a wavy tail due to the ARD swimming alongside the boat. ARD in Lake Amanã repeatedly followed our boat for kilometers during several hours, swam under the boat and approached the SSS transducer, suggesting they could hear the sonar, but were not distressed by it. ARD were usually seen in small pods (1-4); however, several pods would aggregate over time in relatively large numbers (10-20). In conclusion, ARD acoustic images have unique characteristics and can be reliably distinguished from known manatee acoustic images, though care must be taken when surveying for Amazonian manatees.