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SC/69A/CMP/14
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Resource ID
19967
Access
Open
Document Number
SC/69A/CMP/14
Full Title
Evaluating franciscanas individual cue rate: a step for density and abundance estimation through PAM
Author
Mura, Joao Pedro, De Oliveira, Lucas Lima, Silva, Barbara Stefanea, Amorim, Thiago O. S., Alvares, Diego, Danilewicz, Daniel, Andriolo, Artur
Authors Summary
Using the acoustic towed array method, the paper documented the franciscanas individual cue rate estimation to be applied as a correction factor for density and abundance estimation. This is the first synchronous approach to acoustic towed array PAM and Drone monitoring for cetaceans in Brazilian waters. The development of the sampling protocol and automated analysis was successful and can be reapplied in the same location as other FMAs. The cue rate obtained can be applied as a correction factor for abundance and density estimation of franciscanas using acoustic towed array PAM when that data is collected following the same protocols and equipment of this study.
Publication Year
2023
Abstract
The franciscanas (Pontoporia blainvillei) are the most endangered dolphins in South America. Its distribution is restricted from the Southeast of Brazil to the north of Argentina, and it is subdivided into franciscana management areas. Aerial survey is the method that currently presents the best results for estimating its abundance. More recently, the Passive Acoustic Monitoring (PAM) arose as an alternate method to investigate these population parameters, in specially, the towed array systems. The sampling unit in acoustics surveys could be echolocation clicks or echolocations click trains, which need to be converted to a rate that represents an individual, called the cue rate. This study applied synchronous drone and PAM sampling to estimate the franciscana’s cue rate. The field work was established in Ubatuba, São Paulo, Brazil. The main goal is to contribute to the development of a correction factor to acoustically estimate franciscanas density and abundance through PAM using towed arrays. A motorboat was used as a platform with an average speed of 4.18 knots, as well as a 50-meters AUSET recording system (SailDaq @500 kHz, four hydrophones, 50 kHz high-pass filter). The PAMGuard was used for recording, click detection, click classification and train identification. The drone DJI Phantom 4 was used for image collection maintaining constant flight above the hydrophone and a linear trajectory. To determine the standardization of the coverage area the GSD was applied. Thirty meters for each side of the transect line was considered as synchronous effort width. Eight campaigns were performed in the seven days of data collection. A total of 1,012 click trains (10,433 echolocation clicks) were identified. Three of the 14 sections presented visual and acoustic detection matches. In this way, the total average train/individual ratio calculated was 3.48 (variance = 4.2), with an average perpendicular distance of 18.31±4.35 meters. This result is an important step as it establishes a correction factor for franciscana density and abundance estimation through PAM using towed arrays.