Passive acoustic monitoring (PAM) is an important ocean science tool for monitoring and understanding marine mammals and their behaviour. There is a variety of ways to do this, from handheld hydrophones to moored or towed PAM systems, each with different applications.

With the advancement in marine technology in the last two decades and particularly in autonomous vehicle development, new solutions for marine mammal monitoring are making data collection far easier and less resource intensive. One such solution is Autonomous Underwater Vehicles (AUVs) and their smaller siblings micro-AUVs.

Micro-AUVs provide a PAM solution which can cover large survey areas while remaining unintrusive. They also benefit from being able to switch their engines off at monitoring locations. In comparison, towed arrays continually emit vehicle noise which can mask the calls of and/or disturb any marine mammals in the area. Where strategic deployment is required to improve spatiotemporal coverage, a micro-AUV can be easily redeployed in the same location.

YUCO-PAM is an innovative autonomous solution for passive acoustic monitoring, equipped with RS Aqua’s Porpoise acoustic recorder. With a selectable sampling rate of up to 384kHz and a storage capacity of up to 8TB, the Porpoise can be programmed separately or activated by the AUV, synchronising its recordings with YUCO-PAM. This micro-AUV is designed for operation in coastal environments, reducing the need for larger vessels in the shallow, potentially challenging waters that are often a sticking point for autonomous systems.

YUCO-PAM deployed from a small boat.

Due to Seaber’s unique navigational technology INX©, YUCO-PAM can navigate incredibly accurately e.g. with less than a 1% error over a 1000 km range. Missions can be quickly and easily planned using Seaber’s proprietary SEAPLAN software, which supports a number of navigation patterns adapted to noise monitoring.

During a recent trial, YUCO-PAM was used to showcase these capabilities. It carried out continuous noise recording while navigating more than 25 nautical miles in a single mission. It also stopped to take recordings at predetermined locations, with its embedded pressure sensor and DVL enabling it to maintain a fixed depth or altitude. Importantly, the micro-AUV can kill its engines and slowly resurface offering completely uninterrupted recording and follow that with a precise GPS position of each recording.

Spectrogram showing dolphin whistles heard during navigation in a recent YUCO-PAM deployment test.

The above spectrogram demonstrates how clearly identifiable marine mammal noise is using the YUCO-PAM. The whistles seen on the spectrogram can also be heard in this audio excerpt from the trial.

Overall, the YUCO’s navigational capabilities coupled with the PAM features of the Porpoise offer a smart, non-intrusive and highly-customisable solution for noise monitoring. Available as ‘off-the-shelf’, the YUCO-PAM can be used for a wide range of applications from marine mammal and fisheries monitoring through to measuring anthropogenic noise pollution such as pile driving and shipping.

Images: Seaber

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