HYDROPHONE STATIONS – LISTENING TO WHALES LIVE
We realized very quickly that if you want to study whales you need to listen in to their world. For this reason we installed a network of hydrophone stations from Douglas Channel to Caamano Sound ranging from 3 to 30 km from the research facility, Cetacea Lab. The installation and maintenance for each station took a lot of preparation and patience. Once ideal locations were established, the next step was to dive to a depth of 60-80 feet to secure the hydrophone, ensuring the best possible opportunity to hear whales from a distance. A cable connected to the hydrophone is connected to a land- based transmitter. The radio transmitter then broadcasts all whale vocalizations back to Cetacea Lab. All stations are powered with solar panels, wind generators and 12 volt batteries. We monitor these underwater sounds continuously in the lab, day and night, all year round. When calls are heard we digitally record the vocalizations directly onto our computer. From these recordings we are able to monitor the movement patterns of different orca and humpback whale populations. This method of research is ideal and allows for an acoustic window into the lives of cetaceans. We are no longer dependent on weather conditions or daylight. More importantly, we are able to collect all acoustic information without having an impact on the whales.
This year we begin the next phase with a new hydrophone project in collaboration with the Gitga'at First Nation and WWF-Canada. We recently installed a state-of-the-art long baseline hydrophone array in the coastal waters of Squally Channel, west of Gil Island. This array consists of four hydrophones, providing a wide bandwidth of 10 Hz up to 100 kHz. Each hydrophone is equipped with GPS clock providing microsecond time accuracy between each station. It acoustically monitors a terrain of about 200 km² in an area that needs to manage the balance between high cultural and commercial use, including proposed shipping routes for liquefied natural gas projects. This area has been identified as potential critical habitat for several at-risk marine mammals, including two distinct populations of orca as well as both humpback and fin whales.
The hydrophones in Squally Channel allow the 3D-localization and subsequent tracking of a vocalizing whale, as soon as a signal has been detected on all four hydrophones.
This hydrophone project is being developed by Ben Henricks through a Mitacs ELEVATE Postdoctoral Fellow in partnership with the Gitga’at of Hartley Bay, WWF-Canada, and NCCS. Ben finished his PhD in 2015 with a focus on observational astrophysics with a strong skill set in statistical analyses of large data samples, data processing and image manipulation, programming, project planning and project management.
Ben’s part in this project is to develop the software that allows automated detection, classification, localization, and tracking of transient signals of marine mammals from long baseline array data, such as the Squally Channel Hydrophone Array. The software aims to provide the following information to the user in real-time: detect if a whale vocalized, determine when the vocalization happened, classify which whale species vocalized, and compute where it happened.
The primary goal is to use the acoustic data to analyze the presence, activity, and movement patterns of the different whale species in the area. Furthermore, acoustic recordings from the hydrophone array will be analyzed to monitor the ambient noise level in Squally Channel, as well as the additive noise though industrial noise such as ship traffic. This hydrophone project and the Gitga'at Research Station will work hand in hand to provide both acoustic and visual data to study the impact of ambient noise on whales in the area. Thus, marine management will be improved, and research on habitat use of cetaceans and their interactions with marine vessels will be facilitated.