Listening for Vaquita

The other day, I had the opportunity to join the corsair, a 21-foot tri-maran sailing out of San Felipe everyday to search for vaquita. Rather than posting visual observers to find the animals - specialists with binoculars scanning the horizon in search of the tiny dorsal fin or blow of the vaquita - researchers on the corsair are increasing their odds of finding the animals by listening for the vocalizations underwater. Because these animals are so difficult to detect at the surface, some of the world’s leading bioacousticians who specialize in porpoise echolocation and detection are here in town. Bioacousticians are scientists who study the sounds animals produce, or how sound can affect the animals. Here in Mexico, bioacousticians specializing in cetaceans (whale, dolphins and porpoises) are designing research strategies to be implemented by Mexican and US research ships in the northern Sea of Cortez to monitor the vaquita They are hoping to use different devices to monitor sound produced by the animals. The techniques vary for making recordings in the short term of this research expedition, and in the long term over the next ten years. [RAW]

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All toothed whales ‘echolocate’. Echolocating animals emit calls out to the environment, and listen to the echoes of those calls that return from various objects in the environment. They use these echoes to locate, range, and identify objects, during navigation and foraging. Some species also emit high frequency whistles when communicating with each other. Here in the northern gulf, scientists have designed techniques to utilize underwater recording devices called hydrophones to listen for the echolocation clicks made by vaquita, and to determine their location.

The Corsair is the smallest boat in the vaquita research fleet. In recent days, they have detected vaquita vocalizations using their hydrophone array – a 25-meter pair of hydrophones in an oil filled tube dragged behind the boat. It is connected to a computer running a software program called Rainbow Click. Rainbow Click visually displays acoustic detections on a screen and is constantly recording an audio signal from the hydrophones. Designed by Jonathan Gordon and Doug Gillespie of the Sea Mammal Research Unit at St. Andrew’s University in Scotland, it is a tool that I am very familiar with, and have used around the world to search for sperm whales.

By towing an acoustic array behind a boat, a trained user of the software can follow sperm whales for hours, or even days as long as at least one sperm whale in a group keeps ‘clicking’.

All porpoises, including the vaquita, produce rapid bursts of echolocation clicks. Unlike the clear, constant, slow pattern of clicks displayed on Rainbow Click when tracking sperm whales, the information displayed when vaquita are in the area leaves the screen awash with a mess of color, making it far more difficult to determine their location. This is the reason why so many experts are here. They aim to figure out the best method, or combination of methods to use.

The software program RAINBOW CLICK displays the background "snapping shrimp" recorded in the northern gulf of California When you are on the sea in the northern gulf, it is like being in an open-air cathedral – silence dominates the ‘topside’ environment. So much so, that when I am out on the panga rolling with the gentle swell, it acts like a giant rocking chair. In the scorching desert heat, there are times I just want to lay down and fall into a deep sleep; the kind you have when everything around you stops and the world falls quiet. However, drop a hydrophone into the water and it’s as if every sound of New York City is being pumped into the water live via the Internet, and combined into rhythmic white noise. Cacophonous clicks from snapping shrimp (or some type of crustacean) are everywhere. Biologists are not sure what exact species is producing such loud sound, but it definitely turns the underwater realm of this seemingly tranquil oasis into a dissonant symphonic crackling orchestra in all directions.

Listen to Audio Audio of background environmental noise recorded from the acoustic array on the Corsair. Courtesy of René Swift.

The ultimate challenge for the bioacousticians is to design techniques that will filter out nature’s background noise in order to find the world’s smallest cetacean on a regular basis, to monitor their progress over the coming years, and hopefully document population growth, rather than slide towards extinction.

Enter, Jonathan Gordon of St. Andrew’s Sea Mammal Research Unit, Jay Barlow of NOAA Fisheries - Southwest Fisheries Science Center, Tom Akamatsu of Japan and Nick Tragenza of the United Kingdom. If there were a “dream team” in the world of porpoise bioacoustics, these guys would be leading contenders.

Map of the corsair trackline and Vaquita acoustic detections. Courtesy Rene Swift.

I travelled down to the dock to meet up with the crew of the Corsair, captained by an old friend I have shared many adventures with at sea – Rodrigo Olson. I have sailed with Rodrigo on various parts of the Voyage of the Odyssey expeditions in Papua New Guinea, Western Australia, Sri Lanka, Maldives, and the Seychelles. He is originally from Ensenada, Mexico, and if there is one person you want captaining a sailboat, it’s Rodrigo.

Shannon Rankin of NOAA Fisheries - Southwest Fisheries Science Center is leading the bioacoustics field research program on the Corsair, along with researcher Renee Swift of Sea Mammal Research Unit in Scotland. Today, Jay Barlow and Jonathan Gordan decided to go out on the tri-maran to take a look at the array setup, and test a couple of new acoustic components to detect porpoises.

We left at 8:30am. About one kilometer out to sea, René and Jay deployed the acoustic array with a few additions strapped onto the cable. They attached a couple of Tom Akamatsu’s “pods”, live recorders collecting real time data that will add to the information gathered from Rainbow Click.

Rocas Consag. Photo - Chris Johnson

The wind was blowing at about 8-10 knots, a perfect day to sail the Corsair. We sailed around Rocas Consag, and came upon a mass feeding frenzy of dive-bombing boobies, frigates, long-beaked common dolphins and California seal lions.

We rounded Rocas Consag and headed back into San Felipe when the wind dropped, seas smoothed out, and sails flapped without purpose. Although, not good for propelling a sailboat under natural conditions, it became perfect weather for filming. Before we started the engine, I took out the video camera out of my dry-bag and asked Jonathan and Jay some questions about the acoustic challenges in listening for and detecting vaquita.