Fisheries & Aquaculture News

Vocal Group(er) Spawns Sound Data: Using Passive Acoustic Monitoring to Assess Marine Ecosystem Health

With anthropogenic noises in the ocean increasing, one researcher is studying how sound can be used as an index to measure the health and diversity of marine ecosystems.

At the 2016 International Ecoacoustics Congress held at Michigan State University (June 6-8), graduate student Katherine Cameron of Scripps Institution of Oceanography gave a talk titled, “Soundscapes of Multispecies Fish Spawning Habitat.”

Her research targets at least five types of grouper in the Serranid species, including the tiger grouper (Mycteroperca tigris), red hind (Epinephelus gutattis), the near-threatened black grouper (Mycteroperca bonaci), and the endangered and overexploited Nassau grouper (Epinephelus striatus). They share an active spawning area in the diverse reef community off of the Little Cayman Island, so this is where Cameron deployed continuous passive acoustic monitoring to “reveal temporal trends in both biological and anthropogenic activity.”

Recordings of the Nassau grouper and red hind grouper can be heard via the Scripps Institution of Oceanography Marine Bioacoustics Lab here.

Conservation efforts to protect the Nassau grouper spawning aggregate near Little Cayman have received special attention in the past, notably with the 2012 re-mastering of Guy Harvey’s documentary The Mystery of the Grouper Moon. Because this is still the largest known aggregation of the Nassau grouper, Cameron focused her research near Little Cayman.

During the spawning of the Nassau grouper, Cameron collected acoustic data for five days in February 2015 and thirty-three days in 2016, with extra recording during the month prior to spawning in 2016. Her monitors recorded sounds between 2 and 20 kilohertz, and she manually analyzed them to identify dominant sound sources and their related frequency bands. Once she isolated bands of fish sounds, she evaluated when they could be divided into narrower bands, from 100 – 200 hertz to learn about the type and timing of their vocalizations during spawning. In addition to bands of frequency, she also identified bands of pulse in order to get a baseline for the sound and management of the species. The data enables her to describe the Nassau grouper’s daily and lunar patterns as well as spawning site changes.

“Anthropogenic activity dominated during the day,” Cameron explained, “while fish chorusing peaked after sunset and showed lunar dependence.”

As she continues to analyze the results of her soundscape analysis from both the 2015 and 2016 deployments, she compares the calls that she logs to see if this research approach can support call rate estimation. Cameron described her work as “the first step towards characterizing the soundscape of this critical spawning habitat and an attempt to validate whether this is an appropriate method for long-term monitoring of the ecosystem.”

Funding from a National Defense Science and Engineering Fellowship supports this project.

The 2016 Ecoacoustics Congress included presentations about the passive acoustic monitoring of tropical, marine, terrestrial, and urban soundscapes. More information about the International Society for Ecoacoustics can be found here.

By: Beth Staley, ECO Contributor via West Virginia University

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