Using sound to track marine mammals in Saba Bank

Saba Bank is home to a diverse population of marine mammals. For many of these species, this area serves as a primary habitat for critical activities that include feeding, mating and calving. This is particularly true for a variety of dolphin and whale species. Historically, these species have been hard to track, as researchers are often dependent on visual sightings from fishermen or tourists to detect their presence. However, technological developments are now allowing researchers to listen and record underwater sounds, giving an unprecedented look into the lives of these animals.

Yarari Sanctuary

Since 2015, Saba Bank has been a part of the Yarari Marine Mammal and Shark Sanctuary. The sanctuary includes all the waters of Bonaire and Saba, and since September 2018, Sint Eustatius. This sanctuary was established to help protect the marine mammals and sharks around the Dutch Caribbean. The first step in protecting these waters is to support and promote projects which work to identify the species which can be found here. 

Many marine mammals rely on acoustics for spatial orientation, communication, mate attraction and foraging. Each species has the ability to create unique vocalizations and can often adapt these sounds based on conditions of background noise or distance to their targeted audience. Man-made noise can have a variety of negative impacts on marine mammals which can cause confusion, stress or changes in behaviour.

Saba Bank Noise Logger Project

Starting in 2011, the Saba Bank noise logger project has provided valuable information in support of conservation efforts by identifying the specific whale species which can be found in Saba Bank. These hydrophones (underwater microphones) can record continuously for six months at a time, and give researchers the ability to listen to a variety of marine species, from whales (and dolphins) to schools of fish. Noise loggers detect all ambient noise, including natural background noise produced by tidal current and waves, noise from marine animals such as fish or crustaceans (snapping shrimp) and anthropogenic noise from shipping, seismic operations and naval sonar. Then using the different sounds and frequencies, researchers are able to distinguish species, and their relative occurrence over time.

This project, commissioned by the Dutch Ministry of Agriculture, Nature and Food Quality, is a collaborative effort between Wageningen Marine Research and the Saba Conservation Foundation and is supported by international partners such as the Scottish Association for Marine Science (SAMS), the National Oceanic and Atmospheric Administration (NOAA) and CARI’MAM. The goal is to identify the temporal occurrence of cetaceans and where possible their acoustic behaviour (e.g. 'singing') and identify any other sounds of marine animals which can be detected within Saba Bank. This information will help conservationists and policy makers to draft effective management plans for endangered species in this region.

Results

The project was successful at detecting marine mammals such as dolphins, humpback whales and minke whales. It helped to better understand the migratory patterns of minke whales by comparing recordings in the Caribbean with other areas in the Northwest Atlantic. However, this information is only a small piece of the puzzle. The songs produced by humpback whale males can be further investigated to identify individual and local differences. Migratory patterns of humpback whales, both from their feeding grounds to the Caribbean as well as within the Wider Caribbean can be further investigated by linking data collected from other hydrophone stations. In the future detection rates of cetaceans could also be used in combination with visual surveys to improve our understanding of local densities and in the long run possibly population sizes.

Overall, this project has provided important insight into cetaceans using Saba Bank. Along with providing critical research and data to help support conservation efforts, this information could also help to develop a new economic source for the island. If the presence of whales and dolphins is better understood and can be predicted, sustainable marine mammal watching tours could be a new and popular tourist attraction for Saba. It is important that all stakeholders on the island work together to ensure these important species are protected and respected, while also working to enhance the lives of the local population. 

More information

• Presentation Underwater Sound around Saba Bank (pdf; 1.8 MB)
• Special Edition Yarari Marine Mammal and Shark Sanctuary (pdf; 15.1 MB)

Text: Dutch Caribbean Nature Alliance; Bart Noort, Wageningen Marine Research; Ayumi Kuramae Izioka, Saba Bank Managagement Unit
Photos: Ayumi Kuramae Izioka; Mark Vermeij