Over the years, scientists and managers have developed tools for assessing fish habitat such as sonar and remotely operated vehicles. However, sometimes seeing the interactions between fish and their environment first hand is important for understanding how fish habitat is used. One way to achieve this is by training scuba divers to conduct research underwater.
The scuba system most commonly used today was originally developed in 1942 by Emile Gagnan and Jacques-Yves Cousteau, the famous French oceanographer, whose underwater research paved the way for decades to come. The device, called the Aqua-lung, allowed them to explore underwater without being tethered to a surface air supply; scuba was originally an acronym for “self-contained underwater breathing apparatus”, but is currently accepted as a common word.
Today, researchers use scuba to conduct a variety of underwater projects including fish surveys, evaluating habitat status, identifying new species, and assessing the impact of invasive species, among many others. But to be a safe and effective underwater researcher, you need more training than the basic scuba course required for recreational divers. Scientific divers make observations, record data, and use tools to construct experiments all while practicing safe diving principles. Throughout the dive, a researcher must also maintain communication with another individual, their dive buddy, monitor their own air consumption and make sure they don’t exceed their limits. Communication is limited to about a dozen simple hand signals, the use of an erasable slate or, in special cases, divers may be trained to use full face masks fitted with a transceiver for voice communication. This communication challenge makes detailed planning prior to the dive necessary. Tasks that seem simple at the surface often become challenging when divers encounter environmental conditions such as cold water, strong currents, or low visibility, making extensive training and experience essential to completing the research safely.
Due to the working nature of science dives and stressors that divers may face, most scientific divers participate in specialized training courses where they learn advanced rescue skills, dive planning, and research protocols, among others skills. When the target research area is deep enough, researchers must also be trained as “technical” divers, who dive deeper and longer than the recreational limits.
Whether diving to 20 feet in a warm lagoon, or 200 feet in a fjord, divers have a limited amount of time that they can spend underwater and have to develop clear and simple protocols for conducting research. The exact data and parameters collected vary depending on the specific project or location, but there are a few basic protocols commonly used for assessing habitat. Two examples of these protocols include the towed-diver survey and the quadrat survey:
Towed-diver survey – A towboard platform with survey equipment (such as an underwater camera) is towed behind a small boat at a constant speed while a diver hangs on and maneuvers the towboard. This type of survey reduces physical exertion of the divers but requires careful coordination with the boat crew.
Quadrat surveys – a frame made out of PVC or other lightweight material, typically a 0.5×0.5 meter or 1×1 meter square, is placed at intervals along a transect tape and data are recorded for the area within the frame (see embedded video for example). This survey style is easily adaptable to different habitat types and project needs.
Other protocols may include the use of underwater scooters, stationary experimental plots, species collection, sediment core collection, or even tagging of target species.
Interested in becoming a certified diver?
A few common recreational dive agencies include the Professional Association of Diving Instructors (PADI), the National Association of Underwater Instructors (NAUI), and Scuba Divers International (SDI). Technical Diving International (TDI) is the largest certification agency in the world for technical diving. Organizations that conduct scientific diving throughout the US are often members of the American Academy of Underwater Sciences (AAUS), whose mission is to facilitate safe and productive diving for a scientific purpose. Individual divers may participate in a Scientific Diver certification through an AAUS organizational member in order to learn specialized skills for conducting research and data collection while utilizing scuba as a tool.
While there are numerous techniques that allow scientists to learn more about how fish use their habitat, scuba diving is a unique way to for researchers to be immersed in very environment that they’re studying. While this approach requires special training and skills, the knowledge rewards and thrills of exploration make it all worth the extra effort.
Below is a short video demonstrating how a habitat survey in eelgrass might be conducted using quadrats:
Special thank you to Christopher Rigaud and Tyler Phelps for providing pictures and video content for this post.
For more details about different survey methods, visit NOAA’s website at: https://www.pifsc.noaa.gov/cred/