You might have heard of whales being ‘tagged’ with small sensors that use underwater acoustics to track whale migrations. Tags have been used for decades, but this technology has evolved quickly in recent years. In 2020, researcher Kim Holland and his team at the Hawaiʻi Institute of Marine Biology have begun using sophisticated tags on tiger sharks to compile data to feed into their oceanographic and meteorological models. The tags are microcomputers equipped with sensors and LEDs that measure ocean depth, temperature, salinity, dissolved oxygen and light levels. To actually attract the tiger sharks for tagging, the researchers use bait and hooks on boats to catch and pull the shark close enough to secure it before flipping it over, putting the tiger shark in a temporary state of tonic immobility. For the few minutes that the shark is immobile, they measure it and attach the tag to the dorsal fin before it swims away. Data is transmitted back to the researchers via satellite the second the tiger shark breaches the surface because GPS and satellites cannot penetrate water. While no new innovations were made for satellite signals to reach the devices, no other devices are capable of cloud-computing in the extremely short time frame a tiger shark breaches the surface, making these fairly advanced telemetry devices. The available science that can be derived from just one study is maximized here, as scientists will be able to ask new questions about the ocean that were not possible before using these datasets that contain new information about ocean light levels, dissolved oxygen and depth.  It may be several years before any comprehensive data appears with this new generation of tags, but by then we will also know far more about the ocean, its ecosystems, and how it is changing due to climate change. Currently we know a lot about shallow areas of the ocean due to ease of access and through aerial imagery, but we know less than 95% about what happens in the ocean at depth, meaning there is no baseline climate model for deep-ocean spaces or understanding of the natural processes that take place there. The next generation of tags will help fill in this gap with their capacity to monitor new indicators for the marine environment and will help us start to map out Earth’s oceans. 

Block, B.A., Holbrook, C.M., Simmons, S.E., Holland, K.N., Ault, J.S., Costa, D.P., Mate, B.R., Seitz, A.C., Arendt, M.D., Payne, J.C. and Mahmoudi, B., 2016. “Toward a national animal telemetry network for aquatic observations in the United States“.