New Delhi: A research by oceanographers from MIT and Norway has described the biggest predation in the ocean as cod feeding on capelin in the boreal region of Norway. The researchers used an impressive method of acoustic surveying that allowed them to witness cod feeding on more than ten million capelin in several hours, which demonstrated complex interactions of predators and prey during the spawning season of the latter.
The team used the Ocean Acoustic Waveguide Remote Sensing (OAWRS) system on a 2014 expedition to the Barents Sea. This technique uses a kind of vertical sound wave projector that transmits sound waves into the ocean to gather information on marine life in large regions. In this case, applying a new multispectral analysis on the same data allowed the researchers to distinguish between the fish species using the physical properties of the swim bladder’s sound frequencies to track the movements of capelin and cod at the same time.
Novel Aspects of Shoaling Phenomena
Increased sampling during the late February when capelin is spawning, identified a single large shoal of capelin estimated to be 23 million strong. While doing this and moving in a coordinated way, these fish were able to aggregate a number of other migrating cod fish which also formed their shoal. The cod was able to dominate the capelin and within several hours consumed more than half of the collected prey. This interaction is a major step forward in the study of large scale predation events in marine communities.
Ecosystem Health Consequences
While the event itself makes up only 0.1 percent of the capelin stock in the region, concerns over the future of this keystone species are raised by the changes in the spawning season due to climate change. With receding ice in the Arctic regions, the capelin may be pushed to longer distances, which will expose them much to the predators. Nicholas Makris of MIT said that understanding these predation dynamics are important in the health of the ocean’s ecosystems especially given the fragility of fish populations due to climate change and other human factors.
The work also shows how the OAWRS system can be useful in helping to improve marine research and monitoring activities. As the technology progresses researchers strive to study the behaviours of different types of fish more in order to gain valuable information on fish populations before these populations are greatly diminished. It has the potential to revolutionise current methods used in marine biology by providing unprecedented perspectives of what may be going on within underwater environments.
