Massive Marine Carnage: Millions of Fish Perish in Mere Hours, Smashing Previous Records
Around the spooky season of Halloween, scientists have unveiled an uncanny spectacle of carnage in the ocean depths. These researchers followed a colossal swarm of cod off the Norwegian coast, witnessing as the fish mercilessly devoured millions of migrating capelin fish. This event appears to be the biggest predatory massacre of its kind ever documented by humans.
Various marine species gather for safety and migrate between regions, subsequently providing ample opportunities for cunning predators to exploit food sources. However, it is only recently that scientists have managed to consistently monitor large populations of fish, or shoals, enabling them to observe these floating smorgasbords in real time. Employing an acoustic sonar technique named Ocean Acoustic Waveguide Remote Sensing, or OAWRS, oceanographers in Norway and MIT tracked such a food bonanza.
The researchers targeted populations of capelin (Mallotus villosus), small fish similar to anchovies, encountering larger Atlantic cod (Gadus morhua) – their primary predator – in Norwegian coastal waters during their spawning season in February 2014. Initially, the disorganized capelin began aggregating into a massive shoal, numbering approximately 23 million fish spanning across miles. This vast concentration then triggered the cod to assemble and feast on the capelin. Over a four-hour period, the cod were estimated to have consumed roughly 10 million capelin, following their initial shoal formation.
"Investigations utilizing OAWRS for various regions and time periods could lead to a more profound and accurate comprehension of large marine ecosystems, in addition to aiding in the quantification of crucial processes in the assessment and management of marine resources over vast expanses," the researchers emphasized in their study, which was published today in the journal Nature Communications Biology.
Fortunately, this feast was not quite enough to significantly impact the capelin population. Experts estimate that billions of capelin migrate across the northeast Atlantic Ocean annually, meaning the cod likely consumed only about 0.1% of the local population that year. These large-scale events contribute to the ecosystem's equilibrium between predators and prey.
Regrettably, both capelin and cod populations have exhibited a decline in recent times, owing to factors like excessive commercial fishing. Climate change may further weaken capelin, potentially making such events more detrimental to their overall population health.
"Our research reveals that natural, catastrophic predation events can alter the local predator-prey balance within just a few hours," senior author Nicholas Makris, a mechanical and ocean engineering professor at MIT, shared with MIT News. "Such events would not pose a threat to a robust and diverse population with numerous population centers or ecological hotspots. However, as the number of these hotspots decreases due to climate and human-induced pressures, a 'catastrophic' predation event targeting a keystone species could have severe consequences for that species as well as the many species that depend on them."
At the very least, this technology will allow researchers and other concerned parties to more easily monitor the well-being of these vital marine species going forward.
The advancements in technology and science, such as the use of OAWRS, open up opportunities for more comprehensive studies of large marine ecosystems, potentially aiding in the management of marine resources. In the future, these advancements could help us better understand and mitigate the impact of catastrophic predation events, which can significantly alter the balance between predators and prey in marine environments.
