A recent fossil, discovered from the Eocene Epoch, shows that schooling is a trait among fish for nearly 50 million years.
For those of you who haven’t heard about the Eocene Epoch, it is the time period from nearly 56 to 35 million years ago. It is said that around this time, oceans were swarming with fish and other sea animals. Thanks to ecologist Nobuaki Mizomoto from Arizona State University, we know that fish moved around in large groups since then.
Mizumoto came across the slab of limestone with the fish fossils in Katsuyama, Japan in 2016. The slab fossilized 257 fish, all part of the same shoal. Mizumoto’s study showed similar patterns of co-existence in the shoal and current fish schools. This also establishes that fish behaviour has not changed drastically for over 50 million years.
The slab also showed how the fish were swimming in the same direction. The reasons for their death and subsequent fossilization are unknown. Mizomoto’s report shows how the fish remained a group but avoid collisions by tracking other fish in the shoal, much like fish do today. It is likely that fish did so then to protect themselves from large predators and other fish in the oceans. Not much has changed today, except that fish need to protect themselves from ocean dumps and plastic apart from predators and fishing trawlers.