Tombstones of the fish in the school
Fish have swum at least 50 million years. Scientists have found 259 fossil fish embedded in old rocks, folded together and all pointing in the same direction – the oldest known evidence of school behavior.
Researchers from Arizona State University discovered fossil fish when they visited the collection at the Ossi Fossil Gallery at the Memorial Museum in Mizhta, Japan.
Scientists identify small fish such as Erismatopterus levatus, an extinct species that lives on Alpine lakes. Although the researchers were unable to prove the cause of death, the team of scientists suspected that the sand dune suddenly collapsed and swallowed and killed the entire fish school.
Because all fish point in the same direction, researchers assume that fossils are fish shoals. To explore their hunches, scientists have measured and determined the position of fish in detail. Using measurements, the researchers created a model to simulate fish behavior.
The model contains dozens of scenarios with different water flows and spatial distributions. Simulation shows that old fish streams have been formed for the same reason as fish today – to protect themselves from enemies. The model shows that the largest density of fish in the middle of the school is the safest.
Simulation results – detailed this week in the Proceedings of the Royal Society B: Biological Sciences – also show that fish schools are subject to the same two rules that determine modern school behavior: “Rejection from relatives and attraction neighbors.”
Hostility towards nearby fish helps prevent collisions, while neighbors who move a little further help fishery schools maintain their shape.
“Our study shows the possibility of exploring the social communication of extinct animals that cannot possibly leave the fossil record,” the researchers wrote.