Goldfish are an invasive fish species, but don’t let that distract from the well-known fact that they make for wonderful household pets, especially if you enjoy the sight of a colorful aquarium.
If you spend enough time gazing at goldfish, you’ll start to learn something about their behavior – notably, the way they react to one another’s movements in the water. Even when one isn’t looking directly at another, it seems that a goldfish can detect that other goldfish’s presence and follow its lead, demonstrating strong coordination.
So how are they able to do this? It’s all thanks to a special line of sensory organs along the goldfish’s side known as the lateral line. It detects currents and ripples traveling through the water they swim in, alerting them to nearby movements and activity. In fact, scientists believe that this is how they follow one another with such precision in large schools.
The lateral line is both a communication tool for the fish and a means of the fish to detect potential predators. If the current is strong enough – obviously too strong to be created by a fellow goldfish – then the goldfish will know to swim in the other direction very quickly to avoid falling victim to predators.
Intriguingly, goldfish can also use their lateral lines as a means of flirting with others. They can create playful ripples in the water and rub up against others to generate playful sensations, as shown in the video above.