Yes, fish do have periods, though they’re not exactly like the ones humans experience. For starters, fish periods last for just a few days and occur once a month. Secondly, fish don’t bleed from their vaginae during their periods. Instead, they excrete a mucus-like substance.
So, why do fish have periods? Well, just like humans, fish need to release eggs in order to reproduce. The period signals to the fish that it’s time to release eggs. The eggs are then fertilized by the male fish and the cycle begins anew.
Interestingly, not all fish experience periods. Some fish, such as sharks, release their eggs into the water and the eggs are then fertilized externally. So, if you’re ever wondering whether or not your pet fish is on its period, now you know!