In 2001, Sweden’s National Board of Fisheries researchers observed brown trout in an aquarium and found that females faked orgasms. The females duped potential partners into premature ejaculation to avoid mating with undesirable males or attract more partners, biologists suggest.
As courting pairs of brown trout prepare to spawn, both fish quiver violently with their mouths open. Usually eggs and sperm are then released simultaneously, to maximise the chances of fertilization. Sometimes, though, the female quivers without releasing her eggs. Researchers Erik Petersson and Torbjörn Järvi found that females faked orgasms in 69 out of 117 couplings.
So which male does the female fish actually choose to release her eggs to for fertilization? Researchers found that the females often choose the male fish with bigger fins and jaws.