You know what they say: It's not the size of the fish penis, it's the motion in the ocean.
A study from the Australian National University dove into the breeding habits of fish to see whether big genitals made males more attractive partners for making babies.
The results bore good news for the less endowed: Females didn't show preference toward the, er, larger males.
For this study, the team observed the mosquitofish, which has what's called a gonopodium: a modified anal fin the male uses to hook into a vent on the female fish and shoot in sperm.
The gonopodium is roughly 30% of the fish's length.
"To our surprise, we found the size of the gonopodia made no difference to which fish successfully became fathers," Megan Head, from the ANU Research School of Biology, said in a press release.
Head was surprised, but that's understandable: If the way you have sex is with a sperm-firing harpoon that lodges in your vagina, you probably don't want that thing any bigger than it already is.