A Jack Trout is a smaller trout that swims quickly through a bed of eggs releasing his sperm as he goes through, fertelizing eggs as he goes. He is too small to defend any territory and therefore has to resort to this type of behavior to reproduce. Early maturing, dwarf "jack" or sneaker males return to their home stream every year; "hooknose" males do so after several years in the ocean. The latter are not only larger, but also more colorful. Aggregations surrounding a female are composed of both "jacks" and "hooknose" males. Once the female releases her eggs, all males release their sperm, with the greater number of eggs being fertilized by the first male that enters the nest. Individuals of this species can reach 15 years of age in captivity.
Why didn't I think of this in college?