Post copulatory opportunities for sperm competition and cryptic female choice provide no off spring fitness benefits in externally fertilizing salmon

Abstract

There is increasing evidence that females can somehow improve their offspring fitness by mating with multiple males, but we understand little about the exact stage(s) at which such benefits are gained. Here, we measure whether offspring fitness is influenced by mechanisms operating solely between sperm and egg. Using externally fertilizing and polyandrous Atlantic salmon (Salmo salar), we employed split-clutch and split-ejaculatein vitrofertilization experiments to generate offspring using designs that either denied or applied opportunities for sperm competition and cryptic female choice.