“If you are a female and are looking for the male that’s the most fit, one of the most obvious signs is size,” Muir said. “If you’re a big male, you must have survived, you must have been able to get food and have all the good genes. But in the case of transgenic salmon, I hypothesized this was false advertising. It was big, but not because it had the good genes or that it could find a lot of food. It’s big because of the transgene, and it actually has lower fitness than the wild type. So females would be mating with less fit males and it would perpetuate fewer offspring to maturity.”