It’s not just about the sperm: the semen of male fish carries unidentified substances that influence how quickly the offspring develop and even how well they can swim
Source:
https://www.newscientist.com/article/2232134-seminal-fluid-not-just-sperm-can-influence-offsprings-survival/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home