I am unable to think of any fish that copulate. However they surely do defecate. And the seagulls.......I used to live near a public water supply. The Water Department employees used to get nasty about people even parking beside the road on a causeway that crossed it. Once when they ordered me to leave, I pointed to the macadam surfaced road which was snow white with seagull poop, and asked why they didn't put diapers on the seagulls.