your mention of mosquito fish reminds me of holidays past, while the kids were growing up we used to take our vacations in the same place in Spain each year, Estartit, this place had a large marsh into which i would disappear for hours at a time the place teemed with these fish and i would sit quietly watching the young viperine snakes [natrix maura] hunting them i even brought some home and kept them for a number of years before stopping them breeding and letting them die out.
it never occurred to me that i might be breaking any laws [not sure that i did even now] we used to travel overland [not fly] so transport wasn't a problem and i never hid them at the custom point, one thing that puzzles me is that i was told back then that these fish were spread around the then known world by the ancient Romans to combat mosquito's but if they are a new world fish then this can not be true any ideas?