Traveling to freshwater lakes

That's what some researchers wanted to find out - how do fish get to isolated freshwater lakes. Their theory is that birds bring them there. And they do it via their digestive tract. The experiment involved whole killifish eggs. The eggs were put inside the digestive system of swans in Brazil. They found that an estimated one per cent of ingested killifish eggs were found to be viable in bird feces and capable of continuing their development. One egg in the study even hatched more than a month after its transit through a swan.