"Where are Corphish, Carvanha and Lotad?"

#PokemonGO: Hey guys,So I still dont have a Corphish or a Carvanha, and I only found one Lotad since the last Gen 3 Pokemon were released. I'm playing in lures and catching around 300 Pokemon a day but they remain extremely rare.Is there a way to find them more easily? In which biome are they appearing? Can they nest or are they considered as non-nestable rares Pokemon such as Feebas, Slakoth and Ralts?Thanks in advance via /r/TheSilphRoad http://ift.tt/2DsFdgO