Sighting Whiscash leaping from the water is believed to herald an earthquake. Whiscash is extremely territorial. Just one of these Pokémon will claim a large pond as its exclusive territory. If a foe approaches it, it thrashes about and triggers a massive earthquake. It makes its nest at the bottom of swamps. It will eat anything--if it is alive, Whiscash will eat it.
Pokédex entry #340
Whiscash in Pokémon GO
It's possible to hatch Whiscash from an egg?
No, Whiscash can't be hatched.
Which are Whiscash’s strengths and weaknesses?
Whiscash is a ground and water type Pokémon. ground type pokémons are strong against fire, electric, poison, rock, steel pokémons but weak against grass, bug pokémons. They are not affected by flying type pokémons. water type pokémons are strong against fire, ground, rock pokémons but weak against water, grass, dragon, electric pokémons.