Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You haven't learned this reading yet, so here's a mnemonic to help you:

While you live as a normal human citizen you also have another life as a cutter walrus (かたわ)! That's a walrus that cuts fish up while eating. It's your secret double life. You do it at night while you are a human by day!