People, animals and fish are souls. A body and the breath of life.
Rev. 16:3 And the second angel poured out his vial upon the sea; and it became as the blood of a dead man: and every living soul died in the sea.
Think of the body as a light bulb and the breath of life (spirit) as electricity. When you have them both together, you have light. If you take away the electricity, you have a dead bulb. Where did the light go? It didn't go anywhere. It just ceases to exist.
God can put them back together any time He wants.
Isaiah 49:16 Behold, I have graven thee upon the palms of my hands; thy walls are continually before me.
John 14:2 In my Father's house are many mansions: if it were not so, I would have told you. I go to prepare a place for you.
14:3 And if I go and prepare a place for you, I will come again, and receive you unto myself; that where I am, there ye may be also.
1Thessalonians 4:16 For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first: