Fish spawn when a bucket of water is poured onto a sheet of ice

Fish continuously spawn when a bucket of water is poured onto a sheet of ice

What I expected to happen was...:
I expected the water to just flow or freeze

What actually happened was...:
Water flowed and fish would spawn within the flowing water

Steps to Reproduce:
1. Find a sheet of ice in a cold biome
2. Pour a bucket of water onto an open sheet of ice (only ocean ice?)
3. Fish will begin to spawn and get pushed to the edges of the puddle, then flop around on the ice until they die