Answer :

I think the fish are dying because of the water slide. Five years ago the water slide was built and at that same year the fish started dying. The chlorine and chemicals from the waterslide to keep it clean, probably are killing the fish. Also maybe when the toy factory produces waste, it added on to the chlorine and killed the fish. Another thing that could have added onto the waste was the growth in the city ten years ago. The city probably produced more waste and the toy factory produced waste, and the chemicals combined together probably make it very dangerous for the fish so most of them die