Before the Nile perch were introduced cichlids thrived. There were around 500 different types of them.
The perch started off slow but eventually started eating a lot of cichlids in a matter of time perch made up over half of the fish in Lake victoria.
Because fishing was a good job to get people started getting bigger boats so that they could carry the big fish.
Things only got worse. Algae started to rapidly grow. Since there wasn't that many cichlids they couldn't eat it all. The water got dirty and the fish couldn't see each other and couldn't mate.
All the algae made most of the oxygen disappear an that killed a lot of the remaining cichlids.
Another problem came to Lake Victoria. A new plant from South America called the water hyacinth spread fast along the coast where fish would lay there eggs. It also stopped boats and clogged pipes. Another bad reason is that it spread diseases like malaria.
The government started to sell the fish that the fisherman caught to different markets to make money.
After the government did that people in that area lost about 40% of there protein.