Short answers, pulled from the story.
Fishlike animals with a notochord and eyes at the front of the body appeared about 530 million years ago during the Cambrian explosion. Haikouichthys represents one of these earliest forms that lacked true jaws but possessed a distinct head structure.
As of 2016, there are over 32,000 described species of bony fish alone. Teleosts make up 96% of all living fish species today while cartilaginous fish account for over 1,100 species.
Coral reefs in the Indo-Pacific constitute the center of diversity for marine fishes globally. Continental freshwater fishes are most diverse in large river basins of tropical rainforests like the Amazon Congo and Mekong.
The Food and Agriculture Organization reported that in 2017, 34 percent of marine fisheries were classified as overfished. The Atlantic northwest cod fishery reduced populations to just 1% of historical levels by 1992.
Fish farming has been practiced since about 3,500 BCE in ancient China becoming increasingly important globally. Over 65 million tonnes of marine fish were captured in 2020 while some 50 million tonnes were farmed mainly freshwater.