To date, science recognizes fish as the most diverse and populous group of vertebrates present on Earth, with over 23,000 species.
Based on fossil records, it has been determined that fish first appeared on our planet approximately 500 million years ago, long before dinosaurs and many other prehistoric animals.
Fish vary greatly in size and weight. For instance, the blue whale is the largest fish, measuring between 25-35 meters in length and weighing between 140-190 tons, while the smallest fish, Paedocypris progenetica, was recently discovered on the island of Sumatra in Indonesia and in the Borneo region of Malaysia, with adults measuring only 7.9 mm in length and weighing no more than 1.5 grams.
Another remarkable aspect of fish is their ability to thrive in a wide range of habitats, including some species that can survive in freezing environments or in hot springs with temperatures between 70-80°C.
NGUYEN SINH
