Fish are a diverse group of cold-blooded, water-dwelling vertebrates found in almost every aquatic habitat, from freshwater rivers and lakes to the deep sea. They typically have streamlined bodies, scales, fins, and gills, which allow them to move efficiently and extract oxygen from the water.

Fish reproduce in various ways, from laying eggs to giving live birth, and they play essential roles in aquatic ecosystems as both predators and prey.

Fins are key for movement, stability, and steering. Fish typically have dorsal, pectoral, pelvic, anal, and caudal (tail) fins.

Fish have various body shapes and colours depending on their habitat. Reef fish, for example, are often brightly coloured to blend in with corals, while deep-sea fish may have bioluminescent organs.

Some species are adapted to extreme environments, such as the deep-sea gulper eel, which can survive in high-pressure, low-light conditions.

Fish are the most diverse group of vertebrates, with over 34,000 recognised species worldwide.

Some popular fish types include:

Saltwater Fish: These include clownfish, tuna, marlin, and sharks.

Freshwater Fish: These include catfish, trout, and bass.

Coral Reef Fish: Like parrotfish and angelfish.

Fish are part of the phylum Chordata and are generally divided into three major groups:

Jawless Fish (Agnatha): Primitive fish, like hagfish and lampreys, lacking jaws and paired fins.

Cartilaginous Fish (Chondrichthyes): Fish with skeletons made of cartilage, such as sharks, rays, and skates.

Bony Fish (Osteichthyes): The largest group, including most fish species. These fish have bony skeletons and include species like salmon, cod, and tuna.

Fish vary significantly in size, shape, and behaviour, and their adaptability has made them one of the most abundant and varied animal groups. They play crucial roles in ecosystems and are a significant food source for humans and other animals.

Overfishing, pollution, and climate change have threatened many fish populations, impacting both biodiversity and food security. Sustainable fishing practices and marine conservation are essential to preserving fish diversity.