These are an aquatic large group of vertebrates with gills for respiration and scales for protection and locomotion.
Fishes belong to the phylum Chordata.
Fishes are ectotherms means cold-blooded animals, which rely on the environment for temperature.
Sharks, skates, puffers, and seahorses are examples of fishes.
Kidney:
Kidney is the excretory organ of fish.
Kidneys are the excretory organ that filters liquid waste from the blood. They control water and salt concentration in fish bodies.
Fish has two types of kidneys namely the head kidney in which wastes pass through gills and the posterior kidney in which wastes pass through urinary pose.
In fish ammonia is the excretory waste that is easily soluble and removed by diffusion process across the body surface through gills and into the surrounding water.