Fishes are the most diverse of all vertebrate groups.

Fish have breathing, feeding, sensory, locomotion and reproductive structures that make them specially adapted for life in water.

Many groups of fishes are among the most endangered vertebrates.

Collection-based research provides crucial scientific underpinning for conservation policy and planning.

Cladistics is a method of classifying living things by reconstructing their evolutionary relationships. It uses shared derived characteristics—features that evolve for the first time and are passed on to all an organisms' descendents—to establish relationships. Cladistics is the method used in modern systematics.

Systematics is the branch of Biology that discovers and classifies the diversity of life, both living and extinct. When studying a group of organisms, a systematist typically looks for evidence (in the form of shared derived characteristics) that supports evolution from a common ancestor.

In biological terms, success is based on different criteria, These include how diverse a group of organisms is (for example, there are 24,000 ray-finned fish species compared to about 820 species of sharks and rays), how long a species has lived on Earth, the development of specialized adaptations and how many individuals belong to a species.