Ichthyology

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Ichthyology covers a diverse range of body forms and sizes.

• top: whale shark and Paedocypris progenetica
• bottom: European river lamprey

Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 35,800 species of fish had been described as of March 2025, with approximately 250 new species described each year.^{[1][citation needed]}