Tripterygiid fishes (triplefins or threefin blennies) are a family of bottomliving blennioid fishes, inhabiting cold, temperate, subtropical and tropical sea shores and offshore islands. They are usually associated with hard substrates, mainly rock. The surface of the substrate is ideally rough, so that triplefins can adhere to it using their pelvic fin rays. Most species live subtidally on rocky or coral reefs or in intertidal rock pools; a few occur deeper, on the continental shelf and other slopes down to at least 550 m depth. Very few species live in fresh water. The use of modern collecting techniques like rotenone collections has revealed that the Tripterygiidae is a large and abundant group. A total of 32 genera and 164 species is currently known worldwide (Table 1.2.1). All species are small; the largest does not exceed 150 mm SL (Blennodon dorsale, New Zealand), while the smallest attains 20 mm SL as its maximum size.