Tony Wu / Humphead parrotfish (Bolbometopon muricatum) shoal spawning in early morning, part of mass aggregation of thousands of fish. Caroline Islands, Palau.

Gary Bell/ Oceanwide / Painted Sweetlips (Diagramma pictum) in Slender Cardinalfish (Rhabdamia gracilis) school near Double-headed Maori Wrasse (Cheilinus undulatus), Great Barrier Reef, Australia

Gary Bell/ Oceanwide / Whitemouth Moray (Gymnothorax meleagris) being cleaned by Cleaner Wrasse (Labroides sp) juvenile, Christmas Island, Australia

Gary Bell/ Oceanwide / Double-headed Maori Wrasse (Cheilinus undulatus), Painted Sweetlips (Diagramma pictum), and Slender Cardinalfish (Rhabdamia gracilis) school, Great Barrier Reef, Queensland, Australia

Shane Gross / Pelagic thresher shark (Alopias pelagicus) cleaned by a Bluestreak cleaner wrasse (Labroides dimidiatus) at Monad Shoal off Malapascua Island, Philippines.

Shane Gross / Pelagic thresher shark (Alopias pelagicus) being cleaned by a bluestreak cleaner wrasse (Labroides dimidiatus) at Monad Shoal off Malapascua Island, Philippines.

SCOTLAND: The Big Picture / Cuckoo wrasse (Labrus bergylta) and Ballan wrasse (Labrus bergylta) on the wreck of Jayne, Shetland

Juergen Freund / Shoal of Sergeant majors (Abudefduf saxatilis) with various Wrasses (Labridae) feeding on the Sergeant major fish eggs, Raja Ampat, Indonesia.

Tim Fitzharris / Parrotfish (Scaridae), Wrasse (Labridae), and Sergeant Major Damselfish (Abudefduf saxatilis) school, Balicasag Island, Philippines

Tony Wu / Asian sheepshead wrasse (Semicossyphus reticulatus), male in white breeding colouration. Niigata Prefecture, Honshu, Japan. June.

David Fleetham / Cleaner wrasse (Labroides dimidiatus) swimming alongside Golden damsel (Amblyglyphidodon aureus) looking for parasites, Fiji, Pacific Ocean.

Alex Mustard / Harlequin sweetlips (Plectorhinchus chaetodonoides) cleaned by a pair of bluestreak cleaner wrasse (Labroides dimidiatus). South Atoll, Tubbataha Atolls, Tubbataha Reefs Natural Park, Palawan, Philipp...