Page 71 - BBC Wildlife Volume 36 #05

Camouflage groupers
spawn in vast numbers
on the Fakarava Atoll.

GROUPER GROUPS: MASS SPAWNING

Wrasse aren’t the only marine fish University, who have studied the
to engage in mass spawning. Up to aggregation for years, discovered that
20,000 camouflage groupers gather this ecosystem is flipped upside-down.
to spawn each June and July at a Normally a food web has more animals
particular spot on Fakarava Atoll in at the base, but at Fakarava the reef is
French Polynesia, as seen in BBC by contrast top-heavy with predators;
One’s Blue Planet II. Hundreds of grey the super-abundant groupers support
reef sharks also show up for a feast. the greatest density of sharks known
Researchers at Sydney’s Macquarie anywhere on the planet.

are emerald green. Cuckoo wrasse are highly inquisitive
and often follow divers around. Male and female corkwing
wrasse pair up during the May–July breeding season. The
male, with electric blue and orange scribbles on his face,
gathers up a ball of filamentous algae and wedges it in a
crevice on a rocky reef. The female then lays her eggs in this
nest and the male stands guard.
But of all the wrasse, humpheads are by far the biggest.
Few species of bony fish on coral reefs come close in size
(some cartilaginous fish – sharks and rays – can be bigger
and heavier). Records show humpheads may reach over 2m
in length, weigh 190kg and live for at least 30 years. Sadly,
such immense proportions and slow maturation make them
highly vulnerable to overfishing. Compared to smaller, faster-
growing species, a population of these big fish won’t bounce
back when numbers have been depleted.

A MEAL FIT FOR A KING… AND NOW HIS SUBJECTS
Across their range in the Indian and Pacific Oceans
humphead wrasse have traditionally been sacred fish –
reserved for royal feasts on the Cook Islands and only eaten
Above: the magic
moment when a by tribal elders in Papua New Guinea. More recently, though,
pair spawns. commercial fishing has taken over. Humpheads are now
Left: juveniles hunted and transported alive to Asia to supply expensive
can be identified seafood restaurants. Facing this growing threat, they’re now
by their greenish classified as Endangered.
colour and
two black lines A major aim of my trip to Swallow Reef had been to
running behind investigate another aspect of the humphead’s biology that
the eye. could magnify its risk of extinction. It gathers to spawn
at predictable times in the same places, forming obvious
targets for fishers. Other reef fish, such as the Caribbean’s
Nassau grouper, have historically been hit hard when their
spawning aggregations were depleted by overfishing.
BBC Wildlife 71