The Mystery of the Disappearing Gobies
Even as marine scientists have been cautiously rejoicing
over the recovery of corals that had been through bleaching events on the Great Barrier Reef in the late 1990s,
a new finding suggests that the almost unnoticed tiny
gobies that were once found everywhere in the niches of
the reef are not coming back.
From sizes of less than an inch to about 1. 75 inches
(25-45mm) in length, the gobies (Family Gobiidae) are
so small and cryptic they often go unseen to the casual
visitor—but they make up almost half of all the fish life,
as measured by number of individuals, on the reef, says
ichthyologist Professor David R. Bellwood of the ARC
Centre of Excellence for Coral Reef Studies and James
“These fish may be tiny, but they are very important.
They are telling us that the world has changed, and in
ways we do not understand. That we may not be able to
manage things as well as we hoped,” he says.
“In 1998 there was a major coral bleaching event
that affected some 40 per cent of corals across a huge
area of the reef. After some years, quite a lot of the coral
has recovered—and looks more or less as it once did.”
30 GENERATIONS WITH NO RECOVERY
“But the gobies have not come back. Something is not
right if the fastest breeders of the reef are still missing.
Overall, the coral fish fauna are still in a degraded state—
after 30 generations.” In a published paper several years
ago, the abundance of the Green or Broadbanded Clown
Goby, Gobiodon histrio, for example, had diminished 67
percent seven years after the bleaching event. (Bellwood,
et al. 2006.)
Prof. Bellwood has devoted almost 20 years to the
study of what many might imagine to be the least significant of fish on the reef. He feels they may be far more
important than might appear, as indicators of the health
status of the Reef.
“Gobies are among the Reef’s most plentiful species.
They live fast and die young, in vast numbers. Many big
reef fish live ten years or more: a typical goby lasts just
100 days. Everything eats them—they are the ‘Tim Tams’
(chocolate bisquit snacks) of the Reef. For every ten that
wake up in the morning only nine go to sleep at night.”
Studying something as small as gobies is not easy.
Usually it consists of encasing a coral bommie in a large
mosquito net, and then meticulously collecting anaesthetized fishes. Comparisons of goby populations over
many years before and after bleaching, even in reefs with
apparently healthy coral, shown signs of major change.
“Because their generations turn over so quickly, gobies provide a highly sensitive indicator of changes that
may be taking place, far more so than the longer-lived
species, like large fishes or turtles.
to create a
GREEN MARINE ALGAE
BROWN MARINE ALGAE
RED MARINE ALGAE