I
n ancient Rome, a holy man who inspected the
entrails of animals killed during sacrifices conducted
to predict the future was called a ‘haruspex’ –
literally, ‘one who looks at intestines’. According to
that definition, I could be called a haruspex too since
I’ve spent a fair amount of time opening fish stomachs
to see what they have been eating, thereby gaining
knowledge on their feeding behaviour and ecology.
Anglers can often be found peering into fish guts in
order to determine the best bait to use. Scientists also
want to know what those same fish eat, but for very
different reasons.
To a scientist, the term ‘trophic’ means relating to the
feeding habits of different organisms in a food chain or
web. By studying the diets of fish, they can construct
food chains or webs that show the various trophic
levels that species occupy, whether they consume
single-celled algae, zooplankton (eggs of fish, tiny
crustaceans, fish larvae or gelatinous animals), small
fish, large fish, squid, marine mammals and so on.
In this way, scientists can determine if different
species are specialist or generalist predators, whether
diets change with habitat or life-stage of the fish,
and whether a particular species feeds only during
the day or night. They can even calculate the totalDr Julian Pepperell has peered into
more than a few fish stomachs during
his career. In this in-depth article,
he details a major scientific study
that examined more than 3500 fish
stomachs from 10 species of pelagic
predators to determine how much
food each eats per day, how fast they
digest their food, and the important
role each species plays in the
marine ecosystem.AUTHOR: DR JULIAN PEPPERELL
PHOTOGRAPHY: DR JULIAN PEPPERELL; DOUG PERINNE;
TIM SIMPSON; AL MCGLASHAN; GEOFF JONES.WHAT’S
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