Re­searchers dis­cover reef sharks pre­fer bite-size meals

Port Douglas & Mossman Gazette - - SPORT -

SHARKS have a rep­u­ta­tion for hav­ing vo­ra­cious ap­petites, but a new study shows that most coral reef sharks eat prey that are smaller than a cheese­burger.

Re­searchers from James Cook Univer­sity’s ARC Cen­tre of Ex­cel­lence for Coral Reef Stud­ies ex­am­ined stom­ach con­tents of reef sharks and con­ducted chem­i­cal analy­ses of shark body tis­sue to find out what they had been eat­ing.

Lead au­thor, Dr Ash­ley Frisch said that af­ter pump­ing a shark’s stom­ach to iden­tify the con­tents of its last meal, the most com­mon thing to find was in fact, noth­ing.

“We were sur­prised to find a broad range of small prey items such as fish, mol­luscs, sea snakes, crabs and more of­ten than not, noth­ing at all”.

“These re­sults sug­gest that reef sharks eat small meals in­fre­quently and op­por­tunis­ti­cally,” Dr Frisch said.

To un­der­stand what the sharks were eat­ing over longer pe­ri­ods, the re­searchers an­a­lysed shark body tis­sue.

“Al­though black-tip, whitetip and grey reef sharks have long been thought of as top preda­tors, we found that the chem­i­cal struc­ture of the sharks’ body tis­sue ac­tu­ally matched closely with that of large reef fishes such as groupers, snap­pers and em­per­ors,” Dr Frisch said.

“This re­sult tells us that reef sharks and large fishes have a sim­i­lar diet, but they don’t eat each other.

So rather than eat­ing big fish, reef sharks are eat­ing like big fish.”

Un­der­stand­ing ‘who eats who’ on coral reefs is im­por­tant in help­ing sci­en­tists bet­ter pre­dict how changes in one pop­u­la­tion im­pact an­other.

Co-au­thor of the study, Dr Justin Riz­zari, said the re­search changes how sci­en­tists think about food webs on coral reefs and acts as a re­minder that large, con­spic­u­ous preda­tors are not al­ways at the top of the food chain.

“The top preda­tors are tiger sharks, ham­mer­head sharks, or peo­ple,” Dr Riz­zari said.

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