Realizing extra about what sharks eat is essential in managing how we work together with them, and a brand new research trying on the food plan of nice white sharks off the east Australian coast has revealed some shocking findings.
Based mostly on an in depth evaluation of shark abdomen contents, these apex predators spend much more time than we thought feeding down on the backside of the ocean mattress, moderately than gliding alongside the highest of the water, in search of prey.
Scientists seemed on the digested meals of 40 juvenile nice whites (Carcharodon carcharias), and found loads of fish species recognized for residing on the seafloor or hanging out buried within the sand down within the depths.
“The stereotype of a shark’s dorsal fin above the floor because it hunts might be not a really correct image,” says ecologist Richard Grainger, from the College of Sydney.
“This proof matches knowledge we’ve got from tagging white sharks that reveals them spending quite a lot of time many metres beneath the floor.”
Not solely can the food plan evaluation inform researchers extra about what nice white sharks wish to snack on, in addition they present a window into the migratory habits of those creatures: the place they’re consuming and why they could have to maneuver round.
On common, the shark diets consisted of 32 p.c mid-water ocean swimming fish (corresponding to Australian salmon), 17.four p.c bottom-dwelling fish (corresponding to stargazers), 14.9 p.c batoid fish that lurk on the seafloor (corresponding to stingrays), and 5 p.c reef fish (corresponding to jap blue gropers).
The remainder of the abdomen contents was made up of unidentified or much less plentiful teams of fish. Marine mammals, different sharks, squids and cuttlefish additionally often kind a part of the food plan of a juvenile nice white shark, in keeping with the researchers.
“This suits with quite a lot of different analysis we have completed displaying that wild animals, together with predators, choose diets exactly balanced to fulfill their nutrient wants,” says ecologist David Raubenheimer, from the College of Sydney.
The workforce in contrast their findings with different collected knowledge to try to perceive what sort of vitamins the sharks are in search of. That might in flip inform us extra about the place they wish to dwell, and the way human exercise can intrude with that.
As sharks grow old, they have an inclination to maneuver round extra, for instance – and tackle board extra fats of their food plan to assist energy these journeys. Weight-reduction plan and migration are intently linked, and whereas these new knowledge are primarily based on a comparatively small pattern, it may be mixed with motion information from nice whites which have been electronically tagged.
The researchers are calling for extra work to be completed to analyse the precise dietary composition of shark diets – not simply the calorific content material – in an effort to perceive the connection between their physiology, behaviour and ecology.
“Understanding the dietary targets of those cryptic predators and the way these relate to migration patterns will give insights into what drives human-shark battle and the way we will greatest defend this species,” says ecologist Gabriel Machovsky-Capuska, from the College of Sydney.
The analysis has been revealed in Frontiers in Marine Science.