We usually think of a food web as containing a gamy figure of target items at the bottom supporting relatively few predators that pose at the top . But what if it does n’t always have to be like that ? Researchers dive in the removed and near pristine water of French Polynesiahave found an ecosystemthat move around this on its head , where predators dominate and vastly outnumber their prey .
Beneath the waves surrounding Fakarava atoll in the Pacific , ecologists founda curious food web that is both unbelievable and unusual . In a tiny canyon they found a truly amazing sight : airless to 900 Rand sharks congregating in an area just 0.175 square kilometers ( 0.07 square miles ) in size of it . They had stumbled upon the highest ever concentration of gray-headed Witwatersrand sharks , which made up 78 percent of the sharks patrol the small transmission channel , dominating an ecosystem that is on the face of it paradoxical . There are too many predators being supported by the routine of prey Pisces live in the same pass .
Calculating how much food would be needed to plunk for such high numbers of shark , the researchers found they would call for over 90 tons of Pisces the Fishes to keep them exit , yet when they surveyed the canyon they expose that the fish biomass product was a measly 17 net ton per year , style below the shark ’s basic needs . So the obvious question then arose : how the sharks manage to survive live in such surprisingly high densities ? The answer , it seems , could give us a coup d’oeil at how a normal Rand should look in pristine seas , out from the influence of humans .
The grouper habituate the canyon to spawn . Laurent Ballesta / Andromede Oceanologie / Blancpain Ocean Commitment
It turns out that the channel in which the sharks haunt is also a favorite spawning ground for grouper fish , which visit every year between June and July to lie their orchis and reproduce . This , the researchers suggest , bring in the biomass from other local food web , concentrating it in one single small positioning for this shortsighted part of the twelvemonth , and allowing the shark to maintain such massive densities . It was previously believed that Pisces spawning aggregations only represented a pocket-sized food source for the nautical predator , but it now seems that instead they can bear out the integral food web , and maintain an inverted trophic pyramid .
“ Our findings confirm that in pristine remote coral reefs , shark can be numerous , sometimes even outnumber their prey at local scales,”explainsJohann Mourier , who coauthored the paper explaining this strange ecosystem , published inCurrent Biology . He indicate that as Gallic Polynesia represents near - pristine reefs , having escaped shark sportfishing and being protect since 2006 forming the humanity ’s expectant shark sanctuary , these types of food web could be the norm in fully operative unspoilt reefs .
And the sharks feast upon the grouper . Laurent Ballesta / Andromede Oceanologie / Blancpain Ocean Commitment/ Mourier et al . 2016
