Shark pups do not reach their full physical potential in environments impacted by human-induced factors such as the climate crisis, according to a study.
Jodie Rummer and her colleagues at the James Cook University in Australia compared the foraging behaviour and health conditions of newborn reef shark populations in two places.
One was St Joseph, an uninhabited, remote and small atoll in the outer islands of Seychelles a country in East Africa in the Indian Ocean -- where no environmental changes happened at the time of the study.
Another was Moorea, a popular tourist destination in French Polynesia and a place that is still recovering from a loss of up to 95 per cent of its live coral cover from about five years before the study started.
The researchers captured and measured a total of 546 young sharks during the four year period of the study, and found that the amount of fat reserves the pups had varied between the locations.
According to the study, published in the journal Scientific Reports, even if the shark pups are born larger, heavier, and better conditioned in Moorea, they lost their physical advantage over the pups in St Joseph.
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"At birth, newborn sharks receive extra fat reserves from their mother," said Ornella Weideli, lead author of the study and PhD student at the Centre de Recherches Insulaires et Observatoire de l'Environnement (CRIOBE) in France.
Weideli added that the fat reserves helped the pups sustain during the first days and weeks after birth.
"The 'energy boost' is important, as sharks are independent from their mothers from the moment they are born," she said.
According to Rummer, bigger shark mothers gave birth to bigger pups which, she added, was what happened in Moorea.
"But that doesn't necessarily mean the babies will eat and grow quickly after that," she said.
The bigger babies from Moorea, the study noted, soon lost their advantage in size, weight, and condition.
"Against our expectations, the larger pups from Moorea that received greater energy reserves started foraging for food later in life, which resulted in considerable declines in their body condition," Weideli said.
Despite being smaller and lighter for their size, the researchers noted that the pups from St Joseph started foraging for food earlier in life, and became more successful predators than their Polynesian counterparts.
According to the authors, the bigger pups lost their physical advantage as Moorea was experiencing a degraded quality and quantity of prey.
This, they said, also compounded with human-induced stressors such as coastal development, over-fishing, and the ongoing climate crisis.
Earlier this year, in Moorea, the corals bleached during very hot temperatures after the completion of the study, creating an even bigger hurdle for the pups to survive, the researchers cautioned.
The researchers advised that mitigating human-induced stressors, especially during the season when sharks nurse their young ones, was key to protecting the species and the ecosystems they support.