Scientists suspect warming temperatures might explain the animals presence in Californias Monterey Bay

A group of young great white sharks has taken up residence along the central coast of California, enthralling beachgoers, residents, local media outlets and scientists.

Marine biologists are working to understand why the sharks the largest predatory fish in the world have ventured up to Californias Monterey Bay.

The juvenile great whites typically reside in the balmy waters of southern California, near the US-Mexico border. But the fish have increasingly wandered north in the past few years, leading to frequent sightings in the Monterey Bay since 2014.

Scientists suspect the warming temperatures of the ocean may play a role in the sharks surprising movements.

White sharks are endotherms they have a warmer internal temperature, which makes them more like mammals than fish, said Sal Jorgensen, a senior research scientist at the Monterey Bay Aquarium who studies white sharks in the Pacific Ocean. Especially when theyre first born, they have to stay in a Goldilocks temperature range thats not too hot and not too cold.

Along with researchers at local universities, Jorgensen has been working to tag and track the white sharks, to better understand how these large, ancient marine predators are coping with a changing climate. He said warming ocean temperatures driven by the climate crisis could have attracted the sharks to regions that were previously too cold for comfort.

Dr
Dr Salvador Jorgensen, a senior research scientist at the Monterey Bay Aquarium, in position to deploy an electronic tag on a juvenile white shark in Monterey Bay. Photograph: Monterey Bay Aquarium

Starting in 2013, a curious mass of warm water that scientists call the Blob moved through the Pacific, triggering ripple effects throughout marine ecosystems. Years of El Nio that followed kept surface temperatures warm and likely tempted the sharks to stay on even longer especially in a pocket of warmth near the famed surfing beaches of Santa Cruz, California.

An abundance of fish likely kept the young predators well-fed and content. And we know that these sharks really imprint on an area, Jorgensen said. Once they have a favorite hunting area they return to that same spot year after year for decades. Fully matured sharks, who annually migrate 1,200 miles offshore to whats known as the White Shark Caf, return to their coastal birthplaces in order to have children of their own.

Jorgensen said he and other researchers are still working to confirm their hypotheses about how changing conditions are affecting shark behavior. They plan to closely watch the Monterey white sharks in the coming years and see if theyll stick around. It is possible that this area could become a new birthing area, he said.

The group of juveniles currently hunting in Monterey Bay has sparked a number of shark warnings. Local media outlets have sent reporters up in helicopters to document the groups movements. And tour boat companies are starting to offer shark-watching trips.

I think theres this little kid inside a lot of us that gets so excited at the thought of seeing a real-life great white, said Megan Petersen, a naturalist who conducts tours for a charter boat company called Santa Cruz Whale Watching.

It seems like some of them are really curious about our boats so theyll swim right up to the boat, just a few feet away, added Petersen, who started leading white shark expeditions earlier this month. Theyre just breathtaking.

Experts say the group poses little danger to humans. Adult white sharks, which can grow up to 20ft long, are apex predators that hunt marine mammals like sea lions and seals. Juveniles are less than half as big and feed exclusively on smaller fish and squid. So theyre generally not a threat to humans, and theyre pretty docile, Petersen said.

Monterey
Monterey Bay tour boat companies are starting to offer shark-watching trips. Photograph: Sean Van Someran/Santa Cruz Whale Watching and Stagnaro Charter Boats

In fact, great whites are have been suffering from a major image problem, said Taylor Chapple, a marine biologist at Stanford University who in addition to researching sharks has been working to rehabilitate their reputation of being mindless killers. In my mind, theyre more majestic than scary, Chapple said. Theyre sort of like those giant dog breeds like Great Danes or something they just saunter around the ocean. Its like they know their place in the world. They know what theyre doing.

Sharks have been roaming the seas for hundreds of millions of years, notes Jorgensen. When I began to realize that they are no longer the top predators that humans are endangering them, even though weve been on this earth for just a tiny flash of time, I felt I had to do something to understand them better and help them survive.

Its not uncommon for the giant fish which can live up to 70 years or more to get tangled in fishing nets, or poached for their valuable fins. Overfishing could deplete their food sources and ocean pollution imperils their habitats.

Various protections enacted since the mid-1990s in California have helped local white shark populations thrive, though scientists are still working out precise population sizes and trends. A 2011 study estimated that 219 adult great whites lived off the central California coast. The species is categorized as vulnerable on the IUCN Red List.

Im cautiously optimistic that thanks to bans on net fishing, and other protections, their numbers are increasing, Jorgensen said. But we know much less about what happens once they leave our sanctuaries.

Source: http://www.theguardian.com/us

 

Recommended For You



Like it? Share with your friends!

0 Comments

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.