Extreme Climate Survey
Science News is collecting reader questions about how to navigate our planet’s changing climate.
What do you want to know about extreme heat and how it can lead to extreme weather events?
“This is a complete shock,” says Anderson, of the North Carolina Division of Marine Fisheries in Raleigh. “We’ve never seen this before.”
A shark-eat-shark theory
Porbeagles (Lamna nasus) are large-bodied sharks that look like a cross between a great white (Carcharodon carcharias) and a short-fin mako (Isurus oxyrinchus) (SN: 11/10/22). They hunt fish including mackerel, cod and haddock. Some individuals have been known to reach lengths exceeding three meters, which is partly why it’s so surprising that an individual that was more than 2 meters long and a formidable predator in its own right should find itself on the wrong end of the food chain.
To be clear, scientists did not witness a great white shark attack the porbeagle. Rather, Anderson and colleagues pieced together the missing shark’s hypothetical demise using location, temperature and depth data received from tags that had been attached to the shark during a routine catch-and-release survey. These devices also allowed the scientists to track the porbeagle from Cape Cod, Mass., to Bermuda — a migration from which it would never return.
“All of a sudden, on March 24, that temperature increases even at 300 meters depth. And it stays high, even at 600 meters depth,” Anderson says. “That’s a very clear indicator to us that this tag is no longer in the water column attached to the porbeagle. It’s in the stomach of a larger predator.”
To figure out the identity of the killer, Anderson looked at a host of variables that only became available after one of the tags floated back up to the water’s surface, presumably after being excreted by the larger predator.
According to the transmissions, the temperature readings were warmer than…
Read the full article here