Wednesday April 13, 2022

Bay Nature

Basking sharks can be over 30 feet long and are characterized by their enormous gill rakers and three-foot tall dorsal fins. But these mysterious, massive, filter-feeding cousins of the great white shark aren’t just a scientific curiosity – they also seem to be vanishing from California and the rest of the Eastern North Pacific. 

The National Oceanic and Atmospheric Administration conducted aerial surveys from 1962-2004 to monitor populations of commercially valuable fish such as sardines. The aerial surveys proved to be a valuable historic record for basking shark sightings, which are easily large enough to be spotted from the air.

Pilots reported their sightings to NOAA every year, and researchers have found that sightings decreased dramatically over the four decades of the survey. 

“The group size has declined, along with the decline in sightings,” said Alexandra McInturf, a postdoctoral scholar at Oregon State University and lead author on a new basking shark paper in the journal Frontiers in Marine Science. McInturf wrote the paper as a PhD candidate at UC Davis. “Prior to the 2000s, you could see up to 500 individuals in a group … and then after the 2000s, we were only seeing up to 10.” 

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