The shark-tastic days of 2016 may be coming to a close as many of the juvenile great whites that have been hanging around SoCal beaches are finally migrating south, says Chris Lowe, director of the Shark Lab at Cal State Long Beach.
Possibly spurred by dropping ocean temperatures, several juvenile sharks tagged with trackers by Lowe have forsaken California, most likely headed for warmer waters off Baja California. Lowe and his research team have been downloading data from the 45 sharks they have implanted with tracking devices. That process takes months, but early indications are that the sharks are behaving more like they did prior to the last El Nino event, which raised water temperatures and might have encouraged the youngsters to hang around Dana Point, Santa Monica Bay, Ventura and other local shark haunts.
“That seems to be the trend so far,” Lowe says. “Not only are we detecting fewer but people are sighting fewer sharks. With that said, sharks are still being sighted. They haven’t all left.”
Great whites are warm-bodied fish, meaning they can generate body heat sufficient to dive down to depths of 3,000 feet or cruise the waters of the Gulf of Alaska for prey. Yet, in the first few years of their lives, until they weight about 200 pounds, they tend to act more like cold-bodied sharks — they seem sensitive to changes in temperature. When the waters dip below 60 degrees, they’re likely to light out for southerly climes. When the waters reach 84 degrees, they’re likely to dive deep or head north, Lowe says.
“Once they’re a couple hundred pounds, they should be more temperature tolerant. This year we don’t totally know what to expect,” he says.
Typically, great whites will hang around SoCal only during the first winter of their lives. The warmer temperatures that resulted from the 2015 El Nino probably encouraged many young whites to overwinter in SoCal for a few years. Hence the presence of so many sharks in the 6-to-10 foot range for the past couple of years. Those fish were as old as four years.
“It was the first time we’ve seen so many adolescents,” Lowe says. Those adolescents were also acting more like baby sharks, in that they were kicking around very close to the beach and cruising in loose aggregations of a dozen or more sharks within a one-mile stretch of coast.
Once the sharks reach adulthood, they move farther afield in search of marine mammals, which are scarce in SoCal compared with the Central Coast, Northern California, and offshore islands in Mexico, California and elsewhere. That’s why we rarely see full grown whites in our near-shore waters.
Whatever happens with our resident juveniles, Lowe is convinced that the great white population in California is growing, based on his data and anecdotal information from people who’ve spent time on the ocean for the past half-century. That’s what you would expect, too, given protections placed on sharks themselves as well as their prey mammals.
Shark research is pricey, and despite the attention sharks get, funding is relatively scarce, Lowe says. Donations to the Shark Lab can be made here.