The stretch of surf between Del Mar and Torrey Pines, long known as a nursery for juvenile great white sharks, has gone oddly quiet, researchers say. The young whites that used to cruise the shallow sandbars have largely moved on, and ocean scientists caution that the quieter skyline of dorsal fins does not necessarily mean a safer summer for San Diego swimmers.
Researchers told the San Diego Union-Tribune that the Del Mar to Torrey Pines aggregation held steady for about four years before the juveniles cleared out last year. As reported by The San Diego Union-Tribune, Shark Lab director Chris Lowe and collaborators have been tracking the animals with acoustic tags and watched the shift unfold as ocean conditions changed.
El Niño Could Bring Tropical Sharks North
NOAA’s Climate Prediction Center currently gives roughly a one-in-four chance that a very strong El Niño will develop later this year, a pattern that tends to warm coastal waters and shuffle marine life around. According to NOAA’s Climate Prediction Center, those warmer pockets have in past years let species that usually stay farther south move northward. During the strong 2015 El Niño, media reports documented hammerhead and other warm-water sharks showing up well beyond their usual range, at times prompting temporary beach advisories and closures, episodes chronicled by LAist.
What Researchers Are Watching
The Shark Lab at California State University Long Beach uses acoustic receivers and satellite tags to follow individual juveniles and map aggregation sites along the coast. A recent paper in Movement Ecology found that storms and rapid temperature swings can trigger temporary departures from nursery zones and quick re-formation somewhere else, helping explain why these shark hotspots can pop up one year and vanish the next. The lab’s methods and local monitoring networks, detailed by the CSULB Shark Lab, give researchers the telemetry tools to keep following those shifts.
For beachgoers, the message is a bit of a mixed bag. Experts, including Scripps doctoral student Jack Elstner and Shark Lab researchers, note that juvenile white sharks, typically about 4.5 to 10 feet long at this stage, mainly prey on fish and rays and are not thought to target people. At the same time, scientists point out that tropical species such as tiger and bull sharks “play by different rules,” and local reporting continues to push common-sense advice: swim in groups, listen to lifeguards, and report unusual sightings to authorities. That guidance shows up repeatedly in local coverage and expert commentary from outlets like 10News and in Scripps’ research notes…