In California’s greatest conservation success story, better water quality and intentional ecosystem management have brought great white sharks back in significant numbers to waters off the California coast.
“Great white shark” is the common name for the species scientists usually refer to as “white sharks.” A study of the migrations of these sharks has lead to the discovery of two nurseries for baby white sharks, one along the Southern California coast and another in the Baja area and Dr. Christopher Lowe, California State University, Long Beach Professor of Marine Biology says that white sharks should not be considered threatened or endangered at this time.
Great white sharks pre-date dinosaurs in evolutionary history and have evolved to be warm-blooded. They give birth to 2 to 14 live pups. Babies average a little less than six feet in length, growing in the first year to over 11 feet. Adults are 11.5 to 12 feet in length.
Dr. Lowe discussed the 10-year research project that documented this success story at an April 11 Lunch and Learn talk at the California Science Center (CSC) in Los Angeles. Havasi Wilderness Foundation Director Sandor “Alex” Havasi and Assistant Director Marilyn Fordney were invited to attend the talk. Dr. Lowe explained that biologists from the Monterey Bay Aquarium and the Southern California Marine Institute partnered with Cal State University, Long Beach to learn the migrations of juvenile great white sharks in waters off Southern California and Baja California.
Today, when a white shark is caught in an off shore net, fisherman must report the incident. To facilitate research and to protect the shark, a tag is put on the captured shark’s fin and it is released. These hi-tech devices transmit data via satellite, allowing researchers to learn where they migrate in the winter and where their nurseries are located.
Marine stock and marine mammals declined in California’s coastal waters when the use of entangle nets began in 1949. But in 1994, Proposition 132 banned the use of the entangle nets in certain waters and near shore gillnets were banned in 1999. Since that ban, researchers have seen an increase in numbers of white sea bass, giant black sea bass, leopard shark, and soupfin shark. Sea lion populations have been on the upswing since their lows in the 1920s. Their population is currently growing at an explosive rate of 6.5% annually, creating an attractive food source for large predators.
Cleaner waters have also helped the white shark population rebound. Presently there is wastewater treatment along the entire Southern California coast, though urban runoff and trash remain a problem. Many contaminants have been banned, such as DDT which has been banned for over 40 years, and environmental levels are decreasing. Other important conservation measures that have contributed to growth in the number of white sharks along with many species of fish include the Clean Air Act of 1970 and the Clean Water Act of 1972.
By being careful to minimize the human impact on the environment, this species that predates humans by tens of millions of years has been able to make a comeback off California’s coast in just the last few decades.