Leopard sharks dying by the thousands have been reported in the San Francisco Bay area of California, alarming environmentalists. The die-off of the leopard sharks in such high numbers, the highest seen since 2011, is being blamed on toxic runoff from debris and chemicals dumped into the waters of the San Francisco Bay.
According to the San Francisco Chronicle, in 2011, there were over 1,000 dead sharks counted in Marin County, along Richardson Bay, and in the vicinity of the Redwood Shores Lagoon. Researchers believe that they now know some of the main contributing factors behind the most recent leopard shark deaths.
Tech Times reported that dead sharks in the hundreds have been washing up on beaches stretching from Bolinas to San Mateo. According to researchers, since the second week in March, the dead sharks have been washing up along the shorelines of many cities in California, including Oakland, Redwood City, Berkeley, San Francisco, Alameda, Foster City, and Hayward.
Experts have said that the deaths of the sharks in the San Francisco Bay area are the result of sharks eating “poisoned food in stagnant salt waters.” Among the dead sharks, researchers have found a shockingly high number of newborn sharks and even mature adults. The leopard shark is the San Francisco Bay area’s “most abundant shark.”
According to the Pelagic Shark Research Foundation, drains and waterways used to dispose of chemical waste and trash caused poisonous substances to flow into the San Francisco Bay, contributing to the deaths of the sharks. Adding to the problem, when the tide gates inside San Francisco Bay have been closed in order to prevent flooding, it has also trapped many sharks in the bay and led to their dying due to the toxic runoff.
Near the tidal gates of the Redwood City and Foster City lagoons, the leopard sharks ingested even more toxins in the food they consumed in the area’s “stagnant saltwater marshes.” In the estimation of the California Department of Fish and Wildlife’s senior fish pathologist, Mark Okihiro, “several hundred sharks have already died.”
Another factor contributing to the deaths of so many leopard sharks is that they mate and breed in the shallow waterways in the San Francisco Bay area in the spring and summer months. This places them in the very waterways that have been most susceptible to the poisonous runoff, tainting the sharks’ food supply.
When the tidal gates are closed, it contributes to the salty marsh waters becoming stagnant. This lead to the development of fungal blooms which exhaust the limited amount of oxygen in the shallow waters, further poisoning the sharks and other fish there.
According to the Los Angeles Times, one of the other species of fish that have experienced a large die-off in the San Francisco Bay area has been bat rays, a type of sting ray. This year’s “epic storms” have been yet a further contributing factor, washing pent-up chemical waste and debris into the bay and poisoning the marine creatures that live there.
By contrast, sharks off the coast of California “are thriving.” That is because they have sufficiently warm enough waters and abundant food sources available to them. The waters off the coast of Southern California are the perfect habitat at this time of the year for baby white sharks, as the waters there are warm, but do not get above 80 degrees, a temperature that is unsuitable to their health and well-being.
This year, some areas off the coast of Southern California that have seemed popular with sharks include Belmont Shores, Santa Monica and Ventura. Harbor patrol deputies at Dana Point reported spotting four great white sharks at the surf line that were six to eight feet in length.
This year, leopard sharks in the San Francisco Bay area have been dying off at an alarming rate, and the final count might be in the thousands. Researchers have pointed to several potential contributing factors resulting in the deaths of the sharks, likely all related to the poisonous runoff of chemical waste and debris into the bay and tide gates being closed to prevent flooding due to the storms the region has been experiencing in 2017. The closure of the tide gates concentrated the poisonous wastes and trapped the sharks and other fish, like the bat rays, contributing to their deaths.
By John Samuels
Photo Courtesy California Department of Fish and Wildlife