Scientists are puzzled by a mysterious occurrence taking place off the coast of San Francisco. Biologists said that hundreds of leopard Sharks are dying in the bay area. They are claiming that this is the largest die-off event concerning these creatures in the last six years.

A large number of leopard sharks along with halibuts and bat rays have been found dead along the shores of Alameda, Hayward, Redwood City, San Francisco, Oakland, Berkeley, and Foster City. Some of these dead sharks were also seen in Bolinas, Marin County. However, scientists are puzzled by this phenomenon.

Reason behind these deaths

Marine biologists opine that these sharks may be coming in contact with toxic waters from saltwater marshes, sloughs, and even from man-made lagoons that are present in Foster City and Redwood City. According to Sean Van Sommeran, executive director and founder of the Pelagic Shark Research Foundation, the leopard sharks make their way into the shallow water to mate during spring. It is during this time that both Redwood City and Foster City are closing their tide gates, essentially trapping the sharks in the shallow waters of the lagoon. Following this, fungal blooms on the stagnant water surface and cuts off the oxygen supply and poisons the sharks trapped under the water, which scientists believe is the main reason behind the deaths.

Previous leopard shark deaths

In 2016, a similar die-off was noticed and this year, the deaths have been the most numerous since 2011 – when nearly 1,000 of these sharks were reportedly found dead near Richardson Bay and Redwood Shores. This number was estimated to be much higher as scientists believe that many more dead leopard sharks did not wash up to the shores.

Similar cases have also been recorded back in 1967 when more than 700 sharks and rays were found near the coast of Alameda. Huge number of shark deaths took place each year between 2002 and 2006. The largest ever shark die-off event occurred in 2011. These sharks were fished regularly for consumption till 2011. However, after the largest die-off event, biologists warned people about the toxins, which may have entered the bodies of the leopard sharks.

These poisonous substances supposedly stain the fish’s blood and flesh, which when consumed by humans could also lead to adverse effects.

A dismal future?

Scientists wonder just how long the species can survive after suffering such deaths. Many posit that if this die-off occurs each year, then it may pose a huge problem for the entire leopard shark species because its numbers may fall drastically.