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A concerning number of leopard sharks is washing up dead or dying in the San Francisco Bay.
A recent spike in the number of leopard sharks washing up dead or dying in San Francisco Bay has some researchers rightfully worried. Since the second week of March, the animals have been appearing along the shoreline in what are record numbers. The death toll could be in the thousands, and that sort of die-off is unprecedented, according to marine scientists.
Unexplained Mass Leopard Sharks Dead In San Francisco Bay, What’s Happening?
Autopsies performed on the animals’ bodies showed an extremely high level of toxins. Scientists at Pelagic Shark Research Foundation believe this is from trash, debris, and other chemical waste dumped into the San Francisco Bay.First the toxins enter the water supply. Then, the animals get trapped when tidal gates are closed before heavy storms. Although the leopard sharks can no longer leave the bay, yet the toxins continue to flow in, raising their concentration in the water.
The closing of the tidal gates also brings another problem. Since water cannot flow freely between the bay and the ocean, oxygen becomes depleted. Algae and fungal blooms tend to be more frequent, further consuming the oxygen dissolved in the water. The Foundation believes suffocation may also be part of what is leaving so many sharks dead or dying.
The rains also bring more toxicity with them as they wash the city, its roads, and its sewers, before then proceeding to drain into the bay as well. This again increases the concentration of the toxins, because it is closer to the discharge pipes and there is less water volume to fill.
During this period of the year, leopard sharks also tend to visit shallow waters on their way or while mating. As they gather in large numbers, this toxic infection can also spread more quickly among them. That is likely why so many young, otherwise healthy adults and even babies are among those found washed up on the shore.
These are the deaths that have scientists most worried about the future of the species. The last massive species die-off occurred some 6 years ago, in 2011. Scientists are concerned that the high number of dead of dying young sharks could affect the species’ continuity and survival.
Image Source: Wikimedia
