Galapagos Islands Wolf and Darwin home to largest shark biomass in the world
Overfishing has reduced biomass of most sharks and other large predatory fishes worldwide by over 90%, and even remote locations have been severely impacted. The islands of Darwin and Wolf in the far north of the Galapagos Marine Reserve though, are known for their large shark abundance, making them a global scuba diving and conservation hotspot.
In a study published this week in the journal PeerJ, scientists from the Charles Darwin Research Station (CDRS) and the National Geographic Society revealed that the islands are home to the largest shark biomass on the planet reported to date at 12.4 tons per hectare.
Despite this, the abundance of reef fishes around the marine reserve, such as groupers, has been severely reduced because of unsustainable fishing practices. Although Darwin and Wolf are within the reserve, they were not fully protected from fishing until March this 2016. Given how important the Galapagos are to Ecuador’s dive tourism industry and to the well-being of these top predators, the scientists hope that the current protection will ensure the long-term conservation of this marine and diving hotspot.The shark biomass divers collected data using stereo-video surveys at seven sites at Darwin and Wolf islands. These surveys are considerably larger than those reported at Costa Rica’s Cocos Island National Park and the Chagos Marine Reserve in the Indian Ocean, home to the world’s next largest shark biomasses.
The establishment of marine protected areas, especially no-take areas where all forms of fishing are prohibited, have been shown to be one of the most successful management tools to confront global ecosystem degradation.
The Galapagos Islands are known worldwide for their iconic terrestrial fauna and flora, due in large part to Charles Darwin. However, the underwater Galapagos remains under-studied and largely unknown compared to terrestrial ecosystems.
Galapagos is the only tropical archipelago in the world at the cross-roads of major current systems that bring both warm and cold waters. From the northeast, the Panama Current brings warm water; from the southeast the Peru current bring cold water; and from the west, the subsurface equatorial undercurrent (SEC) also bring cold water from the deep. The oceanographic setting surrounding Galapagos results in a wide range of marine ecosystems and populations, that includes from tropical species like corals or reef sharks to temperate and sub-Antarctic species like the Galapagos fur seal (Arctocephalus galapagoensis
) or the waived albatross (Phoebastria irrorata
Nearly 73% of the total fish biomass around Darwin and Wolf was accounted for by sharks, primarily hammerheads (Sphryna lewini
48%), Galapagos (Carcharhinus galapagensis
19%), and blacktips (Carcharhinus limbatus
Photo by Enric Sala/National Geographic A group of hammerhead sharks swims over the sandy seafloor populated with garden eels at Darwin Island. These sharks are known for their ability to make sudden and sharp turns as the unique wide-set placement of their eyes allows them a vertical 360-degree view, which is ideal for stalking their prey.