Is there a shark paradise in the Galapagos?
A new study of the marine life surrounding the Galapagos Islands reveals it contains the largest shark biomass ever reported, with researchers hoping their findings will push Ecuador to further enhance the protection of the Galapagos and its surrounding waters.
The study focused on the northern Galapagos islands of Darwin and Wolf, known to be a hotspot for sharks and other reef fish. Set apart from the rest of the islands within the Galapagos archipelago and 1,000 kilometres off the coast of Ecuador, these small and isolated islands -Darwin and Wolf measure just one and two square kilometres respectively- recently came fully under the protection of Ecuador’s no-take Galapagos Marine Reserve (where all forms of fishing are prohibited).
The Galapagos is unique in being at the crossroads of three major ocean current systems, bringing both cold waters from the west and southeast from Peru and warm water from the northeastern Panama Current. This confluence makes it a rich source for marine life and for food to attract predatory fish and other animals.
Using a diver-operated stereo-video system to gauge fish biomass surrounding Darwin and Wolf, the researchers from the Charles Darwin Research Station and the National Geographic Society were able to measure the biomass at 12.4 tons per hectare, with 73 per cent of it composed of sharks, primarily hammerheads (48 per cent) Galapagos sharks (19.4 per cent) and blacktip sharks (5.1 per cent).
This “inverted biomass pyramid” is typical of healthy marine ecosystems, say the study’s authors, and occurs when the top levels of the food chain have a much slower growth rate than their prey and where predators are able to top up their food intake from sources outside their area, as is the case at Darwin and Wolf where hammerhead sharks are known to make daily foraging excursions into surrounding waters.
“This study adds to the growing body of literature that highlights the ecological uniqueness and the global irreplaceable value of Darwin and Wolf,” say the study’s authors, who note that although the Galapagos Marine Reserve prohibits fishing, small scale illegal fishing of sharks within the reserve still takes place by locals keen to profit from the abundance of marine life. Not just sharks but other predatory reef fishes like leatherbass and the sailfin grouper are being caught.
“These species are highly prized by Galapagos artisanal fishermen,” say the study’s authors, “but their life histories (long lives, slow growing) make them extremely vulnerable to overfishing.”
Overfishing has caused shark decreases worldwide of over 90 per cent, with one in four species now threatened with extinction. But sharks are worth more alive than dead, according to studies on the economic benefits of ecotourism. A 2012 study of the Isla del Coco National Park in Costa Rica, a tourist haven for shark viewing, estimated that each hammerhead shark that visits the region brings in $1.6-million (USD) over its lifetime to the country in tourist dollars (compared to a paltry $195 if caught and sold at market).
For a Galapagos shark, the net present value is listed at a remarkable $5.4-million -roughly $360,000 per year- making them the most valuable living sharks on the planet.
While the establishment of marine protected areas such as the Galapagos Marine Reserve has been proven effective in helping marine ecosystems to recover from overfishing, in Canada, the David Suzuki Foundation has been critical of the federal government over the small fraction (less than 0.1 per cent) of Canadian waters that have come under such protection, stating that, “While Canada has committed to establishing these planning processes under the mandate provided in the Oceans Act and Oceans Strategy, these processes are not well-developed and suffer from lack of funding.”
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