How Hydropower Threatens Great Whites


Desire for hydropower -- electricity produced from machines that are run by moving water -- is driving an unprecedented global boom in related dam and turbine construction, but some marine life experts believe that the projects could pose serious threats to sharks and other aquatic species.

Great whites are of particular concern because tidal energy monitoring programs have not properly accounted for these apex predators, according to a recent investigation conducted by The Chronicle Herald.

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Shark prey numbers are also a concern for researchers. A favorite meal of both the sharks and tuna are eels, which can become mincemeat in hydropower machinery.

Martin Castonguay of Ottawa-based Fisheries and Oceans Canada told Discovery News, "As eels leave freshwaters, they sometimes have to pass hydropower dams and will often be killed going through the turbines."

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The Minas Passage in Nova Scotia, where seawater flows into the Bay of Fundy, is the site of multiple planned hydropower projects. Research conducted by Richard Karsten of Acadia University suggests that there are more than 7,000 megawatts of power potential in the Minas Passage. That figure balloons to 50,000 megawatts within the entire Bay of Fundy, computer models indicate.

A "Pre-Turbine Baseline Studies" report concerning the Minas Passage involved acoustic tracking of fish movements, but did not include monitoring of great whites. Authors Anna Redden and Michael Stokesbury of Acadia University, however, explained that earlier tagging identified striped bass, Atlantic salmon, Atlantic sturgeon, spiny dogfish and great whites at the Minas Passage.

"Of particular interest are white sharks," they added. "The white shark is a listed endangered species under the Species at Risk Act ... As with all other species, tagged fish represent only a small portion of the animals in a population. Given that >10 percent of the tagged endangered white sharks moved through Minas Passage, it is highly likely that large numbers of non-tagged white sharks also use this area."

John Chisholm of the Massachusetts Division of Marine Fisheries expressed a slightly different opinion about the number of sharks in the area. He told Discovery News that "to date >10 percent of acoustic tagged white sharks visited Canadian waters (but) only three visited the Minas Passage."

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The Bay of Fundy is just one area where hydroelectric firms and wildlife authorities are at odds. Environmental experts are worried about hydropower projects in Cambodia that have already involved the construction of several dams.

Emmeline Johansen of Conservation International's Asia Pacific Field Division told Discovery News that hydropower dams can threaten not only fish, but also humans, by a domino effect. She explained that dams can adversely affect fish migration and block 90 percent of sediment flows that are important for delivering nutrients farming regions.

CI created a film, "Hydropower Impacts and Alternatives" to highlight these and other threats to Cambodia's fisheries and food security. The film can be watched in its entirety online.

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Many sharks potentially could be affected, as waters off of Cambodia are home to such species as blacktip reef sharks, bull sharks and whale sharks.

Ironically, a shark -- the filter feeding basking shark -- has inspired the design for an efficient hydroelectric turbine.

It remains to be seen if the risks associated with hydropower can be fully addressed. The benefits are certainly many.

Renewable energies account for 20 percent of worldwide electricity production today, with hydropower contributing 80 percent of the total share. An expected 3,700 major dams may more than double the total electricity capacity of hydropower to 1,700 gigawatts within the next two decades.

As Klement Tockner, the director of the Berlin-based Leibniz-Institute of Freshwater Ecology and Inland Fisheries said, "When building new dams, it is important to follow a systematic management approach that considers the ecological, social, and economic consequences of multiple dams within a river basin."