How to stop invasive underwater species

2015-05-28 15:30:00
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When creatures from the Red Sea stray into Mediterranean waters, the results can be lethal. Red-Sea pufferfish colonising the eastern Mediterranean are so poisonous they kill about one in ten people who unwittingly eat them. Summer swarms of a stinging Red-Sea jellyfish, stretching as far west as Italy, force beach closures and clog intake pipes at desalination and power plants. Rabbitfish from the Red Sea devour Mediterranean algae that would otherwise feed native fish.
Egypt is enlarging the Suez Canal to double its ship capacity, and scientists worry that more Red-Sea creatures will then make their way into the Mediterranean. How might they be stopped?
Electrifying water is one option. Bigger animals feel the jolts more than small fish; the voltage builds gradually, so fish turn around before getting injured or killed. A spot in the Puntledge River near Courtenay, British Columbia, has been electrified to prevent seals from decimating juvenile salmon.
Many fish dislike turbulent bubbles, so bubble-curtains are increasingly being implemented by pumping air into underwater pipes pierced with tiny holes. To make them look scarier, they can be illuminated with erratic flashes of light. Noise in obnoxious rhythms and pitches completes the effect. This underwater disco in the Sacramento-San Joaquin river delta keeps Chinook salmon out of a pumping station in Tracy, California.
Water itself can be a barrier. Saltwater fish don’t swim through the Panama Canal because it traverses Lago Gatún, a freshwater lake. Some scientists say that the Suez Canal should contain such a salinity barrier. After all, for about eight decades after the canal’s opening in 1869, few creatures made it through, thanks to the extra salinity coming from salt in the ground. Even brine pumped from a desalination plant could do the trick.
Egypt says it will take “adequate measures” to limit the passage of invasive species. But what that means is not yet clear. And the digging at Suez is almost done.
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