Galápagos islands contain more introduced species than thought


Foreigners arriving despite stringent biosecurity protocols. Nick Carne reports.


Pristine no more: researchers have found more than 50 exotic species in waters around the Galapagos islands.

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Scientists thought there were five non-native aquatic species in the Galápagos Islands, but it turns out there are at least 53.

And that is “the greatest reported increase in the recognition of alien species for any tropical marine region in the world”, according to James Carlton from Williams College in the US, the lead author of a recent study published in the journal Aquatic Invasions.

To make matters worse, the marine biologists only examined a little bit of the UNESCO World Heritage Site, which lies roughly 960 kilometres west of the South American coast in the equatorial Pacific Ocean.

"This discovery resets how we think about what's natural in the ocean around the Galápagos, and what the impacts may be on these high-value conservation areas," says Carlton.

With colleagues from the Smithsonian Institute in the US and the Charles Darwin Foundation in Ecuador, he conducted field surveys on two of the larger islands – Santa Cruz and Baltra. They hung settlement plates from docks, suspended one metre underwater to see what would grow on them.

Most off the 48 additional non-native species they documented were sea squirts, marine worms or moss animals (also called bryozoans).

Thirty were new discoveries that could have survived on the islands for decades under the radar, 17 were species scientists knew lived on the Galápagos but had thought were native, and the final one had been collected in 1987 but not previously identified

Among the most concerning discoveries were the bryozoan Amathia verticillate – known for fouling pipes and fishing gear and killing seagrasses – and the date mussel (Leiosolenus aristatus), which researchers have already seen boring into Galápagos corals.

This has all happened, the researchers note, despite the islands having one of the most stringent biosecurity programs in the world.

International vessels entering the marine reserve may anchor in only one of the main ports, where divers inspect them. If non-native species are found, a vessel is requested to leave and have its hull cleaned before returning for a second inspection.

The problem, of course, is sheer weight of numbers. In 1938, just over 700 people lived in what was a pretty remote part of the world. Today, more than 25,000 people live on the islands, and nearly 250,000 visit each year.

  1. http://www.aquaticinvasions.net/2019/issue1.html
  2. https://nature.mdc.mo.gov/discover-nature/field-guide/bryozoans-moss-animals
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