ATLANTIC ROCK CRAB, ÍSAFJÖRÐUR

© 2024 Elisa Debora Hofmann

The Atlantic rock crab came from North America to Iceland in the ballast water of ships. In recent years, it has spread in the warming seas around the country and reached the Westfjords. It outcompetes native crabs and may affect other species too.

A small sign in the port of Ísafjörður indicates what most people probably overlook: researchers have placed a trap here to catch Atlantic rock crabs. While carrying the Atlantic in its name, the crab is not native to Iceland. Originating from the East coast of Canada and the United States, it has travelled to Iceland most likely in ballast water of ships that connect a globalized world [28]. Warmer seas have facilitated the spreading of the crab around Iceland, including now also to the Westfjords [29]. The crab’s arrival will have consequences for the marine ecosystem, even though the precise impacts are still unknown [Interview 2], [30].

The Atlantic rock crab is not the only newcomer in the waters of the Westfjords. Pink salmon is another alien species that has been on the rise [31]. Every two years, they come to Icelandic waters and run up the rivers to spawn. The species, native to the Pacific, has spread to the North Atlantic from the White Sea where the Soviet Union introduced it in the second half of the 20^th century. While there are signs that the species may establish itself permanently in Iceland, knowledge about its local ecological impacts is limited [32]. With more connections across the globe and rising sea temperatures, rock crab and pink salmon will not be the last species to find their way to Iceland and the Westfjords [33].

Scientists seek to monitor the new species. They catch Atlantic rock crabs, count and measure them, record any diseases they have, analyze them as biological indicators for heavy metal concentrations, and assess their impacts on their prey and other marine species [Interview 1, 2]. One recent observation is that the rock crab outperforms native crabs, such as European green crab and spider crab [29]. However, pinning down population trends and ecological effects takes time. According to Icelandic law, a species cannot be classified as invasive until its negative effects have been established scientifically—and consensus on which species are invasive is often lacking [34]. Once science has gathered enough data to reach a verdict, it may already be too late to manage invasive species effectively. Science then becomes restricted to understanding ecosystem changes in retrospect [Interview 2].

If science cannot stop invasive species, it can help dealing with them in creative ways. The Atlantic rock crab is tasty, making it a potential fishery product. Researchers are collaborating with local fishers, considering their knowledge and economic needs, to analyze the crab’s potential to add value to small-scale fisheries [35]. Fishing an invasive species for consumption can have several advantages. It can be an additional source of income for fishers outside of the quota system, deliver new data for scientists, and help manage the species [Interview 2]. However, it also creates economic interests that will depend on continued use of the new species—heralding what may be an unavoidable future with the Atlantic rock crab.