Category Archives: Profiles of an Alien
Reasons for deliberately introducing novel species vary, from their aesthetic appeal to a boost they may provide the economy with. Using them for biological control is another, and it has led to some of the world’s most infamous biological invasions. Today we look at the Asian Ladybeetle, which Norwegian farmers were keen on importing into the country to use to control pest species that were damaging local crops.
Fur farming isn’t a topic we’ve had much cause to touch on so far in this series. But today, we look at a species that was introduced specifically for that purpose, whose presence in Europe is disliked by ecologists and animal rights activists alike.
Last Monday, I wrote about how climate change can facilitate the spread of non-native and invasive species. Today, we look at a species that whilst problematic now, could spread further throughout Norwegian waters as temperatures rise.
The last time we looked at an ocean-dweller in this series, we saw that while some species may not be great for ecosystems, they can provide an obvious benefit to other aspects of the region, in this case the fishing industry. The Pacific oyster (Crassostrea gigas) was also introduced intentionally for cultivation and is now on the verge of becoming a major problem in Norwegian waters.
What are they?
Because of its tolerance of most environments, the Pacific oyster has become the most widely cultivated oyster in the world, and thus one of the most widely distributed alien species in the world. Originating from the North-West Pacific, around Japan, it’s sometimes referred to as the Japanese oyster. There is some confusion regarding its taxonomy, with it also sometimes referred to as the Portuguese oyster, though it’s possible the two are separate species. They are large, jagged oysters, and occur in marine coastal waters.
How did they get here?
The oysters were imported into waters throughout Scandinavia and most of Northern Europe to replace dwindling stocks of native oysters at various points through the 20th century. Naturally, they eventually established wild populations as well, and are now abundant along Norway’s southern coast. Whilst they have taken over coastlines through much of Europe, their dislike of colder waters means that for now, their local populations are largely constrained to the south of Norway. But increases in temperature, which will occur at an accelerated rate in the Arctic and sub-Arctic, mean that the oyster could spread further north in the coming decades.
What do they do?
Much like the Red King Crab, they transform the local ecosystem into a homogenous mass. They can transform substrate from soft bottomed and muddy to filled with rocks and other oysters and mussels, also paving the way for other alien species, and lowering regional biodiversity by outcompeting and displacing local species. Interestingly though, presence of oysters can often improve water quality in the surrounding regions and heighten ecosystem productivity, though the position of the oyster in novel food webs is not particularly well understood. They also have negative effects for local human populations, making certain areas impossible to use for recreation, as they’re extremely sharp.
How do we stop them?
In other countries, attempts to eradicate wold populations by harvesting them have proved futile, and a 2005 study showed the oyster eradication would also cause substantial harm to the local ecosystem. Warming seas will mean the expansion of the oyster’s range, however this is likely to happen very slowly, so by focusing on the ranges edges it may be possible in the future to limit expansion.
For more information on the oyster, we recommend that you read the following articles:
Invasive Alien Species Fact Sheet – Crassostrea gigas by the Online Database of the North European and Baltic Network on Invasive Alien Species
Crassostrea gigas – Cultured Aquatic Species Information Program by the Fisheries and Aquaculture Department of the United Nations
Once again, let us talk about trees. Do not be fooled by their innocent appearance – that is exactly what they want! In reality, they can be just as problematic as any animal species. This week I takes a closer look at the Sitka spruce (Picea sitchensis).
Image Credit: Michelle Pemberton, The Children’s Museum of Indianapolis, CC BY-SA 3.0, Image Cropped
“… a red army of monster crustaceans – marshaled by Soviet-era leaders – is threatening to invade Western Europe …”
– James Owen, National Geographic, 2004
Ominous. That’s the thing, isn’t it. Some invasive species look harmless. You can’t be scared of a baby Canada Goose, can you? Or a nice purple garden flower. Such florescence. You can, however, be scared of a spiny, alien-looking 10 kilo mass of spines and pincers that has been shuffling its way into Norwegian waters over the last half-century.
What are they?
Paralithodes camtschaticus, the Red King Crab, is the most heavily fished crustacean in Russian seas. They fetch a high price at the market, and over 50 million USD was made in exports in Norway alone in 2016. A common trait amongst invasive species, they are a generalist predator, and will eat anything, from small invertebrates to large echinoderms and bivalves. They are among the largest arthropods living, with 8 legs, 2 pincers, a carapace of around 22cm, and an unholy mass of mandibles and spines to go with it. They are also quick movers, and can relocate based on available food quickly. Basically, if I were a sea urchin, were it not for the sea urchin’s general lack of the concept of fear or any other emotion, I’d be terrified.
How did they get here?
The crab is native to the northern Pacific Ocean, but like the Pink Salmon, they were deliberately stocked into the Murman coast by Russian scientists for commercial fishery. Since the 60s the crab has spread into Norwegian waters, and was well established in Northern Norway by the 90s. Soon after this the population skyrocketed, and the majority of fjords in Northern Norway are now occupied by the crab. Whilst the crabs prefer colder temperatures, increased temperature doesn’t seem to be a barrier for migration, and the fact that there are also reports of human introductions as far south as Bergen should be worrying.
What do they do?
Their role as a large predator of pretty much anything, combined with the fact that they migrate between different depths and are fast movers, mean that they can significantly change the physical structure of the ecosystem that they inhabit very quickly. Their removal of larger bivalves and echinoderms has lead to lower diversity and abundance in Norwegian fjords, particularly among species with low motility, and subsequent changes in the entire community composition of an ecosystem. They can also contribute to a loss in production and nutrient recycling, and subsequent drops in populations of local fish.
How do we stop them?
This is difficult, and marks the point in this series where we need to actually consider the term ‘invasive’. So far, I’ve considered invasive species as alien species which demonstrate a negative effect for the ecosystems they are novel to, or on the economy of a nation, with no pronounced positive effects in any other aspect. However in many international and national laws, invasive species are those which have a negative impact on human health or economy. And here lies the issue. Whilst the Red King Crab has an undeniably negative effect of local biodiversity, it has a undeniably positive effect on the Norwegian economy.
I’ll return to this topic next week, but for now let’s approach the issue as if we want to stop the incursion. The crabs seem to display high site loyalty, which means that they’re theoretically easy to prevent from spreading further down the Norwegian coast, given correct management.
The crabs prefer cold waters so let’s keep that climate change going and drive them out of Norway oh dear God my apologies that’s a terrible idea.
Reducing supply-and-demand lessens the crab’s economic value, so avoiding crab meat is a good step. Yet the Norwegian government’s tactics here are more likely to make a difference. Currently the practice is to maintain a certain capacity in some areas, whilst aiming for fishing to eradication in areas further south to prevent spreading. However there is little incentive for fishermen to eradicate a substantial part of their livelihood, so these regulations may need to be more strictly enforced, or the quota regulated areas restricted further.
For more information on the crab, we invite you to read the following articles.
Giant Crab ‘Red Army’ Invades Norway by James Owen for National Geographic News
Invasive Alien Species Fact Sheet –Paralithodes camtschaticus by the Online Database of the North European and Baltic Network on Invasive Alien Species
Current Status of the Red King Crab and Snow Crab Industries in Norway by Lorentzen et al.
Thermal behaviour and the prospect spread of an invasive benthic top predator by Christiansen et al.