Migrant Oysters on the West Coast of Sweden
- biordinary
- Aug 29, 2024
- 8 min read
Ordinary Place
Most of the West Coast of Sweden is in BIOrdinary terminology an ordinary place. Human interests and activities fall mainly into three major domains in this region: residence, recreational activities, and maritime economy including shipping industry, transport, and on a somewhat smaller scale seafood extraction and production. However, as in the rest of Sweden, there are several nature reserves, one national park, Kosterhavet, as well as EU initiated Natura 2000 regions, areas that are protected to different levels for the sake of both recreation and preserving biodiversity (Naturvårdsverket 2024, Länsstyrelsen 2024). The legislation for the ordinary places does not have biological diversity as a goal, although internationally compared, Sweden still has relatively strong environmental laws and regulations.
Because of different human interests in the region, conflicts arise between different groups of actors as to how to best use coastal areas and marine resources. Two recent examples were the failed plans for building a transatlantic container harbour in Lysekil (NyTeknik 2018) and the conflict around recreational small boats that have caused both marine pollution with their paints (e.g. Lagerström 2019) and a dramatic deterioration of eel grass beds resulting in biodiversity decline (e.g. Eriander et al. 2017). The appearance of Pacific oysters, Magallana gigas, in larger numbers and in ordinary places where they became increasingly visible, was one of the phenomena that stirred feelings some years ago, and caused considerable attention in media, with consequences for local governance and national legislation.
Biodiversity Dilemma
Pacific oysters were first observed on the West Coast of Sweden in Autumn 2006, and were soon to be perceived as an “invasive alien species” (IAS) that threatens endemic species and ecosystems, jeopardizes human recreational activities, and should consequently be exterminated. Parallel to this, however, the newcomer oysters were also met by curiosity, not the least by marine biologists and some local residents. As a consequence of this curiosity, today there are several research and entrepreneurial projects that explore Pacific oysters’ potential for ecosystem services (e.g. DynamO project).
Marine research has so far established that the Pacific oysters are “ecosystem engineers”, that is, they change the ecosystem for their own benefit. However, this changes the ecosystem also for other species. By building clusters and reefs, Pacific oysters change the soft sea substrate of sandy bays, into hard sea substrate of the oyster reefs, and thus also the existing ecosystem. Some species do not thrive in the new ecosystem with the hard substrate, but it seems that the harder substrate provides for a larger biodiversity than the soft one: a larger number of species seem to be able to find shelter, oxygen, nutrients, virus protection, and other benefits, where the Pacific oysters have established themselves.
Thus, one biodiversity dilemma is the contradictory definition of Pacific oysters as an “invasive alien species” that jeopardizes the biological diversity (Roy et al. 2023), while in practice they increase biodiversity in places where they have settled.
The other biodiversity dilemma with Pacific oysters is their contradictory role and relationship with humans. On the one hand, human recreational activities are jeopardized in some places because Pacific oysters build reefs in relatively shallow waters where people bathe or use small-boat passages. The sea passages can get completely blocked, while bathers easily cut their feet on hard and sharp shells. On the other hand, the decline of European flat oyster, Ostrea edulis, and Blue mussel, Mytilus edulis, has left some niches relatively empty, which are now becoming increasingly occupied by Pacific oysters. While European flat oyster has steadily been on decline during the last century, mostly due to overfishing, Blue mussels have become scarcer only during the last decade or two. Both species are probably declining also because of the rise of the sea temperatures due to the climate changes. Pacific oysters, on the other hand, seem more adaptive and robust than their flat relatives and Blue mussels. Thus, they have a potential of filling, not only the “ecological niche” left vacant by European flat oysters and Blue mussels, but also the empty “economic niche” as seafood. Besides that, they could also provide other products (for example, calcium in the shells could be used as nourishment in chicken farming, or for regulating the acidity of inland lakes). Moreover, they could potentially also fill the “cultural niche” left increasingly empty by the declining Blue mussel, which was used as local sea food, but also as a bait when fishing crabs with children – a summer activity commonly perceived as an essential part of a happy Swedish childhood.
Mobile Species
The mobility of Pacific oysters’ that brought them to Swedish shores is both anthropogenic and biogenic. Before the 20th century, the Pacific oysters were found mostly in the Pacific Ocean as their name reveals. But in early 20th century, the import started, first to the US, and later in the 1960s also to Europe. As they were more robust to diseases, grew much faster, and became larger, they were seen as superior to older local oyster species. In Europe, they were imported to boost the aquaculture after the earlier oyster species have been decimated by diseases, probably due to the warmer sea temperatures. Even Sweden and Norway tried to start Pacific oyster aquaculture in the 1970s but did not succeed, probably because of the too low seawater temperatures at that time. Within the coming decades, however, the sea temperatures have been steadily rising, making even Scandinavian coasts of North Sea and Skagerrak suitable for the species. Genetic mapping has shown that the majority of contemporary Pacific oysters in Sweden have come in 21st century, “hitchhiking” on sea currents from more southern parts of Europe, in particular Denmark (Faust et al. 2017). It is possible that some have survived the aquaculture attempts in the 1970s and re-emerged in ordinary and visible places after 2006, but that needs yet to be proven. Due to the general rise in temperature resulting in exceptionally dry summer of 2018, which in its turn heightened the salinity in the Baltic sea, in 2019 Pacific oysters have been noted for the first time also there. However, since the salinity dropped in the coming years, they have yet not managed to establish themselves in the Baltic sea. However, because of their relatively good genetic plasticity, it is possible that the Pacific oysters will be able to gradually adapt to lower salinity levels, and thus also establish themselves in the Baltic sea.
Actors and Actants
Today, a range of human actors relate to the newcomer oyster: marine biologists and ecologist; local fishermen and landowners; permanent summer residents and tourists; seafood entrepreneurs; food and tourist industry; municipal, regional and national governance and policymakers.
Apart from human actors, also a range of other species as well as abiotic actors (or actants) relate daily and closely in different multispecies communities and assemblages that can be found in ordinary places where Pacific oysters have settled. In my research, I look at all the related species in these settlements, from different algae and fishes to crustaceans and other molluscs, but also different microorganisms.
The abiotic actants that shape the Pacific oyster communities and assemblages are sea temperatures and salinity, the former necessary for survival and reproduction, while the latter putting stop to their migration into less salty waters. Further important actants are sea currents that enable migration, and wave activity that prevents Pacific oysters from settling on exposed cliffs and shores. It seems that Pacific oysters prefer shallow waters, although they can be found also on depths up to 10 m, so water pressure and light might also have some effect. Last but not the least relevant, are all the toxins that Pacific oysters accumulate in their flesh through intense filtration of sea water, and that have large impact on how humans relate to them.
History
Archaeological remains show that oysters were used as seafood already during the stone age, in several places, including Scandinavia. Ever since, they have been used in different cultures and during different periods as food, but also as decoration and perhaps also money. Pacific oysters in particular, have been used mostly as food, as were their predecessors in Swedish waters, European flat oysters. From being a poor man’s diet, at the end of 17th century oysters turned into food exclusive to the Swedish Royal Court. Despite this restriction, the number of oysters kept declining, most probably due to cold winters and overfishing. The total ban for citizenry was introduced in 19th century, as well as prohibition to pick too small specimens. However, this ban did not have much effect on local practices, and the decline of the European flat oyster continued. In 20th century, oysters in Sweden became property of landowners by law, and when Pacific oysters appeared on the shores of Sweden, they too became property of landowners, by default. Thus, Pacific oysters are not covered by Swedish Allemansrätt, a right of public access to privately owned lands, with some limitations, to for example pick berries in the forest, or Blue mussels in the sea. Consequently, it is not allowed to pick “invasive” Pacific oysters without landowner’s permission. However, in practice, as with the Royal decree of 19th century, people pick oysters quite unconcerned by the landowners’ rights, both European flat oysters if they can find them, and the Pacific oysters which more abundant and easier to access.
Future
As the time goes, humans have changed not only their attitudes and affects, but also their practices of use of Pacific oysters: from the initial interest of marine biologists and genocidal hate of summer residents, to local curiosity and changing of local habits in relation to the changing marine world. Also economy and laws are changing. At the moment, the Allemansrätt is under consideration to be extended to include also Pacific oysters, which would allow the public to pick them freely. Several experimental projects for making Pacific oysters an important seafood nutrient, seem to lead to a future for Pacific oysters similar to other unpleasant but useful species: the Pacific oysters will probably be farmed on designated aquafarms and be exploited by humans for various other “Ecosystem Services”, while tourists and recreational industry will cleanse them from the beaches where they are a nuisance to bathers, at the same time exploring the gastronomic possibilities, luxury as well as everyday ones (as, for example, in oyster burgers, which are part of a current street food project). Projects to clean the polluted sea-waters with help of oyster filtration, as is attempted in New Your harbour (Wakefield 2020), have not yet been initiated in Sweden. One reason might be that Swedish waters are still less polluted. Outside of human reach, Pacific oysters will most probably continue to thrive in Swedish and Norwegian, as well as other European, sea waters.
Marine biologists and ecologists are continuously learning more and more about the Pacific oysters in the warming world of climate change. In not only human world, other species are accommodating to the ecosystem changes caused by Pacific oysters’ settlements, and new relationships are bound to continue evolving, both those of mutual benefit, more neutral ones, as well as the predatory ones.
The aim of this project is to follow multispecies and abiotic relationships in Pacific oyster communities, in order to continuously deepen the knowledge of their complexity and variation. More generally, by developing more-than-human ethnographic methods to better understand the case of Pacific oysters on the West coast of Sweden, the aim is also to explore the processes through which humans and other species get to know each other in complex and everchanging ecological systems of the warming world.
References:
Eriander, Louise et al. (2017) “The effects of small-scale coastal development on the eelgrass (Zostera marina L.) distribution along the Swedish west coast – Ecological impact and legal challenges” Ocean & Coastal Management 148:182-194.
Lagerström, Maria (2019) Occurrence and environmental risk assessment of antifouling paint biocides from leisure boats. Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi. PhD Thesis.
Länsstyrelsen (2024) https://www.lansstyrelsen.se/vastra-gotaland/natur-och-landsbygd/skyddad-natur.html (Retrieved 2024-02-16)
Naturvårdsverket (2024) https://www.naturvardsverket.se/en/topics/protected-areas/different-types-of-nature-conservation/ (Retrieved 2024-02-16)
NyTeknik (2018): ”Planer på omtvistad kinesisk storhamn i Lysekil avblåsta,” https://www.nyteknik.se/nyheter/planer-pa-omtvistad-kinesisk-storhamn-i-lysekil-avblasta/516095 (Published 2018-01-31, retrieved 2024-03-22)
Roy, Helen E. et al. (2023) Summary for policymakers of the thematic assessment of invasive alien species and their control of the Intergovernmental Platform on Biodiversity and Ecosystem Services. Advanced Unedited Version, 4 September 2023.
Wakefield, Stephanie (2020) Making nature into infrastructure: The construction of oysters as a risk management solution in New York City. Environment and Planning E: Nature and Space, 3(3), 761-785.