Since April I’ve been staying on my boat on Hovedøya, just one of the little islands in the inner Oslo fjord. Large parts of the island are protected by the Cultural Heritage Act. This is were I live in the summer season. I mostly stay on the island unless I really need to leave (for example, to buy provisions), even though the city is very close. Almost every day I clear up the stoney beach close to the jetty, finding all kinds of plastic, glass, syringes and a lot of other rubbish washed up on the shore. Today I found something quite alien and alive.
I have observed the urban development of Oslo Harbour from my boat for the last six summers and have found that this development has contributed exponentially to the amount of rubbish I gather each morning. ∼ Many people crowd onto the recently constructed city beaches to enjoy the sun and sea. When this happens many castaways, such as ice cream wrappers, chicken bones, tampons, condoms and doggy poo bags, come floating over to the little stoney beach. The ferries that go to the small islands depart from a more accessible location than before, greatly increasing the number of persons that visit the islands. In the high season I dream that Hovedøya is sinking under the weight of all the visitors.
This morning the water level was very low, exposing less contemporary objects in the mud; thick broken glass (cloudy coloured, dark brown, green and black) that must have come from very old bottles, pieces of old pottery and large iron nails from traditional wooden boats. I also found a scattering of Pacific oysters (natives of Japanese seas) anchoring themselves to the rocks. Never before have I found a wild oyster on Hovedøya.
Recently there has been a rapid expansion of Pacific oyster (crassostrea gigas) populations on the Scandinavian coasts. The oysters have been referred to as ecosystem engineers; species that have the ability, directly or indirectly, to modify, create or destruct habitats.
Unlike the ‘native’ oysters of Norway, which are oval and rather flat in form, the shells have sharp edges and are shaped by the environment they inhabit. I found such oyster shells filling in the niches between rocks. In Apr 2016 I helped organise a seafood foraging course at Steilene, just a little further south from Oslo. The oysters we harvested were much larger than those on Hovedøya and more conformable in shape. I presume that the oysters on Hovedøya are young ones, first cementing themselves in the gaps between rocks before growing bigger. Given time, they may establish themselves as a large colony. Given the right conditions Pacific oysters can live up to about 30 years.
Much like the invasion of the Alaskan king crab some years back, the explosion of wild oysters along parts of the Norwegian coast are about to displace native species, and may also account for the very low count of mussels in Norway this year. The normally shy eider ducks that migrate to Hovedøya in the spring must be feeling this recession too. Each day, family groups pay frequent visits to my boat, diving under the water to feed on mussels living on the keel. From inside the boat the collective noise they make is phenomenal, sounding like a sea monster trying to find a way in. I try to supplement their diet with bread crumbs, but they just they throw their beaks up in distain. Not surprising really, as they feed on mussels, clams, scallops, sea urchins, starfish, and crabs. Mussels are their favourite food. Oysters are mine.
If I had been given the option of oysters or bread, I would opt for oysters – breakfast, lunch and dinner (preferably with a slice of lemon and a glass of champagne). Gobbling them up seems a good way to go to restore some balance in the local ecosystem. Others have been thinking about this too. I found an article in The New York Times; Chinese Offer to Eat Denmark’s Oyster Problem to Extinction (28.04.2017).
Briefly; soon after the Danish Embassy in Beijing released an online report about a ‘plague’ of Pacific oysters along parts of the Scandinavian coast, over 15.000 social media comments and recipes came flooding in.
Most of the advice offered by commenters boiled down to a simple solution: Send armies of Chinese tourists to scarf down the oysters. But that advice often came with a witty twist: “Free up visas and introduce oyster-eater visas, 10 years unlimited re-entry,” said one of the initial suggestions. “I’d bet that these oysters would be exterminated in about five years.”
“I solemnly swear to join the Danish Oyster-Resistance Volunteer Army,” said another. “I will dedicate my tongue and taste buds to Sino-Danish friendship until these oyster invaders are vanquished.”
To such comments, the Embassy replied;
“Thank you to the righteous advance team of oyster eaters,” …. “The beaches of Denmark await you.”
Like the king crab, Pacific oysters may become a lucrative export product, but whether this will have a positive effect on local ecosystems remains to be seen. A recent article, DNA analyses reveal secrets about the Pacific oyster (NIVA 28.06.2017) probes this issue. It is one of global climate change, larvae drifts, simulated ocean models and genetic analyses.