Tag Archives: sturgeon

From sturgeons to round gobies

A while ago, I commented on the capture of a Russian sturgeon Acipenser gueldenstaedti, in southern Sweden. The fish now has a home in an aquarium at Universeum, where it moved in 5 May. Universeum is a Science center in Göteborg, located on the Swedish west coast. They have a web cam of their shark tank. I rather want to see the sturgeon!

Meanwhile it appears that German fishery biologists have indeed released plenty of Atlantic Sturgeon, Acipenser oxyrinchus, imported and reared from North American stock. The idea is to re-introduce an extirpated species. Without eliminating any of the adverse factors that killed the sturgeon and threatens all other life in the Baltic: fishery and pollution is just the first name. Will the introduced sturgeon become a further complication in a disturbed ecosystem or will they peacefully die away? Stay tuned.

German newspapers now report on catches (Berliner Morgenpost, 14 May 2009), and a tagged sturgeon (Acipenser oxyrinchus) was caught off Bornholm, a Danish island in the southern Baltic, on 6 May, the identification supported by newspaper photograph.

These sturgeons are apparently from a small number of large meter long sturgeons initially from Canada in 2005 but reared in Germany and recently released into the Baltic. Thousands of baby sturgeon have also been released this Spring according to the article in Berliner Morgenpost. 50 small tagged sturgeons were released in the Elbe in April. All the larger A. oxyrinchus released are tagged, and should be released again if caught — at least if you are a sturgeon fan. If the fish lacks the tag and has a very short snout, it is more likely a totally alien species; it is up to you what to do if you catch one. The expectation is that these fishes shall feed upon the rich benthic fauna in the Baltic and in ten years or so migrate up the Odra River on the border between Poland and Germany, and breed there, so re-establishing the sturgeon in the Baltic. The German Society for Saving the Sturgeon is one active organisation in this work with updated information on Sturgeon releases.

Whatever one may think of these experiments, fishing in the Baltic, always report your sturgeon, irrespective of species, to the nearest museum or other competent authority. Dead or alive there will be use for the information.

Another alien fish species is also coming up here. Last year, in July, a sport fisherman in Karlskrona, on the Baltic coast of southern Sweden, caught a strange fish which he kept in his freezer for a while. In November it was reported to the right scientist, and made some headlines. It was the first Swedish representative of the round goby, Neogobius melanostomus, a Black Sea species which has made itself at home in select locations in the Polish section of the Baltic since about 1990. Just a few days ago, the second specimen was reported, also this time near Karlskrona, which has both an important harbour and archipelago. It will be interesting to follow also the spread of this alien, which unfortunately will not go away as easily as the sturgeons may.

Neogobius melanostomus from Karlskrona, May 2009, NRM 51437.
Photo Bodil Kajrup, Swedish Museum of Natural History, CC-BY-NC.

Sturgeon fever


A sturgeon (Acipenser oxyrinchus) once owned by King Adolf Fredrik, studied by Linnaeus,
now housed in the Swedish Museum of Natural History collections.Photo A. Silfvergrip. Data . Image CC-BY.

Once upon a time there was in the Baltic Sea a fish known as the sturgeon. Its existence in Swedish waters were known to Linnaeus and Artedi, and Linnaeus named it Acipenser sturio in 1758, based on two small specimens in alcohol, and a skin, plus literature records. These two alcohol specimens are still in the collection of the Swedish Museum of Natural History. One comes from Amsterdam apothecary Albertus Seba, bought by King Adolf Fredrik probably 1752, the origin of the other one is more obscure.

From 1758 till recently the sturgeon was studied, fished, eaten and extinguished from European waters, save for a declining population in the French river Garonne, which defies rapid extinction despite cadmium poisoning and sexually asynchronous breeding (males and females do not breed at the same time …). Then a German-US team in 2002 (Arne Ludwig et al.) could show that the northern European and Baltic Sturgeon is genetically the same as the North American Atlantic sturgeon Acipenser oxyrinchus Mitchill, 1815, and not at all the same as the sturgeon in France, the Mediterranean, and the Black Sea.

Ooops … And this had already been demonstrated by morphological studies, that somehow did not draw the right conclusions.

Whereas there are still technical issues over which name goes to which species, the preliminary conclusion is that in the Garonne swims Acipenser sturio, and in the North Sea and the Baltic Acipenser oxyrhinchus was as much at home as in the United States.

The Baltic sturgeon is extinct in Europe. The last specimen identified as A. sturio in the Baltic died in 1996, and was an A. oxyrinchus.

Nevertheless, Swedish media the last two days have enthusiastically declared the return of the sturgeon! Based on a fish taken outside the island of Öland in the Baltic Sea, 10 of April by fisherman Ulf Åkerlund.

From the local newspaper scoop we learn that the fisherman is excited (as he should be; this is an uncommon fish whatever it is), and the Fisheries Board expert is more interested in tasting the roe than getting it properly identified.

From the published image, you can see the mutilated pectoral fin indicating a pond cultured fish. And what more, it looks not like a sturgeon but resembles more the Russian sturgeon Acipenser gueldenstaedti, and could also represent Siberian sturgeon Acipenser baeri. Although there are efforts to reintroduce Acipenser oxyrhinchus into the Baltic, I am not informed of any releases having taking place yet. If and when it happens it will be a great waste of money on a lost case.

The “sturgeons” we now have in the Baltic are escapes from cultures of Siberian and Russian sturgeon and hybrids between different species. They look like sturgeon because all 20+ species of sturgeons look about the same. In May 2000 a small “sturgeon” was caught in Kalmarsund strait and given to the Swedish Museum of Natural History (NRM). The specimen was sequenced and blasted as Acipenser stellatus, which it is not, and morphologically identified as A. baeri.

Other more or less recent Swedish “sturgeons” include a Siberian sturgeon from the Stockholm Archipelago in 1969, a Russian sturgeon from Lysekil in 1970, and one “sturgeon” from Skåne in 2007 that, like one from Kummelbank in 1991, has not been identified yet. Browse sturgeon data in the NRM fish collection.

Will we know which species was caught this time? It would be a good thing to build up knowledge as early as possible about potential “sturgeon” invasions in the near future, and we could learn more how to identify the fishes, and using molecular and morphological markers track the movements of these aliens in our waters. Let’s see what tomorrow has in store.