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.


Fish from nowhere

Yesterday I mentioned briefly the leopard danio, a small golden fish full of dark spots, apparently a color mutation in the zebrafish Danio rerio, but described in 1963 as a species on its own with the name Brachydanio frankei. The leopard danio is a popular aquarium fish in its own right, which keeps its colors but does not differ in behaviour or size from the zebrafish, and hybridises freely with zebrafish. When it first appeared in the aquarium trade, its origin in the wild was unknown. That should have called for some caution … On the other hand, who could believe other than that the differences in colour pattern was a strong indicator of species distinctness?

Spotted danios are known from the wild, however. There is Danio kyathit from northern Myanmar, in which the spots are more or less irregularly arranged in rows, and many morphological characters distinguish it from other species of Danio. Described by Fang in 1998, based on four specimens she collected herself, she also included two specimens collected in the 1920s that were not spotted but striped. There was simply no way of distinguishing the striped and spotted kyathit other than by colour pattern, and because the rows of spots are merely broken up horizontal stripes, there was room for considering intraspecific variation. How different conclusions can be once you know a little more about the group you are working with!

Here is an image of Danio kyathit, photographed by Fang Fang.

The other spotted danio has no scientific name yet. It is a small fish, similar to Danio rerio but with large spots on the side. It is already available in the aquarium trade where it is called Danio sp. Burma. Will anyone dare to describe it? Is there a striped counterpart already available among the many supposed synonyms of Danio rerio??

A real sunshine story is the that of the “Odessa barb”, one of the major aquarium fish species, and belonging to the large family of cyprinid fishes. Males are marked by a stunning, glowing, deep, exquisitely brilliant red band along the side, and contrasting black spots in the dorsal, anal, and pelvic fins. Females are less colourful. It is or relatively small size, less than 5 cm, and easy to reproduce in aquarium.

The early aquarium history of the “Odessa barb” is not well documented. In 1973, Russian aquarist Dazkewitsch wrote that it originated from a market, not stated where, and arrived in Odessa, Ukraine, in 1971, soon being cultivated in Moscow. So it was named “Odessa barb” although quite evidently a South Asian species. It was a confusing time, a time for much speculation among American and European aquarists, and no information from Ukraine. And how come a small aquarium fish, soon of world fame could first be found in Ukraine, at the time part of the Soviet Union and with no aquarium fish import? Maybe it was also a “form” of some kind, like the leopard danio? Strangely, nobody got the idea this time to describe the new fish as a new species!

So, things remained for 30 years till Frank Schäfer in 2001, working for the German wholesale aquarium fish importer Glaser reported having found the “Odessa barb” in an importation from Myanmar.

Wow! And I and my colleague Ralf Britz (yes, that’s him with the vampire fish), missed it totally on our collecting trip in Myanmar just a little before, in 1998, crossing the country from Yangon in the south north to the foothills of the Himalayas in Putao.

Well, there was still no precise locality. And Ralf then found the fish in 2003, near Mandalay. So, it exists in nature, we know where, and last year we got it described. We named it Puntius padamya. Padamya is the Burmese word for ruby. The ruby barb of aquarists, however, is Puntius nigrofasciatus from Sri Lanka. The description is available online as an Open Access resource from the Electronic Journal of Ichthyology.

The “Odessa barb” freshly collected in the wild, a bit pale in the photo tank. Photograph by Ritva Roesler, from Kullander & Britz (2008: Electronic Journal of Ichthyology, 4: 56-66):

And the stately preserved holotype of Puntius padamya:

The lessons, if any, are: Don’t name fish known only from the aquarium trade. Be patient. And, give nice names to nice fish.

Zebrafish in spirits

Zebrafish (Danio rerio) are probably the most important fish for understanding humans. They are small fish, 2-3 cm long and native to India, Bangladesh, and Pakistan. Most conspicuous about them is the contrasted coloration with alternating blue and white horizontal stripes, even extending onto the caudal fin. That means they are horizontal where zebras are vertical. Otherwise there are no similarities 🙂

Zebrafish occur in many places in India, in the north in the Indus, Ganga, and Brahmaputra as well as in Kerala in the south, but appear uniform in color pattern and other morphology. They live in schools in different habitats, and are often collected in large numbers. As aquarium fish they are hardy, easy to breed, and prolific.

The distinctive colour pattern, which can be genetically altered, ease of keeping, and the fast generation time contribute to zebrafish status as a so-called model organism, which developmental biologists use to study the development and inheritance of various structures. Recently also, zebrafish researchers have been helped by improved understanding of the systematics of the group of fishes to which zebrafish belong, so that structures can be studied comparatively in closely related species.

Here is a dead zebrafish in alcohol from Assam, India. Not very colourful, but useful for taxonomic studies.

I just spent two days writing a description of a new species that I and my student Te Yu Liao collected last year (about this time) in Myanmar. There are many species of fishes closely related to the zebrafish. Thirteen species have been named in the genus Danio, and at least ten more species remain to be described. Most fascinating among the zebrafish relatives, is the leopard danio, which turned up in aquarium circles in Czechoslovakia in the 1960s and was described as a new species with the name Brachydanio frankei. This form, with small dark spots all over the body and fins, has never been found in the wild. It is probably a mutant of zebrafish, differing only in the irregular colour pattern. The genus, however, includes species that are spotted for real.

I will come back to fish species that only exist in the aquarium trade later. Let us round off the day with some zebrafish entertainment.

If you need just an overview of zebrafish, with the basic data, try Fishbase.

Wikipedia insists on being very technical about zebrafish

These developing zebrafish embryos are just irresistible:

The Wolfgang Driever Lab at the University of Freiburg has still images so you can track all the details at different stages. Click the image (from their website) to enter the zebrafish anatomy:

And then there is an enthusiasts’s website with images of various zebrafish-like species, Pete Cottle’s Danios and Devarios.

In the beginning …

This is a fast start blog to introduce myself (only a glimpse) and what possible kind of writings can be expected here.

As an ichthyologist, I will write mainly about fish. I manage two e-mail lists, my twitter, and blogs for two projects. Let’s see if there is more to say.

As a biodiversity informatician, I will try to connect fish with computers. I already post biodiversity informatics news on a Swedish language blog. Let’s see if there is more to say.

Naturally, I must first introduce you to those wonderful resources.

cichlid-l is the discussion list for professionals and others interested in cichlids. Cichlids are freshwater fishes found in Africa, South and Central America, Madagascar and parts of Asia. It is the second or third most speciose family of fishes (and vertebrates). This list is fairly old, started in January 1995.

eurofish-l is the discussion list for all other ichthyologists, but with an intended focus on Europe and particularly the activities of the European Ichthyological Society.

I will be back about the access to these lists, since they currently seem to have been locked up behind the firewall.

The FishBase Blog is the news blog in FishBase. FishBase contains information about all the world’s fishes, available for free on the web, e.g., on the Swedish FishBase server.

The Swedish Fishbase team also maintains its own news blog, in the Swedish language.

And finally, GBIF-Sweden serves news form the biodiversity informatics world in the form of a blog.

Ah, twitter, somewhat neglected: http://twitter.com/svenok