Winter burbot spawning

Burbot(Lota lota) is a true mallard among fish, as it is the only one in our fauna that spawns in the fullness of winter, more precisely from December to February, sometimes March. He often leaves it under the ice when the waters are as cold as possible. Hence, its protection period is from December 1 to the end of February.

Burbot – the road to adulthood

Burbot become sexually mature between the ages of four and seven. The spawners then undertake short migrations to their destinations in the open waters of rivers and lakes. Lots of males then gather around one or two females, forming what is known as “the female’s”. spawn balls. Writhing in the pelagial, they release sperm and egg cells. The female, depending on her size, lays from 63,000. To nearly 3.5 million. eggs. Depending on the ambient temperature, incubation lasts from 30 to almost 130 days, with an optimum at 1-7°C. The eggs drift in the water’s depths before they settle in the cracks of the bottom. Its grains are spherical, with a diameter of approx. 1 mm, with a fat drop visible inside.

Freshly hatched fry remain in the pelagial, drifting passively in the open water. In the first year of life, the larvae grow rapidly, reaching some 11-12 cm in late winter. The two-year-old burbot is growing another 10 cm. Burbot juveniles are active at night, catching insect larvae, annelids and crustaceans. During the day he hides under rocks. Burbot switch to a completely demersal (benthic) lifestyle at nearly 5 years of age. Adults can measure 0.3-1.2 meters, and weigh from 1 to 11.5 kg.

One of a kind?

This type of reproductive biology is popular among marine species, while in rivers and lakes it remains a kind of peculiarity. Because also burbot is the only freshwater representative of the entire, how rich in species, order of codfish Gadiformes! These codfish, whose catch accounts for more than_{1/4 of} the yield of all marine fishermen. Pelagophilic reproduction is a physiological and ecological inheritance from oceanic ancestors (something like veliger-type larvae in freshwater rockfish among bivalves).

A number of fundamental similarities between burbot and codfish have been known to mankind for centuries. Anglo-Saxons sometimes called it “freshwater cod,” “freshwater ling” or “brosma (tusk).” Ichthyologists have long included Lota lota in the cod family Gadidae. Nowadays, a separate family of burbotidae Lotidae is increasingly distinguished, however, grouping mainly oceanic forms typical of saltwater, such as Gaidropsarus and Enchelyopus motes, Ciliata onos and the previously mentioned Molva mol va and Brosme brosme.

To this day, the prevailing view is that the burbot is unique, including in strictly taxonomic and phylogenetic terms (as the only representative of a monotypic genus). The Russians and Chinese have for decades considered “their” burbot from the Far East as a separate breed, or perhaps species. More recent genetic analyses have also prompted the distinction as a separate species of a population from the east coast of North America: the spotted burbot a.k.a. North American Lota maculosa.

It is noteworthy that fish from the western, Pacific coasts, however, would belong to the same species as the European and Asian ones. A similar distribution pattern (same species in Europe, Siberia and along the Pacific coasts of North America, but different on the Atlantic coasts) characterizes some plants, e.g.: northern chamedaphne.

From a fishy weed to a charismatic species

People’s attitudes toward burbot have changed over the centuries. Its distinctive appearance, with a severely elongated body and only one “hair” on its chin, made it seen as a hybrid of catfish and eel or cod/molva/brosma with catfish. By the mid-20th century. was regarded as a noxious fish weed in Europe. It was supposed to notoriously gobble up the eggs and fry of the more valuable fish, especially salmonids, wigeon and grayling, both native and imported from across the Great Water to make the originally fishless lakes of the Alps and Carpathians more productive. Before cormorants took over Europe’s midlands, the burbot was blamed for the loss of other valuable fish, frogs or crayfish.

As a fish that requires well-oxygenated, cold and transparent waters, burbot have proven to be very sensitive to wastewater delivery and river regulation. In the 20th century. has become extinct in the UK and Belgium, is rapidly receding in France, and is becoming increasingly rare in Germany and Poland. In England, the Lota lota has become a kind of symbol of increasing water pollution and disappearing fish, a charismatic species like the Baltic sturgeon in Poland. Last year’s golden algae bloom in the Oder River took the lives of many burbot [1, 2], so the restoration of Oder’s shoals was among the demands of scientists, anglers and NGOs.

However, there are areas where conservationists and anglers continue to war against “freshwater ling”. These include the Colorado River basin (especially the Green River and Flaming Gorge reservoir) in the US. Lota lota, as an alien species to the streams there, is blamed for the destruction of native salmonid populations: rainbow trout, Clark salmon, kidney and lake pileated.

About the burbot that is not a burbot. King of the tables, but no longer a burbot

Many people may ask: if this species is disappearing in our country, how come there are so many affordable burbot in stores and restaurants? From the seas of the other hemisphere! Sometimes you may hear or read that “king burbot,” “sea burbot” and the common, adjectiveless “burbot” are one and the same fish. The facts are different! The vast majority of “burbot” offered in Poland are members of a completely different genus, family and order, caught in the south of the globe, in the ocean surrounding the Antipodes, Chile, southern Brazil and South Africa. Namely, these are Genypterus kinglipedes of the slipper family Ophidiidae, order Slipper Ophidiiformes. Predominant among them are New Zealand kinglets (“ocean/sea burbot”) Genypterus blacodes and Cape (cape, “king burbot”) G. capensis.

The relatively closest relative to the true Lota lota would be the red forkbeard (“red burbot”) Urophycis chuss, which is rarely eaten in Europe, as an undoubted member of the order codfish, or even codfish, well maybe the forkbeard Phycidae.

Typical problems of an unusual fish

Although burbot differ so strongly from typical river and lake fish, they share a number of problems with them. It was among the species hardest hit during last year’s environmental disaster in the Oder River. He is losing a number of positions in Eurasia, while at the same time “rampaging” in his new American homeland, reducing the population of “natives.” The situation is similar for the sea lamprey Petromyzon marinus – critically endangered and functionally extinct in Europe, despite species and habitat protection, and increasingly common (despite extermination) in the US.

It has disappeared from store shelves, although we haven’t noticed it, since we purchase completely different fish under the name “burbot”. Very similar stories can be told about:

• total of European Silurus glanis, replaced at markets and bars by the African tawada Clarias glariepinus or, worse, by the invasive batrachus Clarias batrachus (a fish on the list of the world’s 100 most dangerous invasive species), which is dangerous to native wildlife and other aquacultures;

• domestic brook trout S. trutta morpha fario, lake trout S. trutta m. lacustris, and sea trout S. trutta m. trutta, displaced by rainbow trout (“salmon trout” Oncorhynchus mykiss);

• sturgeon caviar, which had to give way to dyed tasza eggs or various “inventions” made of algae and preservatives.

Work on the domestication of burbot has been going on for at least a dozen years in China. As a lover of cold, well-oxygenated waters and a real glutton, it is to be bred analogously to salmonids. For the time being, however – despite advances in the field of domestication of other predatory fish, such as pike-perch – we don’t hear about true “freshwater lingcod” from Middle Kingdom fish farms. Lota lota also seems to be a promising model organism for research on fish resilience to sublethal, extremely low or, conversely, high temperatures. So let’s protect the habitats, so that our “freshwater cods” are not preserved only in the pages of “Ferdydurke”!

Sources used:

[1] Szlauer-Łukaszewska A., Ławicki Ł., Engel J., Drewniak E., Ciężak K. & Marchowski D. (2023).Quantifying a mass mortality event in freshwater wildlife within the Lower Odra River: Insights from a large European river. Science Of The Total Environment, 167898.

[2] IOŚ-PIB (ed.) (2023). The report concluding the work of the team on the issue. the situation in the Oder. IOŚ-PIB, Warsaw.