The Burbot, Lota lota, is a Northern Hemisphere freshwater fish that is physically distinct from other fish in its environment. It has an elongated body and is laterally compressed with its head appearing partially flattened (McPhail & Paragamian, 2000). In addition, the Burbot has a characteristic dorsal fin arrangement; it possesses two soft fins, one being short and positioned anteriorly on the fish and the other being much longer and spans almost until the caudal fin (McPhail & Paragamian, 2000). Moreover, the Burbot’s anal fin is similar in shape to the dorsal but is shorter in length. On the head of the Burbot, there is a small projection on each nostril and a single barbel evident underneath the center of the tip of the chin. While cycloid scales are present on Burbot, they appear very small and are not useful for determining the age of the specimen (McPhail & Paragamian, 2000). Therefore, it can be assumed that the near-microscopic scales and their counts do not lead to consistent identification of Burbot. Visually, the Burbot’s mouth is terminal in position and is medium-large in size when compared to the rest of its mottled body and can be seen to parallel the other species in its family (McPhail & Paragamian, 2000). With regards to the typical size and dimensions of Burbot, average lengths are 30-60cm and have weights of one to three kilograms, but they can also attain lengths up to one meter and weights up to eight kilograms (McPhail & Paragamian, 2000).

Systematics:  

The Burbot has a very peculiar taxonomical position in its family, primarily due to its environmental and geographic characteristics. Although a purely freshwater fish, Lota lota is a species under the marine-dominant cod family, Gadidae. (Chen, 1969). Because the geographic range of L. lota is so wide, its taxonomic classification has had much controversy, particularly in relation to the presence of any subspecies within Lota lota. Having only been exposed to approximately four glacial cycles, L. lota has only recently been re-established in the Europe region and this separation in time period might have provided insight into the extant assemblages (Van Houdt, De Cleyn, Perretti, & Volckaert, 2005). There has been contention to what degree  L. lota is subdivided, but it has been commonly agreed upon that at least three different subspecies are evident (McPhail & Paragamian, 2000). These include Lota lota lota being present in the European and western Siberian populations, Lota lota lacustris in the eastern North American range, and finally Lota lota leptura in the northwestern North American and Eastern Siberian regions (McPhail & Paragamian, 2000).

The Burbot is a species that is primarily found in cold freshwater and so it is widely distributed in the Holarctic regions of the world (Ryder & Pesendorfer, 1992). This suggests that its range encompasses much of northern Europe, Asia, and North America including Minnesota (Ryder & Pesendorfer, 1992). As such, benthic regions of deep-water lakes like Lake Superior would be ideal conditions for Burbot to live in, since they would be able to comfortably conform to their surroundings (Ryder & Pesendorfer, 1992). Such conditions include Burbot living below the thermocline during the summer and being found in water temperatures of around 10-14 degrees Celsius (Stepanian et al., 2010). These cold environments parallel those that the Burbot’s marine relatives typically inhabit throughout the northern oceanic waters (Stepanian et al., 2010). Within these deep regions of freshwater bodies, Burbot tend to dwell among benthic features ranging from tree roots, rocks, and dense vegetation, as all of these refugia serve as both a source of protection and food acquisition (McPhail & Paragamian, 2000).

Food: The Burbot can be appropriately described as a voracious predator and has been noted to be a potential competitor for food with other fish within its endemic environment. As such, it has been recorded by various studies that the diet of Burbot consists of over 80% fish (McPhail & Paragamian, 2000). Specifically in North America, the range of fish that they prey upon is quite large and includes a spectrum of species such as lampreys, whitefish, grayling, northern pike, suckers, sticklebacks, and other Burbots (McPhail & Paragamian, 2000). Depending on the season, the diet of Burbot with regards to specific species can likely be seen to shift with their respective availability in the present environment (McPhail & Paragamian, 2000). This versatility in diet is beneficial for Burbot as it means that they would have few natural predators besides larger fish in families such as Esocidae. Other Interesting Facts: The skin of the Burbot is reported to be very tough and because of its documented presence across Russia, it has been reported that its skin has been used as a glass substitute for windows in regions of Siberia (Minnesota Department of Natural Resources, 2019). Reproduction:  

Being a freshwater fish, the life history of the Burbot is directly tied to the presence of the lakes, rivers, and streams it inhabits. Within lakes, mature Burbots aged four to seven specifically spawn above shallow waters near shores in substrates that consist of silt-free sand, gavel, or cobbles (McPhail & Paragamian, 2000). Pertaining to Minnesota, spawning in the Great Lakes has actually been noted to occur in deeper waters (McPhail & Paragamian, 2000). Like their marine cod-cousins, Burbot reproduce by means of broadcast spawning into the water column which would entail positioning the eggs above the chosen substrate where they will eventually settle depending on the current (McPhail & Paragamian, 2000). However, the way this occurs is that a spawning “ball” is formed where many male Burbot surround one or two females and the eggs and sperm are simultaneously released (McPhail & Paragamian, 2000). Also analogous to other cods, the fecundity of Burbot is very high in that the average spawn batch ranges from 6,300 to 3,477,699 eggs (each with about a 1mm diameter) and this is also dependent on the corresponding geographic area and body of water (McPhail & Paragamian, 2000). With such a high number of eggs being fertilized at once, there would be virtually no parental care. This is evident by the newly hatched larvae exhibiting a passively pelagic behavior (McPhail & Paragamian, 2000).

In North America, the Burbot has yet to be considered a species that is at the forefront for immediate conservation due to its difficulty for studying. This stems from its deep-water life and reproduction under frozen waters. However, riverine Burbot populations have been declining due to anthropogenic pollution and habitat change while lacustrine populations have been negatively influenced by the introduction of invasive species (Stapanian et al., 2010). There is no federal status designation for the Burbot and there are few commercial fisheries geared towards this species, so this subsequently leaves the Burbot with little in terms of population management plans (Stapanian et al., 2010).

McPhail, J. D., and Paragamian, V. L. 2000. Burbot biology and life history. Burbot: biology, ecology, and management. American Fisheries Society, Fisheries Management Section, Publication (1): 11-23.

Van Houdt, J. K. J., De Cleyn, L., Perretti, A., & Volckaert, F. A. M. (2005). A mitogenic view on the evolutionary history of the Holarctic freshwater gadoid, burbot (Lota lota). Molecular Ecology, 14(8): 2445-2457.

Chen, L. C. (1969). The biology and taxonomy of the burbot, Lota lota leptura, in interior Alaska. University of Alaska. Institute of Arctic Biology, (11): 1-53.

Ryder, R. A., & Pesendorfer, J. (1992). Food, growth, habitat, and community interactions of young-of-the-year burbot, Lota lota L., in a Precambrian Shield lake. Hydrobiologia, 243(1): 211-227.

Stapanian, M. A., Paragamian, V. L., Madenjian, C. P., Jackson, J. R., Lappalainen, J., Evenson, M. J., & Neufeld, M. D. (2010). Worldwide status of burbot and conservation measures. Fish and fisheries, 11(1): 34-56.

Minnesota Department of Natural Resources. (2019). Species Profile – Burbot. Retrieved from www.dnr.state.mn.us/minnaqua/speciesprofile/burbot.html.