Coregonus lavaretus (Linnaeus, 1758)

Whitefish Coregonus lavaretus (Linnaeus, 1758) View in CoL

The whitefish is one of the most phenotypically variable freshwater fishes, in Norway and globally. This has led to large controversy regarding number and naming of species (Kottelat and Freyhof 2007). For example, in Sweden different authors have suggested the presence of many different species (see summary by Svärdson 1998). Gunnar Svärdson published during several decades numerous papers in a series he called “the coregonid problem”. And clearly the taxonomy and systematics is still a mess. Today, the SLU Swedish Species Information Center recognizes one species of whitefish, Coregonus maraena (Bloch, 1779) , with four taxa that are classified as morphotypes. In Norway, the Norwegian Biodiversity Information Centre recognized only one species, C. lavaretus . Also, in Finland the whitefish is classified as C. lavaretus by the Finnish Biodiversity Info Facility. Clearly, this is a situation that should be sorted out – as the whitefish clearly has a continuous distribution in Scandinavia.

One reason for the taxonomic confusion is the large phenotypic variability and also flexibility in use of spawning and feeding habitat. In Norway this has led to the presence of numerous reproductively isolated sympatric populations in many lakes. Many studies have focused on trying to describe this variability, using both classic ecological and population genetic methods (Østbye et al. 2005, Østbye et al. 2006, Siwertsson et al. 2013, Bitz-Thorsen et al. 2020). Most of these studies are from North-Norway or from the lake Femunden in mid-Norway. Clearly, there is still a need for more studies, from different geographic regions, in order to understand the origin and drivers of the genetic and phenotypic variation in sympatric whitefish populations. More extensive genomic tools are probably needed, such as full-genome sequencing using next-generation sequencing tools. An example of this is the detailed studies of a whitefish radiation in alpine European lakes (Vonlanthen et al. 2012, Frei et al. 2022). However, also here it can be discussed if the taxa studied are species, or populations of the same species.

One interesting topic that has been studied recently is on how various whitefish morphs/phenotypes are differentially impacted by the invasion of other species. In particular the effect of the invasion of vendace C. albula to Pasvik has led to the dramatic reduction in the abundance of the small-sized plankton-feeding morph ( Bøhn et al. 2004, Bøhn et al. 2008). Clearly, the existence of different morphs of whitefish in a lake is contingent on ecological opportunity driven by habitat availability and presence of competitors and predators. Whitefish may have a very diverse ecological niche, and may therefore also impact on other freshwater species. This potential interactions with other species have also been investigated to some degree, in particular the interaction with Arctic char has received some interest ( Amundsen et al. 2010, Eloranta et al. 2011, Sandlund et al. 2016a).

The whitefish has been repeatedly translocated in Norway, and it is unclear what is a naturally recruited population or what is due to human translocation (Sandlund et al. 2013b, c). It would be interesting to use modern genetic methods to try to investigate this. This should be possible as more and more high quality genomes are published, also for various Coregonus species (Merot et al. 2022).

On average, more than two papers focusing on whitefish biology has been published per year, and the publication rate has been stable throughout the time period investigated (slope estimate 0.03±0.02 year-1). Overall, the biology should be well understood, but given the phenotypic and genetic diversity present a full understanding is eluding us. In a biodiversity context, a complete understanding as well as a Scandinavian agreement on the taxonomic status of the different populations/morphs is needed.