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Northern pike - Esox lucius 

 

MANAGEMENT ISSUES

Summary of issues specific to the Baltic region

The relatively small genetic patch size and a continuous population genetic structure indicate that management on local scales is preferable. Further investigations will show if management on a local scale is preferable in the whole Baltic region.

Current management regulations

The pike is subject to commercial and sport fishery in coastal areas all around the Baltic. Data is currently missing on whether this fishery is affecting the biological diversity of the species. The species has declined locally in some areas around the Baltic (for instance the Kalmar Sund region). This can result in loss of genetic variation, but since genetic diversity is not monitored little is known of such potential effects.

Gaps between management and scientific evidence

Genetic diversity is not considered in present management. The genetic patch size which is estimated to 100-150 km indicates that areas of such approximate sizes are suitable for management of the pike. Similarly, if pike populations are exterminated or drastically reduced locally it can result in loss of genetic variation and in break of genetic exchange within the genetic cline. Genetically healthy Baltic pike populations require the maintenance of spawning areas along the coastlines of the Baltic Sea.

 

GENETIC INFORMATION (January 2012)

Species Number of genetic studies Baltic population structure Baltic population diversity Baltic effective population size Temporal data Genetic risks Management recommendations
Northern pike
1 Continuous Low Unknown No information Loss of local adaptation Management on a local basis. Management units about 100 km.


Mapping Baltic Sea genetic biodiversity 

These maps show mean differentiation of populations, and location of major genetic discontinuities in Northern pike (Esox lucius)

       

Fig 1. Barriers of gene flow

Three major barriers to genetic exchange was observed for the Northern pike.

Full lines are barriers supported by at least half of the scored gene loci. Dotted lines are barriers supported by less than half of the scored loci.

 

Fig 2. Genetic divergence

The degree of genetic divergence among populations was classified.

Red dots: populations more genetically divergent than the average divergence among populations.

Blue dots: populations less genetically divergent than the average.

Peripheral populations are generally more diverged (more genetically unique) than central populations.

These are preliminary results (January 2012). Full and additional results on Baltic Sea genetic biodiversity will be presented in a coming scientific report.  

Summary of key published genetic information

Current knowledge of northern pike population differentiation in the Baltic Sea primarily comes from one study (Laikre et al. 2005). In this study 337 specimens of northern pike were collected from the coastal zones of the central Baltic region and from the Finnish islands of Åland.

Isolation by distance appears important for shaping the genetic structure pike in this region resulting in a largely continuous genetic change over the study area.

Analysis of individual pairwise genotypic data show significant positive genetic correlation among pike collected within geographical distances of less than c. 100-150 km. This "genetic patch size" may be used as a preliminary basis for identifying management units for pike in the Baltic Sea.

A larger ongoing study of northern pike in the Baltic Sea has been launched within the BaltGene project. Within this ongoing study populations from the whole Baltic Sea are sampled and the results will show if the genetic pattern of continuous change is similar in the whole Baltic.

Key publications

Laikre L, Miller LM, Palmé A, Palm S, Kapuscinski AR, Thoresson G and Ryman N (2005) Spatial genetic structure of northern pike (Esox lucius) in the Baltic Sea. Molecular Ecology 14, 1955-1964. PubMed

More information about herring at IUCN  - International Union for Conservation of Nature Resources

 

 

CONTRIBUTORS (January 2012)
Linda LaikreNils Ryman and Lovisa Wennerström, Stockholm University, Sweden


Responsible editor: Linda Laikre, Stockholm University, Sweden
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