Denmark country information

Common names: Almindelig hork, Hork
Occurrence: native
Salinity: freshwater
Abundance: common (usually seen) | Ref: Frier, J.-O., 1994
Importance: | Ref:
Aquaculture: | Ref:
Regulations: | Ref:
Uses: no uses
Comments: Occurs throughout the country except Bornholm and Vendsyssel (Ref. 9945). Also Ref. 556.
National Checklist:
Country Information: httpss://www.cia.gov/library/publications/resources/the-world-factbook/geos/da.html
National Fisheries Authority:
Occurrences: Occurrences Point map
Main Ref: Muus, B.J. and P. Dahlstrøm, 1990
National Database:

Classification / Names

Actinopterygii (ray-finned fishes) > Perciformes (Perch-likes) > Percidae (Perches) > Percinae
Common names | Synonyms | Catalog of Fishes (gen., sp.) | ITIS | CoL

Common names from other countries

Ерш обыкновенный, Grémille, Acerina, ... more

Main reference

Kottelat, M. and J. Freyhof. 2007. (Ref. 59043)
References | Biblio | Coordinator | Collaborators

Size / Weight / Age

Max length : 25.0 cm TL male/unsexed; (Ref. 556); common length : 12.0 cm TL male/unsexed; (Ref. 556); max. published weight: 400.00 g (Ref. 556); max. reported age: 10 years (Ref. 59043)

Length at first maturity
L_m 10.5 range ? - ? cm

Environment

Freshwater; brackish; demersal; pH range: 7.0 - 7.5; dH range: 8 - 12; potamodromous (Ref. 51243); depth range 10 - ? m (Ref. 9696)

Climate / Range

Temperate; 10°C - 20°C (Ref. 13371), preferred ?; 74°N - 43°N, 6°W - 169°E

Distribution

Europe: Caspian, Black, Baltic and North Sea basins; Great Britain; north to about 69° N in Scandinavia. Asia: Aral Sea basin, Arctic Ocean basin eastward to Kolyma drainage. Several countries report adverse ecological impact after introduction.
Countries | FAO areas | Ecosystems | Occurrences | Introductions

Short description

Dorsal spines (total): 11 - 19; Dorsal soft rays (total): 11-16; Anal spines: 2; Anal soft rays: 5 - 6; Vertebrae: 35 - 36. Distinguished uniquely from its congeners by its body depth 24-27% SL. Differs further from other members of the genus by the combination of having a flank yellowish with numerous, small, irregular, dark blotches and having 11-16 dorsal spines (Ref. 59043). Caudal fin with 16 to 17 rays (Ref. 40476). Dorsal fins are fused. Color brownish with dark spots (Ref. 35388).

Inhabits eutrophic lakes, lowland and piedmont rivers. Most abundant in estuaries of large rivers, brackish lakes with salinities up to 10-12 ppt and reservoirs. In general, its abundance increases with increased eutrophication (Ref. 59043). Reported to prefer still or slow-flowing water with soft bottom and without vegetation (Ref. 59043) and deep water with deposits of sand and gravel (Ref. 9696). Can tolerate some degradation of the environment (Ref. 30578). Can co-exist in deep lakes with Perca fluviatilis. Both species partly occur at different depths with Gymnocephalus cernua being more abundant in deeper layers (Ref. 59043). The membranous external walls of the head canals of this species provide high directional sensitivity; can feed at night in the dark using the lateral line system; feeds on zooplankton, chironomids, oligochaetes and amphipods (Ref. 10999). Pelagic in coastal lakes and tidal estuaries, preying on zooplankton and fish. Spawns on a variety of substrates at depths of about 3 m or less (Ref. 59043). White to yellow eggs in sticky strands are found on rocks and weed in shallow water (Ref. 41678). Used as bait for pike (Ref. 6258). Females live up to 10 year while males up to 7 years (Ref. 59043).

IUCN Red List Status (Ref. 115185)

Least Concern (LC)

Threat to humans

Potential pest

Human uses

Fisheries: minor commercial; gamefish: yes; bait: usually

More information

Countries
FAO areas
Ecosystems
Occurrences
Introductions
Stocks
Ecology
Diet
Food items
Food consumption
Ration

Common names
Synonyms
Metabolism
Predators
Ecotoxicology
Reproduction
Maturity
Spawning
Fecundity
Eggs
Egg development

Age/Size
Growth
Length-weight
Length-length
Length-frequencies
Morphometrics
Morphology
Larvae
Larval dynamics
Recruitment
Abundance

References
Aquaculture
Aquaculture profile
Strains
Genetics
Allele frequencies
Heritability
Diseases
Processing
Mass conversion

Collaborators
Pictures
Stamps, Coins
Sounds
Ciguatera
Speed
Swim. type
Gill area
Otoliths
Brains
Vision

Tools

Special reports

Check for Aquarium maintenance | Check for Species Fact Sheets | Check for Aquaculture Fact Sheets

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Summary page | Point data | Common names | Photos

Internet sources

Estimates of some properties based on models

Phylogenetic diversity index (Ref. 82805)
PD₅₀ = 0.5312 many relatives (e.g. carps) 0.5 - 2.0 few relatives (e.g. lungfishes)

Trophic Level (Ref. 69278)
3.3 ±0.57 se; Based on food items.

Resilience (Ref. 69278)
Medium, minimum population doubling time 1.4 - 4.4 years (K=0.1-0.48; tm=1-2)

Vulnerability (Ref. 59153)
Low vulnerability (20 of 100)

Price category (Ref. 80766)
Unknown

Gymnocephalus cernua (Linnaeus, 1758)