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Gymnocephalus cernua (Linnaeus, 1758)

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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: https://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:

Common names from other countries

Classification / Names Common names | Synonyms | Catalog of Fishes(genus, species) | ITIS | CoL | WoRMS | Cloffa

Teleostei (teleosts) > Perciformes/Percoidei (Perchs) > Percidae (Perches) > Percinae
Etymology: Gymnocephalus: Greek, gymnos = naked + Greek, kephale = head (Ref. 45335).
  More on author: Linnaeus.

Environment: milieu / climate zone / depth range / distribution range Ecology

Freshwater; brackish; benthopelagic; pH range: 7.0 - 7.5; dH range: 8 - 12; potamodromous (Ref. 51243); depth range 2 - 85 m (Ref. 121625).   Temperate; 10°C - 20°C (Ref. 13371); 74°N - 43°N, 6°W - 169°E

Distribution Countries | FAO areas | Ecosystems | Occurrences | Point map | Introductions | Faunafri

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.

Length at first maturity / Size / Weight / Age

Maturity: Lm 10.5  range ? - ? cm
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)

Short description Identification keys | Morphology | Morphometrics

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).

Biology     Glossary (e.g. epibenthic)

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).

Life cycle and mating behavior Maturities | Reproduction | Spawnings | Egg(s) | Fecundities | Larvae

Eggs turn adhesive on contact with water and stick to stones or plants. Females lay eggs in two or more portions, usually separated by about 30 days in summer. First portion of eggs is larger the second portion. Larvae without or with only a brief, pelagic larval stage, switching early to benthic life, secretive and solitary, not forming schools. Larval survival is poor below 10°C and above 20°C (Ref. 59043).

Main reference Upload your references | References | Coordinator | Collaborators

Kottelat, M. and J. Freyhof, 2007. Handbook of European freshwater fishes. Publications Kottelat, Cornol and Freyhof, Berlin. 646 pp. (Ref. 59043)

IUCN Red List Status (Ref. 130435)

  Least Concern (LC) ; Date assessed: 01 January 2008

CITES (Ref. 128078)

Not Evaluated

CMS (Ref. 116361)

Not Evaluated

Threat to humans

  Potential pest




Human uses

Fisheries: minor commercial; gamefish: yes; bait: usually
FAO(Fisheries: production; publication : search) | FishSource | Sea Around Us

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Trophic ecology
Food items
Diet compositions
Food consumptions
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Ecology
Ecology
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Max. ages / sizes
Length-weight rel.
Length-length rel.
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Egg(s)
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Anatomy
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Brains
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Physiology
Body compositions
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Swimming type
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Visual pigment(s)
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Diseases / Parasites
Toxicities (LC50s)
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Estimates based on models

Phylogenetic diversity index (Ref. 82804):  PD50 = 0.5312   [Uniqueness, from 0.5 = low to 2.0 = high].
Bayesian length-weight: a=0.00955 (0.00874 - 0.01044), b=3.00 (2.97 - 3.03), in cm Total Length, based on LWR estimates for this species (Ref. 93245).
Trophic level (Ref. 69278):  3.3   ±0.57 se; based on food items.
Resilience (Ref. 120179):  Medium, minimum population doubling time 1.4 - 4.4 years (K=0.1-0.48; tm=1-2).
Fishing Vulnerability (Ref. 59153):  High vulnerability (58 of 100).
Price category (Ref. 80766):   Unknown.