Actinopterygii (ray-finned fishes) > Osteoglossiformes
(Bony tongues) > Gymnarchidae
Etymology: Gymnarchus: Greek, gymnos = naked + Greek, archos = anus (Ref. 45335).
Environment: milieu / climate zone / depth range / distribution range
Freshwater; demersal; pH range: 6.5 - 8.0; dH range: 10 - 25; potamodromous (Ref. 51243). Tropical; 23°C - 28°C (Ref. 13614); 18°N - 2°N, 16°W - 36°E
Africa: occurring in the Gambia, Senegal, Niger, Volta and Chad River basins (Ref. 81275), Lake Turkana (Ref. 52331, 82489) and the Baro River drainage (Ref. 58460).
Size / Weight / Age
Maturity: Lm ?  range ? - ? cm
Max length : 167 cm SL male/unsexed; (Ref. 2915); max. published weight: 18.5 kg (Ref. 2915)
Morphology | Morphometrics
(total): 183-230. Body depth 7.2-10.3 x SL. Head 5.6-6.9 x SL. Snout prominent. Pectorals 1.9-5.0 x head length. Body terminates in thin point. Head without scales. Scales small.
Following flooding of the river banks (Gambia River), this species builds large elliptical floating nests in densely vegetated swamps at depths of about 1-1.5 m; lays about 1000 `amber-like' eggs; larvae hatching after 5 days (Ref. 10609). Feeds on crustaceans, insects and fish (Ref. 28714). No pelvic, anal or caudal fins. Possesses an electric organ that extends along almost the entire trunk to the tip of the tail (Ref. 10840). Also equipped with ampullary receptors and two types of tuberous receptors for electroreception (Ref. 10841). Showed increased electric organ discharge (EOD) rate by 50-60 Hz between 21 and 31°C (Ref. 10837). An air-breathing species (Ref. 118411).
Life cycle and mating behavior
Maturity | Reproduction | Spawning | Eggs | Fecundity | Larvae
It breeds in well-vegetated, marginal areas of swamps and rivers, where a large, floating nest, about 1 m in diameter is constructed. Here the eggs are laid and later guarded by one of the parents (Ref. 27583). Distinct pairing (Ref. 205).
Bigorne, R., 1990. Gymnarchidae. p. 185-186. In C. Lévêque, D. Paugy and G.G. Teugels (eds.) Faune des poissons d'eaux et saumâtres d'Afrique de l'Ouest. tome 1. Faune Trop. 28. Musée Royal de l'Afrique Centrale, Tervuren, Belgique and ORSTOM, Paris. (Ref. 2911)
IUCN Red List Status (Ref. 119314)
CITES (Ref. 115941)
Threat to humans
ReferencesAquacultureAquaculture profileStrainsGeneticsAllele frequenciesHeritabilityDiseasesProcessingMass conversion
Estimates of some properties based on models
Phylogenetic diversity index (Ref. 82805
= 1.5000 [Uniqueness, from 0.5 = low to 2.0 = high].
Bayesian length-weight: a=0.00380 (0.00147 - 0.00985), b=3.09 (2.86 - 3.32), in cm Total Length, based on LWR estimates for this (Sub)family-body shape (Ref. 93245
Trophic Level (Ref. 69278
): 3.7 ±0.58 se; Based on food items.
Resilience (Ref. 69278
): Low, minimum population doubling time 4.5 - 14 years (K=0.12-0.17).
Vulnerability (Ref. 59153
): High to very high vulnerability (71 of 100) .