Gymnarchus niloticus Cuvier, 1829
Aba
photo by John Appleby

 Family:  Gymnarchidae (Abas)
 Max. size:  167 cm SL (male/unsexed); max.weight: 19 kg
 Environment:  demersal; pH range: 6.5 - 8; dH range: 10 - 25, potamodromous
 Distribution:  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).
 Diagnosis:  Dorsal spines (total): 0-0; Dorsal soft rays (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.
 Biology:  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).
 IUCN Red List Status:   (Ref. 96402)
 Threat to humans:  harmless
 Country info:   
 

 Entered by: Binohlan, Crispina B. - 08.07.91
 Modified by: Froese, Rainer - 27.11.03
 Checked by: Froese, Rainer - 05.02.94

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