Siluranodon auritus (Geoffroy Saint-Hilaire 1809)

Diagnosis: 67-87 anal-fin rays; 49-60 thin and flexible gill rakers on lower limb of first gill arch; 4 pairs of well developed barbels; small, spineless dorsal fin with 4-5 branched rays; jaws and palatine bones entirely without teeth (Ref. 43912, 57127).Description: 9-10 branched pectoral fin rays; 44-47 non-fused vertebrae; 10-13 branchiostegal rays on one side of head; posterior nostrils always closer to each other than anterior ones; caudal peduncle considerably deeper than long; inner side of pectoral spine without serrations; caudal and anal fin sometimes continuous; barbels well developed; nasal barbel at least reaching to anterior border of opercle and at maximum to just beyond opercle; maxillary barbel reaches at least to just beyond opercle and at maximum to midway along pectoral spine; inner and outer mental barbels very well developed, about equal in length, or inner pair very slightly longer, at least reaching to base and at maximum to end of pectoral spine; head rounded; caudal moderately forked; pectoral fins broad and rounded, pelvic fins small and pointed; gill rakers covered with filtrating epithelium of micro-rakers (Ref. 43912).Coloration: in live fish as well as in preserved specimens, coloration resembles that of juveniles of Schilbe intermedius: head and back brown; dark band along lateral line, another above anal fin, and a third on anal-fin margin; other fins slightly mottled with brown (Ref. 43912, 57127). Large brown blotch behind head, where swim-bladder lies close below skin; presence of a red spot, shot with gold, on gill cover may be related to maturity state (Ref. 43912).

Distinct pairing (Ref. 205).

Potamodromous. Migrating within streams, migratory in rivers, e.g. Saliminus, Moxostoma, Labeo. Migrations should be cyclical and predictable and cover more than 100 km.

Dorsal spines (total): 0; Dorsal soft rays (total): 5; Anal spines: 0; Analsoft rays: 67 - 87

In the Sudd, it occurs beneath fringing Eichornia. Stomachs of fish examined contained zooplankton, chironomids and debris (Ref. 28714).

Pelagic, occurs large and moderate lakes and rivers (Ref. 43912). In the Sudd, they occur beneath fringing Eichornia (Ref. 28714). Microphagous, feeding mainly on algae and occasionally rotifers, planktonic and benthic crustaceans, immature insects (Ref. 43912) and mud/debris (Ref. 28714, 43912). Probably reproduces during the floods, migrating from lakes to rivers; howver in Lake Kainji fish were reported to migrate from the river to the Lake to spawn (Ref. 43912). Oviparous, eggs are unguarded (Ref. 205). Max. reported total length 175 mm (Ref. 3570, 43912). Might locally represent an important species for fisheries since it is sometimes extremely abundant, but this may be negated by its small size (Ref. 43912).

fisheries:

Siluranodon auritus is the only species in the genus Siluranodon of the catfish (order Siluriformes) family Schilbeidae.

This species is known from the Nile River and the Chad, Niger, Volta, and Comoe basins. In the Sudd, these fish have been found to occur beneath fringing Eichhornia.

Although it has been previously thought that fish of this species lack teeth, it has been found that they have very reduced teeth. As the fish grows, teeth on the upper jaw are lost due to damage, while teeth on the lower jaw are overgrown by the surrounding bone. It has been suggested that this species exhibits pedomorphosis, that is, they retain many juvenile traits into adulthood. Some of these include an absence of a dorsal fin spine and a reduced number of ribs. S. auritus reaches a length of about 17.5 centimetres (6.9 in) TL.

As adults, S. auritus are filter-feeders, feeding primarily on phytoplankton and zooplankton. Stomachs of fish have been examined to contain zooplankton, chironomids and debris.

These fish are oviparous and the eggs are unguarded.