Diagnosis: Enteromius mimus belongs to the group of species of Enteromius with a flexible last unbranched dorsal fin ray that lacks serrations along its posterior edge (Ref. 127947). Enteromius mimus can easily be distinguished from the other species of this group from the East Coast and Nilo-Sudan ichthyofaunal regions by the following combinations of characteristics: a complete lateral line vs. an incomplete lateral line in E. atkinsoni, E. pumilus, E. serengetiensis, E. tongaensis and E. toppini; two pairs of barbels vs. one pair in E. pseudotoppini, and no barbels in E. anema and E. profundus; one to three dark spots on the flanks, which sometimes fuse into a mid-lateral line in preserved specimens, starting posterior to the operculum vs. a dark line running from the tip of the snout to the caudal fin base in E. bifrenatus and E. yongei, and a thin dark line from the beginning of the operculum to the caudal fin base in E. viviparus; 11-12 scales around the caudal peduncle vs. 8 in E. leonensis, 9-10 in E. venustus, and 10 in E. magdalenae and E. yeiensis; 24-27 lateral line scales vs. 30 in E. lineomaculatus, and 31 in E. innocens; 3.5-4.5 scales between the dorsal fin base and the lateral line vs. 5.5 in E. unitaeniatus and 6 in E. usambarae; 3-4 scales between the lateral line and the pelvic fin vs. 2 in E. trispilopleura, and 2-2.5 in E. neglectus; 7-8 branched dorsal fin rays vs. 9 in E. quadripunctatus; a body depth which is larger than the head length vs. a body depth which is equal to the head length in E. nigeriensis; a smaller snout length, 4.1-7.1% of standard length vs. 7.1-10.1% in E. radiatus (Ref. 127947). It differs from E. perince by a combination of a lower number of lateral line scales, 24-27 vs. 29-30, a lower number of scales between the dorsal fin base and lateral line, 3.5-4.5 vs. 5.5, a lower number of scales around the caudal peduncle, 11-12 vs. 14, a smaller interorbital width, 6.3-8.3% of standard length vs. 9.8-10.2%, a larger pre-pectoral distance, 26.0-29.0% of standard length vs. 23.1-24.5%, a lower minimum caudal peduncle depth, 11.1-14.0% of standard length vs. 15.0-16.4%, a lower maximum caudal peduncle depth, 12.9-16.5% of standard length vs. 17.7-19.4%, and a smaller anal fin base length, 7.3-8.7% of standard length vs. 8.5-9.6% (Ref. 127947). It differs from E. stigmatopygus by a combination of a smaller pre-pectoral distance, 26.0-29.0% of standard length vs. 29.1-33.1%, and a larger anal fin length, 18.0-19.7% of standard length vs. 12.6-17.4% (Ref. 127947). Enteromius mimus differs from E. alberti by a lower number of lateral line scales, 24-27 vs. 27-34, a larger pre-anal distance, 68.4-74.8% of standard length vs. 65.1-73.0%, a smaller post-anal distance, 16.3-19.3% of standard length vs. 16.3-24.2%, a larger body depth, 26.5-34.3% of standard length vs. 21.7-31.2%, a larger head depth, 17.8-21.8% of standard length vs. 15.1-19.0%, and a larger pelvic fin length, 18.2-22.4% of standard length vs. 15.0-20.9% (Ref. 127947). Specimens from E. mimus differ from the specimens of the population of E. cf. mimus from the Lake Edward system by a lower number of scales between the origin of the dorsal fin and the lateral line, 3.5-4.5 vs. 3.5-4.5, a larger pelvic fin length, 18.2-22.4% of standard length vs. 14.4-21.3%, a smaller snout length, 4.1-7.1% of standard length vs. 4.6-8.3%, a smaller interorbital width, 6.3-8.3% of standard length vs. 6.9-9.9%, a larger post-dorsal distance, 34.8-40.4% of standard length vs. 31.0-39.9%, and a larger anal fin length, 18.0-19.7% of standard length vs. 14.4-21.8% (Ref. 127947).

Description: Body fusiform, largest depth anterior to dorsal fin; dorsal profile from tip of snout to origin of dorsal fin slightly convex, slightly tapering to base of caudal fin; ventral profile from operculum to origin of pelvic fin slightly convex, slightly tapering to posterior end of anal fin base, then slightly concave to caudal fin (Ref. 127947). Head small; eye large and round, located laterally, closer to tip of snout than distal margin of operculum, interorbital profile slightly convex; snout rounded; mouth subterminal; two pairs of barbels, anterior barbel shorter than posterior with anterior one usually reaching up to vertical through the middle of the eye, while posterior one can reach the vertical through posterior margin of pre-operculum (Ref. 127947). Dorsal fin with 3 unbranched and 7 to 8 branched rays, distal margin slightly concave, origin located on vertical through pelvic fin insertion or slightly anterior , 1 lateral line scale; first branched dorsal fin ray longest, posterior rays decreasing progressively in size; pectoral fin with 1 unbranched and 12-14 branched rays, distal profile straight to slightly convex, not reaching anterior base of pelvic fin; pelvic fin with 1 unbranched and 7 branched rays, distal margin convex; anal fin with 3 unbranched and 5-6 branched fin rays, distal margin concave; caudal fin forked with outer rays twice as long as median ones and both lobes rounded and of similar size (Ref. 127947). Anus and urogenital opening situated immediately in front of anal fin base (Ref. 127947). Scales cycloid rounded and radially striate; lateral line completely pored with many lateral line scales, 24-27, gently curved downwards over abdomen but running straight along middle of caudal peduncle and ending at base of caudal fin; scales between dorsal fin and lateral line 3.5-4.5, predorsal scales 9-10, circumpeduncular scales 11-12, scales between lateral line and pelvic fin 3-4, scales between lateral line and belly 3.5-4.5 (Ref. 127947).

Colouration: No sexual dimorphism is observed (Ref. 127947). No information of in vivo colour pattern is available (Ref. 127947). In preserved specimens, overall background colour of body brown, darker dorsally; one to three dark spots on flanks on thick silvery midlateral band; spots fused into mid-lateral line in some specimens, overlying silvery band and starting posterior to operculum; first spot situated anterior to dorsal fin origin, median one below or somewhat anterior to last ray of dorsal fin and last one at caudal fin base (Ref. 127947).