Diagnosis: Species with a piscivorous morphology; eye large, eye diameter 30.0-31.5% of head length; outer oral teeth few and large, 25-37; dominant males light grey with a black head and a bright red anal fin (Ref. 126312). Amongst piscivorous species from the Lake Edward system, H. aquila differs from H. latifrons, H. mentatus, H. rex, H. simba, and H. glaucus by a larger eye, eye diameter 30.0-31.5% of head length vs. 22.2-29.9%; it further differs from H. latifrons and H. mentatus by a shorter caudal peduncle, caudal peduncle length 14.6-15.4% of standard length vs. 15.7-18.0%; further from H. latifrons by the absence vs. presence of a well-defined mid-lateral band; further from H. mentatus by dominant males uniformly light grey vs. yellow-green with a red anterior part of flank; it further differs from H. rex by a shallower lacrimal, lacrimal depth 17.0-19.1% of head length vs. 18.9-22.5%; and dominant males light grey with black operculum and snout vs. cream-coloured with an orange operculum and a light blue snout; it further differs from H. simba by a larger number of scales between first anal-fin spine and upper lateral line, 12-15, raraely 11, vs. 9-11; an absent vs. strongly developed mental prominence; and dominant males light grey with a black head vs. uniformly yellow with an orange anterior part of flank; it further differs from H. glaucus by a broader head, head width 40.1-43.7% of head length vs. 38.9-40.9%; and dominant males light grey with bright red anal and caudal fins vs. light blue with crimson anal and caudal fins (Ref. 126312). It differs from H. kimondo, H. falcatus, H. curvidens, H. pardus, H. quasimodo and H. squamipinnis by the combination of large vs. small outer oral teeth and smaller number of outer upper jaw teeth, 25-37 vs. 39-79; it further differs from H. kimondo, H. falcatus and H. quasimodo by absence vs. mostly presence of a well-defined mid-lateral band and dominant males light grey with a black head vs. grey dorsally and yellow ventrally, olive-green with an orange-red anterior part of flank, or light grey dorsally and blue-black ventrally; further from H. kimondo by a narrower head, head width 40.1-43.7% of head length vs. 42.9-48.0%; it further differs from H. curvidens and H. pardus by a deeper cheek, cheek depth 26.8-30.8% of head length vs. 20.8-24.9%; further from H. pardus by dominant males light grey vs. speckled to uniformly black; it further differs from H. squamipinnis by larger eyes, eye diameter 30.0-31.5% of head length vs. 23.1-29.7%; and dominant males light grey vs. slate blue (Ref. 126312).

Description: Body shallow and oval (Ref. 126312). Head long, narrow, and with a straight to gently convex dorsal outline; interorbital area narrow; eye average in size in comparison to generalised H. elegans, but large for a piscivorous species; cheek deep; lacrimal average in depth (Ref. 126312). Snout average in length, rounded in dorsal view, narrow, relatively blunt, and slopes gently at 35-45°; premaxillary pedicel long and (strongly) prominent;; jaws isognathous to weakly prognathous, long, narrow, and rounded in dorsal view; gape large and slopes at 25-35°; maxilla extends to vertical through anterior margin of pupil; lower jaw relatively stout and with straight ventral outline in lateral view, mental prominence absent or weakly developed, and lower jaw side nearly flat with an inclination of 25-35° to horizontal in anterior view; upper jaw expanded anteriorly; lips and oral mucosa relatively large (Ref. 126312). Neurocranium average in depth, ethmo-vomerine block decurved, preorbital region shallow, 18-24% of neurocranium length, orbital region average in depth, 30-33% of neurocranium length, and supraoccipital crest shallow and wedge-shaped (Ref. 126312). Outer oral teeth few, unicuspid, and very large; necks stout, conical, and straight; crowns straight to weakly recurved and acutely pointed; dental arcades with anterior half expanded laterally; outer teeth widely and irregularly set with neck-distances of 1-4 neck-widths; no enlarged teeth posterior in upper jaw; inner teeth small, recurved, a mixture of unicuspid and weakly tricuspid, weakly tricuspid rare in large specimens larger than 100mm standard length, and acutely pointed in all specimens; tooth bands very slender crescent-shaped with 1-2 rows of inner teeth, and narrow posteriorly until only outer row remains past 3/4 length of tooth band in upper jaw, past 2/3 length of tooth band in lower jaw; inner teeth closely and regularly set on 1 outer neck-width from outer row; implantation recumbent; size uniform throughout tooth band (Ref. 126312). Lower pharyngeal bone long, very narrow, slim, and shallow over whole length; pharyngeal teeth relatively large and slender; major cusps acutely pointed; cusp gaps concave; minor cusps and cusp protuberances very small; teeth in two median longitudinal rows equal in size and form to lateral teeth, 12 in each row; posterior transverse row with 16-17 teeth, implanted erectly with a lateral inclination; major cusps nearly straight, bluntly pointed, and laterally compressed; minor cusps mostly absent (Ref. 126312). Chest scales small; transition to larger flank scales gradual; minute scales on proximal half of caudal fin; scales on longitudinal line 32-35, scales on upper lateral line 20-23, scales on lower lateral line 10-14, scales between dorsal fin and upper lateral line 5-7, scales between upper lateral line and anal fin 11-15, scales around caudal peduncle 17-20, scales between pectoral and pelvic fins 3-5, infraorbital cheek scales 3-5, postorbital cheek scales 9-12 (Ref. 126312). Caudal fin emarginate; dorsal and anal fins reach to between verticals through caudal-fin base and two scales anterior to this vertical; pectoral fin reaches to between genital opening and second anal-fin spine; pelvic fin reaches to genital opening in females, to between first and second anal-fin spines in males; first pelvic fin ray slightly elongated in all specimens (Ref. 126312). Ceratobranchial gill rakers in outer row of firt gill arch short, stout, and simple; posteriormost rakers anvil-shaped or bifid; epibranchial gill rakers slender and simple (Ref. 126312).

Colouration: Colouration in life of dominant males: body metallic grey; dorsum greyish; belly speckled black; chest, cheek, snout, lower jaw, and lips black; eye with (dark) grey outer ring and golden inner ring; nostril, interorbital, and lacrimal stripes very faint; pectoral fin hyaline, pelvic fin black; dorsal fin sooty and with black lappets; anal and caudal fins bright red and with dusky bases; anal fin with dusky posterior part and 1-2 large orange egg-spots with dusky rings (Ref. 126312). Colouration in life of females and juveniles: body and dorsal part of head silver with yellowish sheen; belly, chest, operculum, cheek, lower jaw, and lips white; snout dusky; eye with (dark) grey outer ring and silver inner ring; nostril and interorbital stripes faint; pectoral fin hyaline, pelvic fin white; dorsal and caudal fins dusky; dorsal fin with black lappets; caudal fin with a yellowish base and a faint red distal part; anal fin yellow with a red sheen (Ref. 126312). Preserved colouration: body brown; dorsum dark brown; ventral part of body and operculum yellowish; chest and lower jaw black in males; cheek yellowish in females, dark-brown in males; snout dusky; nostril and interorbital stripes faint; lacrimal stripe narrow and well-defined; mental blotch present; vertical preopercular stripe well-defined in males; pectoral fin yellowish with blackish first rays in females, black in males; dorsal fin dusky and with black lappets and maculated posterior part; anal fin yellowish with a dusky overlay and, in males, with black lappets and 1-2 large egg-spots; caudal fin with a dusky base, a hyaline distal part, and, in males, whole ventral half hyaline (Ref. 126312).