otoliths from 447 mature and 308 immature Oreochromisrnniloticus (10 to 304 mm total length) from Lake Hayq werernmeasured and examined for translucent and opaque macrozones.rnMicrozone analysis was also conducted on the 308 immaturernO. niloticus otoliths. Macrozonal daily age estimate wasrndetermined by extrapolating the number of days between therndate of capture and calender birth dates. utilization of thernnumber of macrozones, condition on the edge of otoliths andrndate of capture enabled the separation of fish intornrecruitment groups. Microzones on the otoliths werernenumerated and used as a measure of age in days and to hindrncast hatch dates. The relationship between otolith size andrnfish total length 11as also examined.rnIt appears that the breeding of o.niloticus in Lake Hayq isrncontinuous with high peaks during !Â·larch-May and July-October.rnTwo translucent macrozones '''ere formed per year duringrnJanuary-February and June-July. Fish spa~ned between Januaryrnand May and July and November of the same year form the firstrntranslucent zone associated with biannuli at different times.rnThe close agreement between macrozonal and microzonal dailyrnage estimates (r=O. 84) sUbstantiates the usefulness macrozonernanalysis to assess the age of O.niloticus. There was a strongrnlinear relationship between otolith size and fish size andrnalso between microzone count and fish length. HOI-leVer, arnlinear relationship underestimates fish size at later ages.rnValues of size-at-age estimates obtained from macro zone and microzone analysis and fish total length-otolith radiusrnrelationship were close to each other. This demonstrates thernusefulness of results from the latter method in supportingrnconclusions drawn from macrozone and microzone analysis.