The life history, food habits, feeding and locomotory activity rhythms of the upland bully,PhilypnodonbrevicepsStokell were investigated (February 1969‐March 1970) as a basis for studying the relationships between food consumption, biomass and production of the species in a small, moderately eutrophic lake (one of a pair of adjacent lakes at an altitude of 610m in the South Island, New Zealand, known collectively as Spectacles Lakes). Annuli formed on the scales during August and September and could be used as valid indicators of age, although small fish could be aged simply by length frequency analysis. The maximum life‐span for both sexes was observed to be 4.5 years but growth of males considerably exceeded that of females. Because females matured at a smaller size than males, mature females were in excess of mature males (3.7: 1). Each female laid only one batch of eggs during a short breeding season in spring (October‐December) but several females contributed eggs to each nest. Fecundity ranged from 60–440 eggs per female; the relationship between egg number (F) and length (l) was logF=–1.609+2.314 logland between egg number and age (A)wasF=–93.51+109.93A.Larvae hatched in approximately one month (water temperature 14.4‐17.5°C) and the yolk sac became absorbed after a further eight days. Some fry remained pelagic for up to six months. Fry fed predominantly on Crustacea, but the diet changed to larger insect larvae and young of its own species with increasing age and size of the fish. The diet also varied, but to a lesser extent, with season and the time of day. All age groups showed diel rhythms of feeding and locomotory activity which, however, exhibited complex seasonal phase shifts throughout the year. In general, periods of higher feeding intensity appeared to follow closely the periods of increased locomotory activity. The activity level of larger fish was higher than that o