Population fecundity and reproductive habits in Patagonotothen tessellata were established for each reproductive period during 1988 and 1989. Fecundity/total length and fecundity/total weight relationships were analysed through regression models. Fecundity was positively correlated with fish length and weight. Mean fecundity was 25932 eggs (range 7634–62033). The regressions for each reproductive period are similar, suggesting that the amount of energy allocated to reproduction does not vary between spawning periods. Parental behaviour is described from both field and laboratory observations. Nesting and parental care were carried out by P. tessellata males. The life history strategy of this species is discussed in relation to that of other nototheniid species.