The winter before spawning season, the gonads of both sexes increase in size and weight. The ovaries in females also begin to develop and mature certain eggs to get them ready for fertilization. Adult flounders migrate offshore during the winter to breed in deeper, coastal areas over the winter and spring months. Although the breeding season is long, lasting at least six months, the flounder only spawn once during this period, before beginning the summer migration back to an estuarine habitat.