Once eggs are fertilized, they take between 5 and 10 days to hatch, depending on the temperature of the water. Upon hatching, threespine stickleback larvae are about 4 mm in length. The larvae will continue to grow by absorption of the yolk, which they will completely consume about four days after hatching. Approximately nine days after hatching, the larvae reach a length of about 8 mm and assume the shape of the adult fish. This is the juvenile stage, in which the immature young become independent of their father. Juveniles become adults when they reach sexual maturity, which is usually within 1 to 2 years of hatching.
- Swarup, H. 1958. Stages in the development of the stickleback Gasterosteus aculeatus. Development, 6: 373-383.