Physiological parameters

Physiological parameters for zebrafish include environmental factors, general physiological factors and blood values. The normal values for these parameters are listed in the tables below.

In the laboratory, it is important that zebrafish be housed in systems where optimal monitoring and control of water quality can be guaranteed. There are no rigid standards; the parameters in use are guidelines based on the literature and on laboratory experience (see the table under 'Physical environmental factors' for details).

General physiological factors

Factor (unit)


Length and weight of adult fish (from 5-6 months)

30-40 mm; 350-500 mg (females are slightly larger than males)


Up to 66 months (average 42 months); in practice: more welfare and health problems after 24 months

Respiration rate (movements per minute)

80 (gill cover movements)

Number of chromosomes

25 chromosomes (4n)

Sexual maturity

Sexual development: 1-3 months; initially, all individuals are female (juvenile ovaria); then transformation into males (with transformation of juvenile ovaria to testes) or into adult females (maturation of juvenile ovaria into adult ovaria)

Breeding age

After 3 months

Reproductive cycle

Females can produce eggs every few days (depending on their physical condition); for high-quality reproduction and the prevention of health problems, spawning is necessary once a week

Brood size

Dependent on the female’s condition and the particular zebrafish line; ranges from a few to as many as 1000; average: between 100-300 per female


At 28.5 degrees Celsius; embryo (0-72 hrs): larva: >72 hrs post fertilization; first 24 hrs: segmentation, then organogenesis; hatching: 48-72 hrs post fertilization; self-feeding: 120-168 hrs post fertilization

Blood values

The values below are approximations and are derived from various sources.

Hematological parameters (unit)

Values (average ± 1 SD)


Total blood volume (μl/fish)


Based on the maximum obtainable blood sampling volume

hemoglobin (g/dL)

Males: 13.2 ± 0.8

Females: 13.1±1.9


hematocrit (% vol)

Males: 30.9 ± 5.5

Females: 26.7± 4.4

Males and females combined: 31.5 ± 5.7

White blood cells (*1000/mm3)

~ 80

Distribution: lymphocytes (71-92%); monocytes (5-15%); neutrophils (2-18%); eosinophils (0-2%); basophils (0-2%)

Red blood cells (*106/ μl)

3.0 (range 2.9-3.2)


Glucose (mg/dL)

82.2 ± 12.0 (range 62.0-91.0)