Life history features of the nonindigenous three-spined stickleback (Gasterosteus aculeatus Linnaeus, 1758) in the Gomishan wetland (southeast Caspian Sea, Iran)

The Caspian Sea forms the southern limit of the distribution range of the three-spined stickleback (Gasterosteus aculeatus), but little is known about its life history in this area. A total of 362 specimens were collected from the Gomishan wetland (southeast Caspian Sea, Iran) to describe the stickleback’s life history characteristics. Samples were taken monthly between February and July of 2008. The maximum ages of the population observed were 2+ years for males and 3+ years for females. The length-weight relationship (LWR) was estimated as W = 0.0042TL^3.711 for immature specimens, W = 0.0095TL^3.1328 for males, and W = 0.0057TL^3.4678 for females. The sex ratio was 1:2.63, in favor of females. Reproduction of the three-spined stickleback in the wetland occurred around March-June, with the highest average value of 2.82 for males and of 17.12 for females in April. Two kinds of eggs were found in the ovary: small white opaque eggs with a mean diameter of 0.549, and large yolk-filled eggs with a mean diameter of 1.317. The number of small eggs ranged from 311 to 4709, and of large eggs from 128 to 885. The mean absolute fecundity was 1241.69 eggs, while the mean relative fecundity was 535.24 eggs/g of body weight.