Life history of Gambusia holbrooki (Pisces, Poeciliidae) in the Ebro delta (NE Iberian peninsula)
- Cite this article as:
- Vargas, M.J. & de Sostoa, A. Hydrobiologia (1996) 341: 215. doi:10.1007/BF00014686
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We studied age, growth and reproduction of an introduced poeciliid, Gambusia holbrooki (Agassiz, 1859), in the Ebro delta marshes. Maximum ages observed were 2+ in females and 0+ in males. Growth commenced in March and continued until September. Females reached greater sizes, had a higher rate of growth and lived longer than males. The largest sizes found were 63 mm ♀♀ versus 32 mm ♂♂. Multiple spawning occurred throughout the reproductive cycle (from May to September). The average brood size per female reached its maximum in July in the parental cohort (86 embryos/♀) and in August in the offspring cohort (29 embryos/♀). After reproduction the parental cohort decreased drastically. The relationship between fecundity (F) and total length (mm) was calculated for each month of the reproductive period. Sex-ratio deviated significantly from unity.
Viviparity, several broods and large larvae provide G. holbrooki with several advantages over oviparous species. The capacity to adjust its life history to a particular environment could explain the life history differences between those in the Ebro delta and other populations.