Life history of Gambusia nobilis (Pecos Gambusia) from Bitter Lake National Wildlife Refuge

Abstract

Relatively little is known about variation in allocation to growth and reproduction of endangered and threatened fish species with small geographic distributions or isolated populations. We examined life history and reproductive variation among four ecologically distinct populations of the federally listed Pecos gambusia, Gambusia nobilis, from sinkholes at Bitter Lake National Wildlife Refuge in New Mexico, United States. Despite ecological variation between sinkholes, there were no significant differences in female reproductive traits between populations. Reproductive strategy shifted over the reproductive season from investment in many small embryos to fewer large offspring. Reproductive effort was not correlated with female size or condition (which varies between populations), suggesting that small or poor quality females invest similarly to larger or healthier females. Reproduction was asynchronous between populations and through the reproductive season. Embryo development patterns suggest that females often carry embryos of two or more developmental stages and provision them during gestation (matrotrophy). Understanding the life history strategies of this endangered species is important to the planning and implementation of conservation efforts.