Captive breeding and subsequent releases into the wild are among techniques used for endangered fish species conservation. This paper describes captive breeding methods and reviews establishment of breeding stocks of rare fish endemic to arid ecosystems of the Mediterranean basin, southwest USA and Mexico.
A review was undertaken of captive breeding programmes (some involving reintroductions), focusing primarily on arid zone endemic fishes of southwest USA. Examples of several undertaken since the early 1970s to safeguard endemic American cyprinids, poeciliids and cyprinodontids are presented.
In the USA, about 35 fish species from arid southwestern regions were identified as in need of captive rearing to protect them from extinction. Captive breeding programmes for eight species are summarized.
Colorado squawfish Ptychocheilus lucius - formerly widespread in the Colorado River Basin, there was a large decline in the 1970s due to dam construction. From July 1973 to June 1988, 75 wild adults were kept in raceways or ponds. Breeders caught in 1973 spawned in raceways in 1974, producing small numbers of fry. Subsequent artificial methods (hormonal induction and hand-stripping) produced large numbers of young (up to 0.6 million fry in 1977). Reintroduction commenced in 1985 (over 100,000 alevins released in 1987).
Bonytail Gila elegans - formerly widespread in the Colorado River system but thought close to extinction in the early 1970s due to dam construction. From 1976 to 1988, 34 wild breeding individuals were held in captivity. In 1981, some (receiving hormonal treatment) sexually matured and artificial spawning produced fry. These reached maturity in a pond in 1988 and then bred naturally. From 1981 to 1987, 110,000 fish were released into natural habitat and ‘acclimatised’.
Chihuahua chub G.nigrescens - endemic to Guzman Basin, Mexico. Ten wild individuals in 1978 were placed in ponds where they reproduced but at a very low rate (387 captive fish in 1987). Reintroduction was attempted at one extirpated site.
Woundfin Plagopterus argentissimus - endemic to the Colorado River, but extirpated from most of its historic range. Approximately 1,000 were brought into captivity between 1978 and 1987. Natural and artificial reproduction methods produced small number of offspring. No reintroduction attempts were made due to an Asian tapeworm harbored by captive fish.
Leon Springs pupfish Cyprinodon bovinus - endemic to Leon Creek, Texas. A founder population of 80 adults was established in 1976 in 0.1-0.2 ha ponds where 1,000 young were produced after a year in captivity.
Commanche Springs pupfish C.elegans - endemic to springs (and also found in irrigationcanals) in Texas. A 1974 founder population of 40 adults placed in 0.1-0.2 ponds, successfully reproduced.
Desert pupfish C.m.macularius - a founder stock reproduced in ponds. Ten releases using pond-reared fish were made to natural or semi-natural habitats within and outside their historic range, three reported as successful.
Pecos gambusia Gambusia nobilis - endemic to springs in Pecos River Basin, Texas. A founder stock of 30-40 wild fish was established in ponds in 1974. More than 1,000 young each year for 6 years were produced.
Captive breeding appears an effective short-term measure for rescuing some fish species from extinction. However, it is considered only a temporary measure unless reintroduction of captive-bred individuals into suitable habitat is successful. Monitoring to establish reintroduction success is some times lacking.
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