Table 2.
Examples of means for reducing genetic and other risks associated with captive breeding programs.
| Means for reducing genetic or other risks associated with captive breeding programs | Outcome/benefit | References |
|---|---|---|
| Minimize generations in captivity | Reduces domestication selection to captivity Reduces the potential loss of genetic diversity in captivity | Frankham et al. (2002); Frankham (2008) |
| Minimize intentional selection in captivity (e.g., large adult size, early spawning adults) | Reduces domestication selection to captivity Early release of offspring; use broodstock with wild exposure or from the wild | Miller and Kapuscinski (2003); Frankham et al. (2002); O'Reilly and Doyle (2007) |
| Use local populations for captive breeding and/or supplementation | Reduces the loss of adaptation to local environments Prevents outbreeding depression | Brannon et al. (2004) |
| Restrict captive-rearing to life-history stages where natural mortality in the wild is not as severe | May reduce domestication selection in captivity | P. O'Reilly, DFO Halifax, Canada, personal communication |
| Maintain Ne as high as possible | Reduces the loss of genetic diversity in captivity | Ryman and Stahl (1981); Tave (1984); Allendorf and Ryman (1987); Withler (1988); Eknath and Doyle (1990); Allendorf (1993); Doyle et al. (2001); Frankham et al. (2002); Campton (2004); Rodriguez-Ramilo et al. (2006); O'Reilly and Doyle (2007); Wedekind et al. (2007) |
| Start the initial captive broodstock with as many genetically-diverse founders as possible | ||
| Equalize founder representation in the initial captive broodstock | ||
| Equalize family sizes in captivity and at time of release | ||
| Equalize sex ratios at spawning | ||
| Recover offspring from each spawning adult at each sampling event before release at in each spawning year | ||
| Equalize captive population sizes across generations | ||
| Maximize captive generation length | ||
| Do not carry out mixed-sperm fertilizations | ||
| Allow free mate choice rather than conduct random matings | May improve offspring quality and retention of fitness | Fleming (1994); Wedekind 2002; Berejikian et al. (2004); Pitcher and Neff (2007) |
| Minimize family variance in the captive component relative to the wild component of the population | Potentially increases Ne of the whole population | Ryman and Laikre (1991); Hedrick et al. (2000a,b); Wang and Ryman (2001) |
| Apply sperm cryopreservation techniques, or surrogate broodstock technologies | Maximizes generation length, thereby potentially reducing the loss of genetic diversity and loss of fitness (from domestication selection or a relaxation of natural selection) in captivity | Okutsu et al. (2007); O'Reilly and Doyle (2007) |
| Greater naturalization of the captive environment (for physiological, morphological and behavioural conditioning) | Improves survival chances upon exposure to the wild | Maynard et al. (1996, 2004); Braithwaite and Salvanes (2005); Salvanes and Braithwaite (2005) |
| Estimate relatedness among founders and use this information, as well as employ pedigree analyses, to minimize/avoid kin matings | Reduces inbreeding and retains genetic diversity | Fernandez and Caballero (2001); Fernandez et al. (2003); Hansen and Jensen (2005); Herbinger et al. (2006); O'Reilly and Doyle 2007; Kozfkay et al. (2008) |
| Optimal releases of captive-reared individuals into the wild (e.g. at proper times, body sizes, water temperatures) | Improves survival chances upon exposure to the wild | Miller and Kapuscinski (2003); Brannon et al. (2004); O'Reilly and Doyle (2007) |
| Grow captive-reared individuals at ‘natural’ rates of growth | Decreases sex ratio skews brought on my early male maturation | Larsen et al. (2004) |
| Monitor success of released captive-bred individuals | Feedback for improvement of captive-breeding programs | Flagg et al. (2004a); O'Reilly and Doyle (2007) |
| Delay maturation of individuals in captivity | Extend generation length in captivity | Frankham et al. (2002) |
Discussions of many of these with specific respect to salmonid fishes can also be found in Miller and Kapuscinski (2003), Reisenbichler et al. (2003), Flagg et al. (2004b) and O'Reilly and Doyle (2007).