Genetic effects of long-term stock enhancement programs

Compromising genetic diversity in the wild: unmonitored large-scale release of plants and animals

“…Unintended introduction of the parasite Gyrodactylus salaris with Atlantic salmon from Sweden used in aquaculture caused the collapse of wild salmon populations in many Norwegian rivers [60], exemplifying loss of diversity not associated with gene flow from introduced populations. Loss of alleles in the natural population following gene flow from commercial releases is reported for red sea bream in Japan [61]. Figure I.…”

Selection and genetic drift in captive versus wild populations: an assessment of neutral and adaptive (MHC-linked) genetic variation in wild and hatchery brown trout (Salmo trutta) populations

“…Interest has grown concerning the genetic changes that arise during captivity, especially those that may be disadvantageous in natural environments (Kitada et al 2009). Frankham et al (2002) summarise these changes to include: (1) loss of genetic diversity, (2) inbreeding depression, (3) accumulation of mildly deleterious mutations, and (4) genetic adaptation to captivity.…”

Managing the Genetic Resources in the Intensive Stock Enhancement Program Carried out on Black Sea Bream in Hiroshima Bay, Japan

“…Interestingly, levels of genetic diversity in Hiroshima Bay were similar to other locations where stocking activities had never been conducted (Jeong et al, 2003) and black sea bream was suggested to comprise a large panmictic stock in western Japan. Reviewing the only two large-scale marine stock enhancement programs conducted worldwide over multiple generations and where data on the catches and genetic diversity of wild and hatchery-released fish have been monitored, Kitada et al (2009) emphasized the importance of replacing the broodstock annually. The panmictic genetic structure, large population size and gene flow of red sea bream (Pagrus major) inhabiting Kagoshima Bay, Japan, was suggested to contribute to attenuate the genetic differentiation resulted from producing the hatchery-released offspring from the same small broodstock over several years.…”

“…Ryman & Laikre (1991) warned that in a successful stock enhancement program, the increment in the portion of hatchery-reared offspring may reduce the total effective population (wild and hatchery) and favor inbreeding. However, in their review of marine fish stocking programs, Kitada et al (2009) found no evidence of long-term negative effects of large-scale releases on fitness in the wild population. Furthermore, the minimal kinship approach (Doyle et al, 2001), collecting several batches of eggs over the spawning season (Nugroho & Taniguchi, 2004) or at different time intervals over a single night (Blanco Gonzalez et al, 2010) have proven promising results to increase Nb and minimize the loss of genetic diversity.…”