Rapid Evolution of Egg Size in Captive Salmon

• Published in: Science (American Association for the Advancement of Science) Vol. 299; no. 5613; pp. 1738 - 1740
• Main Authors: Heath, Daniel D., Heath, John W., Bryden, Colleen A., Johnson, Rachel M., Fox, Charles W.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 14-03-2003; The American Association for the Advancement of Science
• Subjects: Animal reproduction; Animal, plant and microbial ecology; Animals; Applied ecology; Aquaculture; Attrition (Research Studies); Biological and medical sciences; Biological Evolution; Body Constitution; Body Weight; Brackish; Breeding; Chinook salmon; Company growth; Conservation of Natural Resources; Conservation, protection and management of environment and wildlife; Egg masses; Eggs; Environment; Evolution; Fecundity; Female; Female animals; Fertility; Fish hatcheries; Fish-culture; Fisheries; Freshwater; Fundamental and applied biological sciences. Psychology; Genetic aspects; Growth; Marine; Mortality; Oncorhynchus tshawytscha; Ovum - physiology; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; Population mean; Population size; Salmon; Salmon - genetics; Salmon - physiology; Salmonidae; Selection, Genetic; Topology; British Columbia; Salmonidae; Biometrics; Oncorhynchus tshawytscha; Egg; Wild animal; Reintroduction; Freshwater environment; Restocking; Vertebrata; Natural environment; Efficiency; Pisces; Captivity; Rearing; Animal conservation; Environmental protection; Adaptation
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1079707

Captive breeding and release programs, widely used to supplement populations of declining species, minimize juvenile mortality to achieve rapid population growth. However, raising animals in benign environments may promote traits that are adaptive in captivity but maladaptive in nature. In chinook salmon, hatchery rearing relaxes natural selection favoring large eggs, allowing fecundity selection to drive exceptionally rapid evolution of small eggs. Trends toward small eggs are also evident in natural populations heavily supplemented by hatcheries, but not in minimally supplemented populations. Unintentional selection in captivity can lead to rapid changes in critical life-history traits that may reduce the success of supplementation or reintroduction programs.