Hatching time and alevin growth prior to the onset of exogenous feeding in farmed, wild and hybrid Norwegian Atlantic salmon

• Published in: PloS one Vol. 9; no. 12; p. e113697
• Main Authors: Solberg, Monica Favnebøe, Fjelldal, Per Gunnar, Nilsen, Frank, Glover, Kevin Alan
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.12.2014; Public Library of Science (PLoS)
• Subjects: Animal behavior; Animals; Animals, Domestic; Animals, Wild; Aquaculture; Aquatic sciences; Biology; Biology and Life Sciences; Body Size; Chimera; Competition; Degree-days; Domestication; Earth Sciences; Ecology; Ecology and Environmental Sciences; Eggs; Farms; Feeding; Feeding Behavior; Female; Females; Fish hatcheries; Fisheries; Genetic diversity; Genetic Variation; Gravel; Growth; Growth rate; Hatching; Life Cycle Stages; Life history; Male; Oncorhynchus keta; Oncorhynchus kisutch; Population genetics; Rivers; Salmo salar; Salmo salar - physiology; Salmon; Salmonidae; Salmonids; Shellfish; Size effects; Spawning; Time Factors; Water temperature; Zoology; Norway
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0113697

The onset of exogenous feeding, when juveniles emerge from the gravel, is a critical event for salmonids where early emergence and large size provide a competitive advantage in the wild. Studying 131 farmed, hybrid and wild Norwegian Atlantic salmon families, originating from four wild populations and two commercial strains, we investigated whether approximately 10 generations of selection for faster growth has also resulted in increased somatic growth prior to the onset of exogenous feeding. In addition, we tested whether relaxed selection in farms has allowed for alterations in hatching time between farmed and wild salmon. Across three cohorts, wild salmon families hatched earlier than farmed salmon families, while hybrid families displayed intermediate hatching times. While the observed differences were small, i.e., 1-15 degree-days (0-3 days, as water temperatures were c. 5-6°C), these data suggest additive genetic variation for hatching time. Alevin length prior to exogenous feeding was positively related to egg size. After removal of egg size effects, no systematic differences in alevin length were observed between the wild and farmed salmon families. While these results indicate additive genetic variation for egg development timing, and wild salmon families consistently hatched earlier than farmed salmon families, these differences were so small they are unlikely to significantly influence early life history competition of farmed and wild salmon in the natural environment. This is especially the case given that the timing of spawning among females can vary by several weeks in some rivers. The general lack of difference in size between farmed and wild alevins, strongly suggest that the documented differences in somatic growth rate between wild and farmed Norwegian Atlantic salmon under hatchery conditions are first detectable after the onset of exogenous feeding.