Changes in Specific Gravity of Atlantic Salmon ( Salmo salar ) Alevins

• Published in: Journal of the Fisheries Research Board of Canada
• Main Authors: Peterson, R. H., Metcalfe, J. L.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1977
• Subjects: General Medicine; Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1139/f77-320; http://www.nrcresearchpress.com/doi/pdf/10.1139/f77-320

The specific gravity of Atlantic salmon (Salmo salar) alevins decreases during posthatching development from 1.067 at hatching to 1.044 at terminal yolk resorption. The water content of the embryo is ca. 84% throughout posthatching development while that of the yolk is ca. 56%. Therefore, as the embryo grows at the expense of yolk material, the water content of the alevin increases during development. This increase in water content can entirely account for the observed change in specific gravity. Alevins reared at lower temperatures have a higher specific gravity for any given embryonic length, implying the presence of more yolk reserves. Splake alevins reared in a hatchery tray had a lower specific gravity at a given length than did alevins reared in gravel or artificial turf substrates. Measurements of specific gravity in conjunction with length measurements during development may be useful in comparing different incubation conditions. Key words: specific gravity, Atlantic salmon, alevin, yolk, embryo, water content, temperature, splake