POPULATION ECOLOGY Divergent compensatory growth responses within species: linked to contrasting migrations in salmon?

• Main Authors: James D. Eddington, Æ Jeffrey, A. Hutchings
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Atlantic salmon; Salmo salar
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.512.5982; http://myweb.dal.ca/jhutch/publications_pdfs/2007_fra_wei_o.pdf

Abstract Animals often exhibit accelerated or ‘‘com-pensatory’ ’ growth (CG) after periods of environmentally induced growth depression, raising important questions about how they cope with environmental variability. We tested an underexplored hypothesis regarding the evolu-tionary consequences of CG; namely, that natural popula-tions differ in CG responses. Common-garden experiments were used to compare subadult growth following food restriction between groups (control, treatment) of two Atlantic salmon (Salmo salar) populations and their first-generation (F1) hybrids. The populations are found at similar latitudes but characterized by differences in migration distance. We predicted that long-distance mi-grants would better maintain growth trajectories following food restriction than short-distance migrants because they: (1) require larger body sizes to offset energetic costs of migration and (2) face greater time constraints for growth as they must leave non-breeding areas earlier to return to breeding areas. Long-distance migrants grew faster, achieved quicker CG (relative to controls), and their overall body morphology was more streamlined (a trait known to improve swimming efficiency) than slower growing short-distance migrants. F1 hybrids were generally intermediate in ‘‘normal’ ’ growth, CG, and body mor-phology. We concluded that CG responses may differ considerably among populations and that the conditions generating them are likely interconnected with selection on a suite of other traits.