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Rapid senescence in pacific salmon.
Yolanda E Morbey1, Chad E Brassil, Andrew P Hendry
1Department of Zoology, Ramsay Wright Zoological Laboratories, University of Toronto, 25 Harbord Street, Toronto, Ontario M5S 3G5, Canada. yolanda.morbey@mnr.gov.ca
The American Naturalist
|October 15, 2005
Summary
Pacific salmon exhibit significant variation in senescence, influenced by environmental factors and arrival time. Early arrivals show slower aging, challenging some evolutionary predictions regarding predation and senescence rates.
Area of Science:
- Evolutionary biology
- Gerontology
- Ecology
Background:
- Evolutionary theories of senescence require understanding age-specific mortality in natural populations.
- Factors influencing mortality, both intrinsic and extrinsic, must be characterized for accurate evolutionary models.
Purpose of the Study:
- To characterize age-specific mortality and senescence in two Pacific salmon populations.
- To investigate the influence of arrival timing and extrinsic factors on senescence patterns.
- To test evolutionary predictions regarding senescence and predation in anadromous versus nonanadromous salmon.
Main Methods:
- Estimation of daily mortality rates throughout the breeding season for Pacific salmon.
- Comparison of senescence rates between early and late-arriving individuals.
- Analysis of interannual variation in senescence, considering factors like water temperature and predation.
Main Results:
- Daily mortality rates increased significantly during the breeding season, ranging from 0 to 0.2-0.5.
- Earlier-arriving salmon displayed delayed or slower senescence.
- Interannual variation in senescence was substantial, influenced by extrinsic factors like water temperature.
- Contrary to expectations, sockeye salmon (anadromous) did not exhibit faster senescence than kokanee (nonanadromous), despite higher predation.
Conclusions:
- Pacific salmon provide a valuable model for studying the evolution of senescence.
- Interannual environmental variability can mask or influence interpopulation differences in senescence.
- Further research is needed to differentiate the roles of adaptive and nonadaptive variation in senescence patterns.