Como parte de las actividades de la celebración del Año Darwin el 28 de abril pasado David A. Bauchamp(1) dio la charla titulada:
Linking Life History, Energetics, Growth, and Survival:
Examples from Ocean Ecology of Salmon
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Como parte de las actividades de la celebración del Año Darwin el 28 de abril pasado David A. Bauchamp(1) dio la charla titulada: Linking Life History, Energetics, Growth, and Survival: |
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The fitness responses related to alternative life history strategies often result from differences in behavior, timing, habitat use, feeding, growth, survival, and reproduction. These responses can all be linked and evaluated in terms of bioenergetic consequences for current and subsequent life stages, in the context of the prevailing environmental conditions. Bioenergetics modeling can provide a useful framework for evaluating the fitness consequences of feeding, growth, and survival associated with alternative strategies at various life stages, and can be used to compare the relative benefits of these alternatives in the face of changing environments. Two examples are presented for how inter-annual variation in stage-specific feeding and growth are strongly and mechanistically linked to overall ocean survival. In the first example from in the Gulf of Alaska, pink salmon Oncorhynchus gorbuscha, a species with a very simple 2-year life history pattern, exhibited 3-fold higher ocean survival during years associated with earlier more extensive dispersal, higher feeding and growth rates, and greater reliance on non-crustacean zooplankton during the peak summer growing season than during years of lower survival. By back-calculating stage-specific growth performance of juveniles compared to performance of those individuals that survived to the adult stage, we could demonstrate that growth and feeding differences during a critical period in mid-July-August set the conditions for subsequent size-selective mortality wherein only the faster growing individuals survived to become adults the following year. Similar analyses were also applied to Chinook salmon O. tschawytscha in Puget Sound, a species that exhibits much greater life history variability in terms of both use and duration of freshwater (weeks to months) and marine habitats (1-5 years). Again, overall ocean survival was strongly correlated (r2 > 0.80) to the body weight of juvenile Chinook sampled in offshore marine habitats of Puget Sound during July. This ocean survival relationship was much weaker (r2 < 0.35) for juvenile weight in September. In both the cases of pink and Chinook salmon, higher survival was strongly associated with high growth and feeding rates on particular prey assemblages, but not related to inter-annual differences in thermal regime during the critical growth period. In both examples, ocean survival over the 1-6 years of adult life was primarily determined by critical periods and sizes (sensu Beamish and Mahnken 1998) during the early marine life history of these populations. These results demonstrate the utility for linking survival and fitness mechanistically to stage-specific feeding and growth. This approach should be applicable for evaluating energetic and fitness consequences of alternative life history strategies for a wide range of species. Of particular importance to southern Patagonia would be an examination of invasive salmonids, which exhibit both anadromous and resident freshwater life history strategies. By modeling bioenergetic consequences of potential ontogenetic patterns in habitat use, we can project the geographic extent and nature of habitats that could be utilized by these species, and use this as a basis for evaluating their impacts on native species.
(1) David A. Beauchamp, U.S. Geological Survey, Washington Cooperative Fish and Wildlife Research Unit, University of Washington, School of Aquatic and Fisheries Sciences, Seattle, WA USA |