Plasticity of Life History Traits in Arctic Charr: Use of Retrospective Data to Couple Migration Data with Environmental Variation

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The relationships between morphology and environmental history will be investigated. The plan of research is aimed at 1) refining and advancing promising, but nascent, techniques for extracting a record of the past life history and environmental conditions encountered by individual fish from otolith carbonate and archival tags, and 2) exploring a fresh approach to investigate the influence of environmental conditions upon morphology and life history plasticity by applying experimentally validated otolith techniques to individuals from a multitude of natural conditions. The goals are to establish retrospective and predictive relationships between the chemical structure of otoliths and environmental factors: to understand interactions among environmental factors that affect chemical structure; and to combine the environmental information encoded in otoliths with field observations to evaluate the importance of biotic and abiotic parameters to the establishment of divergent life history patterns in Arctic charr. Daily growth increments, the ratios of elements in the otolith and archival tag information will be used to back-calculate environmental and somatic changes for individual fish. Techniques will be applied to: 1) Assess life history data (i.e., growth rates, age structure, hatch date distribution, timing of spawning, etc.) in terms of life history strategies. 2) Establish the importance of critical life-history transitions, conditions affecting their onset, and derive migrational schemes (whether an individual is a migrant or a resident, age at first migration, whether a former migrant individual will resume a resident life history strategy, and the events leading and following migration) by investigating the structural and elemental composition of fish otoliths. 3) Detect differences in growth and life histories between different geographical areas as related to hydrographic, trophic or habitat conditions. 4) Precisely time the occurrence of several pivotal life history transitions and correlate them with environmental variables. The results of the proposed research will provide a paradigm to the study of fish life histories. Such knowledge is vital to our understanding of the processes fundamental to adaptable life history patterns and would make it possible to link growth and migration to environmental occurrences. This would provide insight to the ecological process of interactions between a species and its environment. In a general ecological sense such information is of great and fundamental importance since it will allow to reconstruct the complex environmental interactions that are integrated among individuals to provide for both the short term stability and the long term evolution of families of individuals, populations and species.