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Mixed-effects modelling of scale growth profiles predicts the occurrence of early and late fish migrants / Francisco Marco-Rius; Pablo Caballero; Paloma Morán; Carlos Garcia De Leaniz
PLOS ONE, Volume: 8, Issue: 4
Swansea University Author: Carlos, Garcia De Leaniz
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DOI (Published version): 10.1371/journal.pone.0061744
Fish growth is commonly used as a proxy for fitness but this is only valid if individual growth variation can be interpreted inrelation to conspecifics’ performance. Unfortunately, assessing individual variation in growth rates is problematic undernatural conditions because subjects typically need t...
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Fish growth is commonly used as a proxy for fitness but this is only valid if individual growth variation can be interpreted inrelation to conspecifics’ performance. Unfortunately, assessing individual variation in growth rates is problematic undernatural conditions because subjects typically need to be marked, repeated measurements of body size are difficult to obtainin the field, and recaptures may be limited to a few time events which will generally vary among individuals. The analysis ofconsecutive growth rings (circuli) found on scales and other hard structures offers an alternative to mark and recapture forexamining individual growth variation in fish and other aquatic vertebrates where growth rings can be visualized, butaccounting for autocorrelations and seasonal growth stanzas has proved challenging. Here we show how mixed-effectsmodelling of scale growth increments (inter-circuli spacing) can be used to reconstruct the growth trajectories of sea trout(Salmo trutta) and correctly classify 89% of individuals into early or late seaward migrants (smolts). Early migrants grewfaster than late migrants during their first year of life in freshwater in two natural populations, suggesting that migrationinto the sea was triggered by ontogenetic (intrinsic) drivers, rather than by competition with conspecifics. Our studyhighlights the profound effects that early growth can have on age at migration of a paradigmatic fish migrant and illustrateshow the analysis of inter-circuli spacing can be used to reconstruct the detailed growth of individuals when these cannot bemarked or are only caught once.
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