Scale reading validation for estimating age from tagged fish recapture in a brown trout (Salmo trutta) population

Rifflart, Renaud; Marchand, Frédéric; Rivot, Étienne; Baglinière, Jean-Luc

doi:10.1016/j.fishres.2005.11.018

Cited by 23 publications

(18 citation statements)

References 22 publications

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“…The software Image-J v. 1.4.1 [40] was employed to digitize the position of each growth ring (circulus) and to measure inter-circuli spacing with reference to a calibrated scale bar [41]. Freshwater and marine ages were determined based on the number of annuli [42], and the point of entry of smolts into the sea identified by a change from concave to convex circuli (i.e. the point where circuli open outwards on the posterior zone of the scale) and presence of broken growth rings [43].…”

Section: Methodsmentioning

confidence: 99%

Mixed-Effects Modelling of Scale Growth Profiles Predicts the Occurrence of Early and Late Fish Migrants

et al. 2013

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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 in relation to conspecifics' performance. Unfortunately, assessing individual variation in growth rates is problematic under natural conditions because subjects typically need to be marked, repeated measurements of body size are difficult to obtain in the field, and recaptures may be limited to a few time events which will generally vary among individuals. The analysis of consecutive growth rings (circuli) found on scales and other hard structures offers an alternative to mark and recapture for examining individual growth variation in fish and other aquatic vertebrates where growth rings can be visualized, but accounting for autocorrelations and seasonal growth stanzas has proved challenging. Here we show how mixed-effects modelling 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 grew faster than late migrants during their first year of life in freshwater in two natural populations, suggesting that migration into the sea was triggered by ontogenetic (intrinsic) drivers, rather than by competition with conspecifics. Our study highlights the profound effects that early growth can have on age at migration of a paradigmatic fish migrant and illustrates how the analysis of inter-circuli spacing can be used to reconstruct the detailed growth of individuals when these cannot be marked or are only caught once.

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Section: Methodsmentioning

confidence: 99%

Mixed-Effects Modelling of Scale Growth Profiles Predicts the Occurrence of Early and Late Fish Migrants

et al. 2013

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“…The freshwater and marine ages were determined based on the number of annuli [36], and the points of entry of smolts into the sea (beginning of marine phase) and end of the first marine growing season (post-smolt growth, PSG) were noted [16]. Twenty three finnocks (individuals which had returned to freshwater before completing one full winter at sea [37]) were excluded from analysis as these provided no comparable data on post-smolt growth.…”

Section: Methodsmentioning

confidence: 99%

And the Last Shall Be First: Heterochrony and Compensatory Marine Growth in Sea Trout (Salmo trutta)

et al. 2012

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Early juvenile growth is a good indicator of growth later in life in many species because larger than average juveniles tend to have a competitive advantage. However, for migratory species the relationship between juvenile and adult growth remains obscure. We used scale analysis to reconstruct growth trajectories of migratory sea trout (Salmo trutta) from six neighbouring populations, and compared the size individuals attained in freshwater (before migration) with their subsequent growth at sea (after migration). We also calculated the coefficient of variation (CV) to examine how much body size varied across populations and life stages. Specifically, we tested the hypothesis that the CV on body size would differ between freshwater and marine environment, perhaps reflecting different trade-offs during ontogeny. Neighbouring sea trout populations differed significantly in time spent at sea and in age-adjusted size of returning adults, but not on size of seaward migration, which was surprisingly uniform and may be indicative of strong selection pressures. The CV on body size decreased significantly over time and was highest during the first 8 months of life (when juvenile mortality is highest) and lowest during the marine phase. Size attained in freshwater was negatively related to growth during the first marine growing season, suggesting the existence of compensatory growth, whereby individuals that grow poorly in freshwater are able to catch up later at sea. Analysis of 61 datasets indicates that negative or no associations between pre- and post-migratory growth are common amongst migratory salmonids. We suggest that despite a widespread selective advantage of large body size in freshwater, freshwater growth is a poor predictor of final body size amongst migratory fish because selection may favour growth heterochrony during transitions to a novel environment, and marine compensatory growth may negate any initial size advantage acquired in freshwater.

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“…In the laboratory, total egg number and average egg size (egg diameter, D) were determined for each female from a random sample of 20 eggs to nearest 0.1 mm with a digital micrometer for three times. Scales were used for estimating age (Rifflart et al 2006). All specimens were preserved in 10% formalin and kept in the Museum of Freshwater Fishes, Institute of Hydrobiology, Chinese Academy of Sciences (IHB, CAS).…”

Section: Methodsmentioning

confidence: 99%

The reproductive traits of brown trout (Salmo trutta fario L.) from the Yadong River, Tibet

Hao

Chen

2008

Environ Biol Fish

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Some key aspects of the reproductive strategy of the brown trout (Salmo trutta fario L.) in the Yadong River, Tibet, including spawning season, age at sexual maturity, fecundity and egg size, have been studied. The majority of the samples were less than 215 mm and age ranged from 1 to 4 in both sexes, indicating that the majority of the fish were younger and the pressure by overfishing was high. The spawning periodicity was determined to be between the end of October and January, mainly in November and December. The ratio of male to female brown trout population (1.29:1 with P>0.05) suggested no sex significant differences, although males were significantly more abundant than females in October (P<0.0001) on monthly basis. Age and size of males and females at maturity was different and males matured earlier than females. Fecundity was markedly correlated with their body weight (P< 0.001, r = 0.9255), standard length (P <0.01, r = 0.8879), and gonad weight (P<0.001, r=0.9366).The mean size of mature eggs in the spawning season was: 4.0±0.45 mm and tended to increase along with the female spawners size (P <0.001, r= 0.9641). Further researches about the brown trout population in the Yadong River should be conducted on issues such as artificial reproduction, culture, conservation, management, and restocking.

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Scale reading validation for estimating age from tagged fish recapture in a brown trout (Salmo trutta) population

Cited by 23 publications

References 22 publications

Mixed-Effects Modelling of Scale Growth Profiles Predicts the Occurrence of Early and Late Fish Migrants

Mixed-Effects Modelling of Scale Growth Profiles Predicts the Occurrence of Early and Late Fish Migrants

And the Last Shall Be First: Heterochrony and Compensatory Marine Growth in Sea Trout (Salmo trutta)

The reproductive traits of brown trout (Salmo trutta fario L.) from the Yadong River, Tibet

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