Graphical and Statistical Methods for Determining the Consistency of Age Determinations

Campana, Steven E.; Annand, M. Christina; McMillan, James I.

doi:10.1577/1548-8659(1995)124<0131:gasmfd>2.3.co;2

Cited by 438 publications

(364 citation statements)

References 8 publications

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“…Quality control was maintained by the readers recounting earlier samples prior to initiating each reading and crosschecking the readings. The consistency of age estimates between ageing rounds and readers was assessed using age bias plots and chi-square tests of symmetry (McNemar 1947;Bowker 1948;Campana et al 1995;Hoenig et al 1995;Evans and Hoenig 1998). To resolve discrepancies between readers greater than 2 years, a consensus was reached by reading the centra together.…”

Section: Age Determinationmentioning

confidence: 99%

Validated age and growth estimates for Carcharhinus obscurus in the northwestern Atlantic Ocean, with pre- and post management growth comparisons

Natanson

Gervelis

Winton³

et al. 2013

Environ Biol Fish

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Age and growth estimates for the dusky shark, Carcharhinus obscurus, were derived from vertebral centra collected in the northwestern Atlantic Ocean. Sample collection spanned the years prior to and following the implementation of management measures . Growth was compared pre-and post-population depletion and pre-and post-management to investigate the possibility of density-mediated shifts in age and growth parameters over time. There was no evidence of difference between periods for either sex. Additionally, bomb radiocarbon dating was used to determine the periodicity of band pair formation. Results support the traditional interpretation of annual band pairs up to approximately 11 years of age. After this time, vertebral counts considerably underestimate true age. Maximum validated ages were estimated to be between 38 and 42 years of age (an increase of 15 to 19 years over the band count estimates), confirming longevity to at least 42 years of age. Growth curves estimated using only validated data were compared to those generated using band pair counts. Logistic growth parameters derived from validated vertebral length-at-age data were L ∞ = 261.5 cm FL, L o =85.5 cm, t o =4.89 year and g= 0.15 year −1 for the sexes combined. Revised estimates of age at maturity were 17.4 years for males and 17.6 years for females.

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Section: Age Determinationmentioning

confidence: 99%

Validated age and growth estimates for Carcharhinus obscurus in the northwestern Atlantic Ocean, with pre- and post management growth comparisons

Natanson

Gervelis

Winton³

et al. 2013

Environ Biol Fish

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show abstract

“…Bias and precision of annulus counts were analysed by statistical and graphical methods for each pair of replicate counts from the three interpreters. Accordingly, an age bias plot (Campana et al, 1995) was generated and a test of symmetry (Hoenig et al, 1995) computed from the corresponding age-agreement table. In this table, the main diagonal represents the frequency of fish for which the same estimated age is obtained by any combination of two interpreters, whereas each cell off the main diagonal represents a difference in estimated age between the interpreters.…”

Section: > Data Analysismentioning

confidence: 99%

Age and growth of European barbelBarbus barbus(Cyprinidae) in the small, mesotrophic River Lee and relative to other populations in England

Vilizzi

Copp

Britton

2013

Knowl. Managt. Aquatic Ecosyst.

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Key-words:habitat, conservation, scale ageing, recruitment Suspected of being in decline, the European barbel Barbus barbus population of the River Lee, a heavily-modified river in South East England, has been the subject of investigations to identify factors associated with perceived population decreases. Population surveys between 1995 and 1999 captured a total of 912 individuals, and standard length (SL) frequency analyses between years suggested that the population decline was not related to juvenile recruitment but rather to a recruitment bottleneck in fish 300-340 mm SL. This bottleneck probably results from insufficient available habitat suitable to this size class. Of the sampled fish, scales were removed from 764 and were used in a scale ageing exercise among three researchers. Analyses of their independent age estimates revealed variable interpretations, which arose from uncertainties relating to the difficulty of analysing scale patterns from relatively large, slow-growing fish. Nevertheless, error was within published acceptable margins, and age estimates revealed B. barbus in the river to age 10 years, lower than in many UK rivers. The SL-at-age growth curve was characterised by very fast growth in the initial years of life. Thus, the causal factors in the decline of this B. barbus population appear to have been in the adult life-stage habitat and were likely related to the loss of longitudinal connectivity, mainly due to the presence of water retention structures. River and aquatic ecosystem remediation strategies should therefore focus on enhancing longitudinal connectivity in conjunction with the ongoing improvement of water quality and ecosystem integrity. Mots-clés :habitat, conservation, scalimétrie, recrutement Soupçonnée d'être en déclin, la population de barbeau européen Barbus barbus de la rivière Lee, une rivière fortement modifiée dans le Sud Est de l'Angleterre, a fait l'objet d'investigations pour identifier les facteurs associés à la diminution ressentie de la population. Le suivi de population entre 1995 et 1999 a permis la capture de 912 poissons, et l'analyse des fréquences de longueur standard (SL) entre années suggère que le déclin de la population n'était pas lié au recrutement des juvéniles, mais plutôt à un goulot d'étranglement du recrutement chez les poissons de 300-340 mm SL. Ce goulot d'étranglement résulte probablement d'une insuffisance de l'habitat disponible approprié pour cette classe de taille.

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“…May the first was considered as the birth date to assign individual age to age groups. The index of the coefficient of variation (CV) [5,48] was calculated to assess the level of precision of age interpretations. Systematic differences in estimated age (bias) within readings were assessed by age bias plot.…”

Section: Age Estimate and Growthmentioning

confidence: 99%

Life history traits and implications for conservation of rock carp Procypris rabaudi Tchang, an endemic fish in the upper Yangtze River, China

et al. 2015

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Graphical and Statistical Methods for Determining the Consistency of Age Determinations

Cited by 438 publications

References 8 publications

Validated age and growth estimates for Carcharhinus obscurus in the northwestern Atlantic Ocean, with pre- and post management growth comparisons

Validated age and growth estimates for Carcharhinus obscurus in the northwestern Atlantic Ocean, with pre- and post management growth comparisons

Age and growth of European barbelBarbus barbus(Cyprinidae) in the small, mesotrophic River Lee and relative to other populations in England

Life history traits and implications for conservation of rock carp Procypris rabaudi Tchang, an endemic fish in the upper Yangtze River, China

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