scholarly journals Age validation of juvenile cod in the Western Baltic Sea

2018 ◽  
Vol 76 (2) ◽  
pp. 430-441 ◽  
Author(s):  
Kate McQueen ◽  
Josef Hrabowski ◽  
Uwe Krumme
Keyword(s):  
Gadus Morhua ◽  
Age Determination ◽  
Individual Growth ◽  
Age Validation ◽  
Length Frequency ◽  
Individual Growth Rate ◽  
Peak Summer ◽  
Age Reading ◽  
Baltic Cod

Abstract The methods routinely used to estimate fish age are often un-validated and susceptible to errors and uncertainties. Despite numerous attempts, age determination of western Baltic cod (WBC, Gadus morhua) using otoliths is still unreliable, predominantly due to inconsistent interpretation of the first translucent zone (TZ). Length-frequencies of undersized (<38 cm) cod collected during 2013–2016 from pound nets near Fehmarn Island were analysed to understand TZ formation patterns. A clear minimum separated two cohorts within the length-frequency samples every year. The length-frequency information was combined with otolith edge analysis to observe the development of TZs in age-0 and age-1 cod otoliths, and to validate the timing of TZ formation, which was consistently completed between September and December. Mean TZ diameters of 4 917 juvenile cod otoliths varied between cohorts (mean diameters of the first TZ: 2.0 ± 0.5 mm; second TZ: 3.9 mm ± 0.5) and TZ diameter variation was found to be related to individual growth rate. The timing of formation of the first TZ was positively related to water temperature, and was confirmed as a “summer ring” rather than a “winter ring”. TZ formation and shallow-water occupancy suggest an influence of peak summer water temperatures on WBC ecology. An age reading guide for juvenile WBC otoliths is provided.

Why is age determination of Baltic cod (Gadus morhua) so difficult?

2010 ◽  
Vol 67 (6) ◽  
pp. 1198-1205 ◽  
Author(s):  
Karin Hüssy
Keyword(s):  
Gadus Morhua ◽  
Age Determination ◽  
Zone Formation ◽  
Frequency Distributions ◽  
Daily Increment ◽  
Reading Frequency ◽  
Traditional Age ◽  
Age Reading ◽  
Baltic Cod

Abstract Hüssy, K. 2010. Why is age determination of Baltic cod (Gadus morhua) so difficult? – ICES Journal of Marine Science, 67: 1198–1205. The aim of this study was to evaluate the consistency of three methods for assigning annuli in adult Baltic cod otoliths. The methods examined were (i) daily increment patterns, (ii) opacity profiles, and (iii) traditional age reading. Frequency distributions of the distance from the nucleus to the different zones showed that the first annulus of traditional age reading missed the first zone of both increment and opacity methods, but overlapped with the second zone identified by these methods. This pattern did not continue over subsequent zones. Frequency distributions of increment patterns were similar to opacity patterns. However, within individual fish, the co-occurrence of overlap between the two patterns was random. In cases where there was overlap, translucent zone formation started just before the disappearance of visible increments. Overlap in 1 year did not necessarily lead to a consistent pattern the following year, and overlap was not influenced by sex or fish size. The results suggest that otolith opacity in Baltic cod is not associated with seasonal patterns in daily increment structure and that traditional age determination based on otolith opacity yields highly uncertain estimates of age.

scholarly journals Bomb dating, age validation and quality control of age determinations of monodontids and other marine mammals

2014 ◽  
Vol 8 ◽  
Author(s):  
Steven E Campana ◽  
Robert EA Stewart
Keyword(s):  
Quality Control ◽  
Marine Mammals ◽  
Age Determination ◽  
Age Validation ◽  
Age Bias ◽  
Bomb Radiocarbon ◽  
Control Protocols ◽  
The 1960S ◽  
Age Determinations

Methods for confirming the accuracy of age determination methods are reasonably well established in fishes, but the millions of routine age determinations which take place every year require their own quality control protocols. In contrast, methods for ensuring accuracy in age determination of monodontids and other marine mammals are still being developed. Here we review the basis and application of bomb radiocarbon to marine mammal age validation, highlighting its value for providing unambiguous estimates of age for belugas and other long-lived animals which form growth bands. Bomb radiocarbon is particularly useful for marine mammals, given that the age of an individual animal can be determined to within ±1-3 years, as long as it was alive during the 1960s. However, ongoing age determinations require careful monitoring to ensure that age interpretations remain consistent across ages and through time. Quality control protocols using reference collections of ageing material, in conjunction with age bias plots and measures of precision, are capable of detecting virtually all of the systematic ageing errors that often occur once age determinations of an animal become routine.

scholarly journals Slave to the rhythm: seasonal signals in otolith microchemistry reveal age of eastern Baltic cod (Gadus morhua)

2015 ◽  
Vol 73 (4) ◽  
pp. 1019-1032 ◽  
Author(s):  
K. Hüssy ◽  
J. Gröger ◽  
F. Heidemann ◽  
H.-H. Hinrichsen ◽  
L. Marohn
Keyword(s):  
North Sea ◽  
Gadus Morhua ◽  
Statistical Significance ◽  
Structural Break ◽  
Age Determination ◽  
Element Concentrations ◽  
Visual Contrast ◽  
Growth Zones ◽  
Eastern Baltic ◽  
Baltic Cod

Abstract Annual growth zones in cod otoliths from the eastern Baltic stock are less discrete than in other cod stocks leading to biased age reading, which recently led to a failure of age-based assessment in the eastern Baltic cod stock. In this study, we explored the applicability of minor and trace element patterns in cod otoliths for age determination. By first identifying elements of interest in a stock without ageing problems, western Baltic cod, we then tested their applicability on another stock without ageing problems, North Sea cod, and finally applied this knowledge to estimate age of eastern Baltic cod. In western Baltic cod, matching patterns with respect to occurrence of minima and maxima in both otolith opacity and element concentrations were found for Cu, Zn, and Rb, and inverse patterns with Mg and Mn. No match was found for Pb, Ba, and Sr. In the test stock, the North Sea cod, the same patterns in Cu, Zn, Rb, Mg, and Mn signals occurred. All eastern Baltic cod with low visual contrast between growth zones exhibited clearly defined synchronous cycles in Cu, Zn, Rb and Pb. Using a combined finite differencing method and structural break models approach, the statistical significance of the local profile minima were identified, based on which their age could be estimated. Despite extensive environmental differences between the three areas examined, the element concentrations of Cu, Zn, and Rb were strongly correlated in all individuals with similar correlations in all three areas, suggesting that the incorporation mechanisms are the same for these elements and independent of environmental concentrations.

Influence of growth and survival costs of reproduction on Atlantic cod, Gadus morhua, population growth rate

1999 ◽  
Vol 56 (9) ◽  
pp. 1612-1623 ◽  
Author(s):  
Jeffrey A Hutchings
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Environmental Stochasticity ◽  
Individual Growth ◽  
Growth And Survival ◽  
Individual Growth Rate ◽  
Age Structured ◽  
Reproductive Rates

A stochastic, age-structured life history model was used to examine how age at maturity (theta), pre- (Zimm) and postreproductive (Zmat) mortality, and postreproductive growth rate can affect maximum reproductive rates of fish at low population size. Simulations suggest that annual (r) and per-generation (R0) metrics of population growth for Newfoundland's northern Grand Bank Atlantic cod, Gadus morhua, are primarily influenced by changes to mortality prior to and following reproduction. At observed weights at age and Zmat = 0.2, r ranged between 0.135 and 0.164 for cod maturing at between 4 and 7 years. Incremental increases in either Zimm or Zmat of 0.1 were associated with 0.03-0.05 reductions in r. To effect similar reductions, individual growth rate would have to decline by approximately one half. At observed weights at age, increases in Zmat from 0.20 to 0.45 increased the probability of negative per-generation growth from 3 to 26% for cod maturing at 4 years and from 6 to 46% for cod maturing at 7 years. Thus, even in the absence of fishing mortality, little or no population growth by Atlantic cod may not be unexpected in the presence of environmental stochasticity, particularly when accompanied by increases in mortality and declining individual growth.

Age and stock structure of gemfish (Rexea solandri) in New Zealand waters

1999 ◽  
Vol 50 (2) ◽  
pp. 103 ◽  
Author(s):  
P. L. Horn ◽  
R. J. Hurst
Keyword(s):  
Growth Parameters ◽  
Age Determination ◽  
Natural Mortality ◽  
Stock Structure ◽  
Von Bertalanffy ◽  
Length Frequency ◽  
Frequency Distributions ◽  
The North ◽  
Spawning Areas

Age determination of gemfish by counting hyaline zones in otoliths was validated by following the progression of modes in length–frequency distributions and the progression of strong and weak year classes in age–frequency distributions. Length–frequency and otolith samples were examined from four areas (west Northland, east Northland and Bay of Plenty, Wairarapa coast, and the Stewart- Snares shelf). Age–frequency distributions and von Bertalanffy growth parameters were calculated and compared between areas. Two gemfish stocks are indicated on the basis of patterns of year class strengths, trends in commercial landings and likely spawning areas; one off the east and north of the North Island, and another off the west and south of the South Island. Estimates of natural mortality are presented for the two stocks.

scholarly journals The effect of growth rate on otolith-based discrimination of cod (Gadus morhua) ecotypes

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0247630
Author(s):  
Einar Pétur Jónsson ◽  
Steven E. Campana ◽  
Jón Sólmundsson ◽  
Klara B. Jakobsdóttir ◽  
Hlynur Bárðarson
Keyword(s):  
Growth Rate ◽  
Gadus Morhua ◽  
Sampling Period ◽  
Individual Growth ◽  
Discrete Wavelet ◽  
Shape Variation ◽  
Otolith Shape ◽  
Individual Growth Rate ◽  
The Individual ◽  
The Relationship

Otolith shape has previously been used to identify ecotypes within the Icelandic cod (Gadus morhua) stock, using DST profiles to validate the results. Fish otolith shape variation has repeatedly been found to be largely determined by growth rate. To examine the effect of growth rate on the relationship between otolith shape and cod ecotypes (using the Pan I genotype as a proxy for ecotype), 826 archived sagittal otoliths collected over a 58 year sampling period were retrieved, the individual growth rate calculated, and otolith shape described using both Normalized Elliptic Fourier transform and Discrete Wavelet transform. Discriminant functions of otolith shape successfully classified ecotype, whether using Fourier or Wavelet descriptors, but only when excluding a heterozygous genotype from the analysis. The otolith shape variability of this genotype lowered the classification success, while otolith shape, in turn, was significantly affected by growth rate and cohort. Growth rate differences previously reported for the ecotypes were present, but were less marked than expected and indeed, growth rate variance attributable to ecotype identity was dwarfed by cohort- and location-related variance in growth. Such a strong effect of growth rate suggests that cod ecotype discrimination based on otolith shape is sensitive to both temporal and spatial variations in growth, which can mask the effect of ecotype-related growth rate differences on otolith shape.

scholarly journals Otolith-based discrimination of cod ecotypes and the effect of growth rate

2021 ◽  
Author(s):  
Einar Pétur Jónsson ◽  
Steven E. Campana ◽  
Jón Sólmundsson ◽  
Klara B. Jakobsdóttir ◽  
Hlynur Bárðarson
Keyword(s):  
Growth Rate ◽  
Gadus Morhua ◽  
Sampling Period ◽  
Individual Growth ◽  
Discrete Wavelet ◽  
Shape Variation ◽  
Otolith Shape ◽  
Individual Growth Rate ◽  
The Individual ◽  
The Relationship

AbstractOtolith shape has previously been used to identify ecotypes within the Icelandic cod (Gadus morhua) stock, using DST profiles to validate the results. Fish otolith shape variation has repeatedly been found to be largely determined by growth rate. To examine the effect of growth rate on the relationship between otolith shape and cod ecotypes (using the Pan I genotype as a proxy for ecotype), 826 archived sagittal otoliths collected over a 52 year sampling period were retrieved, the individual growth rate calculated, and otolith shape described using both Normalized Elliptic Fourier transform and Discrete Wavelet transform. Discriminant functions of otolith shape yielded high ecotype classification success, whether using Fourier or Wavelet descriptors, but only when excluding a heterozygous genotype from the analysis. The otolith shape variability of this genotype lowered the classification success, while otolith shape, in turn, was significantly affected by growth rate and cohort. Growth rate differences previously reported for the ecotypes were present, but were less marked than expected and indeed, growth rate variance attributable to ecotype identity was dwarfed by cohort- and location-related variance in growth. Such a strong effect of growth rate suggests that cod ecotype discrimination based on otolith shape is sensitive to both temporal and spatial variations in growth, which can mask the effect of ecotype-related growth rate differences on otolith shape.

Age determination of mysticete whales using 210Pb/226Ra disequilibria

2003 ◽  
Vol 81 (1) ◽  
pp. 21-32 ◽  
Author(s):  
Craig R Kastelle ◽  
Kim EW Shelden ◽  
Daniel K Kimura
Keyword(s):  
Growth Rate ◽  
Age Determination ◽  
Decay Chain ◽  
Individual Growth ◽  
Gray Whale ◽  
Gray Whales ◽  
Slow Growth Rate ◽  
Bowhead Whales ◽  
Radiometric Ages

Accurate age determination is fundamental to the study of population structure and individual growth rates of mysticete whales. Here the disequilibrium between 210Pb and 226Ra in the tympanic bullae of two mysticete whale species was investigated for use as a chronometer. Radiometric ageing depends upon accumulation of the naturally occurring radionuclide 226Ra (exclusive of other 238U decay-chain members) in the bullae and subsequent retention of its progeny 210Pb. Ages are determined from the 210Pb/226Ra activity ratio. Samples were obtained from five gray whales (Eschrichtius robustus) with lengths of 4.5 (a neonate), 7.8, 8.7, 10, and 11.5 m, and two bowhead whales (Balaena mysticetus) with lengths of 12.9 and 17.4 m. In gray whales, radiometric ages were estimated in the three largest whales. In the neonate, the 210Pb/226Ra ratio was above one and was not usable. The 7.8-m gray whale was used to determine the initial 210Pb/226Ra ratio required for age determination. We propose a theory of gray whale bullae growth starting at the fetal stage with an open system (with a 210Pb/226Ra > 1 and a fast growth rate), which transitions by 1 year old to a closed system (with a 210Pb/226Ra << 1 and a slow growth rate). In both bowhead whales, radiometric age could not be estimated because the 210Pb/226Ra ratio was above one. The excess 210Pb in these bullae samples was likely accumulated from the whales' environment via prey, or in the case of the neonate gray whale, across the placental boundary. Our results indicate that the underlying assumptions of the 210Pb/226Ra radiometric ageing method may not hold true in bowhead whales. Successful application of this method to bowhead whales is therefore doubtful.

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