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 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.

Estimating population age structure using otolith morphometrics: a test with known-age Atlantic cod (Gadus morhua) individuals

2008 ◽  
Vol 65 (11) ◽  
pp. 2342-2350 ◽  
Author(s):  
P. Doering-Arjes ◽  
M. Cardinale ◽  
H. Mosegaard
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Stock Assessment ◽  
Otolith Growth ◽  
Otolith Shape ◽  
Traditional Age ◽  
Ageing Processes ◽  
Different Populations ◽  
Population And Environment ◽  
Age Reading

Traditional age reading is a rather subjective method that lacks true reproducibility, producing ageing error that propagates up to stock assessment. One alternative is represented by the use of otolith morphometrics as a predictor of age. An important issue with such a method is that it requires known-age fish individuals. Here we used known-age Atlantic cod ( Gadus morhua ) from the Faroe Bank and Faroe Plateau stocks. Cod populations usually show quite large variation in growth rates and otolith shape. We showed that including otolith morphometrics into ageing processes has the potential to make ageing objective, accurate, and fast. Calibration analysis indicated that a known-age sample from the same population and environment is needed to obtain robust calibration; using a sample from a different stock more than doubles the error rate, even in the case of genetically highly related populations. The intercalibration method was successful but generalization from one stock to another remains problematic. The development of an otolith growth model is needed for generalization if an operational method for different populations is required in the future.

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.

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.

Growth and Age Determination of the Pacific Edible Crab Cancer magister Dana

1961 ◽  
Vol 18 (5) ◽  
pp. 873-891 ◽  
Author(s):  
T. H. Butler
Keyword(s):  
British Columbia ◽  
Carapace Width ◽  
Age Groups ◽  
Age Determination ◽  
Cancer Magister ◽  
Larval Instars ◽  
Frequency Distributions ◽  
Queen Charlotte Islands ◽  
The Pacific

Of 2,820 early post-larval unsexed crabs collected by small-meshed trawl in two regions of the Queen Charlotte Islands, 1,175 were measured and the 1st and 2nd post-larval instars were identified as modes at 6.9 and 10.0 mm, respectively. Increments of 5 unsexed moulted crabs, carapace widths 6.80 to 9.96 mm, were from 36.3 to 46.5%. A total of 284 males, from 83 to 186 mm, moulted in crab traps, live-wells, and while at large as tagged specimens; 44 females, from 88 to 145 mm, moulted in traps. Using equations of regression of new carapace width on old width for both sexes and starting at the 2nd instar, average carapace widths were calculated for instars 3 to 15. In the width-frequency distributions of 8,145 crabs, separation of stages was sufficient for identification of age-groups. It is estimated that a year after hatching, males reach stage 5 or 6 (24.2 or 31.1 mm); after 2 years stage 11 or 12 (96.6 or 119.5 mm) is attained; after 3 years stage 13 (146.9 mm); after 4 years most males are in the 14th stage (176.2 mm) and above the British Columbia legal size of 165 mm; and generally after 5 years males are in stage 15 (207.5 mm). Growth of females is similar for 2 years, but afterwards is slower.

Use of lipofuscin for resolving cohorts of western rock lobster (Panulirus cygnus)

1998 ◽  
Vol 55 (4) ◽  
pp. 925-936 ◽  
Author(s):  
Matt Sheehy ◽  
Nicolavito Caputi ◽  
Christopher Chubb ◽  
Mark Belchier
Keyword(s):  
Accumulation Rate ◽  
Age Determination ◽  
Parameter Estimates ◽  
Population Parameter ◽  
Rock Lobster ◽  
Frequency Distributions ◽  
In The Wild ◽  
Established Relationship ◽  
Panulirus Cygnus

We evaluated lipofuscin age pigment as an approach to age determination of western rock lobster (Panulirus cygnus). Lipofuscin was measured using fluorescence image analysis of olfactory lobe sections from 184 juvenile lobsters from coastal nursery reefs at Seven Mile Beach, Western Australia. Modal analysis of a lipofuscin concentration-frequency histogram for this sample suggested the presence of additional age-classes, not apparent in conventional size-frequency distributions but expected to be present from earlier tag-recapture studies. Modal progression suggested a remarkably constant average lipofuscin accumulation rate of 0.31% by volume per year in the wild lobsters, which was supported by blind-trial measurements of lipofuscin in known-age laboratory-reared specimens. Lipofuscin-based age estimates, indicating that most juvenile lobsters are 3-5 years old immediately prior to recruitment to the fishery at 76 mm carapace length, agree with the long-established relationship between puerulus settlement and lobster catch 3-4 years later. Results indicate that the lipofuscin ageing technique will permit independent assessment of current population parameter estimates and be useful for determining sexual and regional differences in these for the western rock lobster.

Age estimation of barracouta (Thyrsites atun) off southern New Zealand

2002 ◽  
Vol 53 (8) ◽  
pp. 1169 ◽  
Author(s):  
P. L. Horn
Keyword(s):  
New Zealand ◽  
Validation Study ◽  
Age Estimation ◽  
Growth Parameters ◽  
Age Determination ◽  
Von Bertalanffy ◽  
Commercial Catch ◽  
Frequency Distributions

Age determination of barracouta (Thyrsites atun) by counting translucent zones in whole otoliths was validated by examining the number of zones in otoliths from consecutive juvenile modes and following the progression of a strong year class in age-frequency distributions. Readings from whole otoliths, rather than otolith sections, do not result in under-ageing of this species. The ageing interpretation was supported by the progression of a length mode in commercial catch samples over 5 years. The available data indicated a wide variation in year class strengths between years, a characteristic that was very useful in the validation study. Von Bertalanffy growth parameters were calculated, separately by sex, for barracouta from the Southland shelf, New Zealand. Female barracouta reach a significantly larger size than males.

scholarly journals It’s elemental, my dear Watson: validating seasonal patterns in otolith chemical chronologies

2020 ◽  
Author(s):  
Karin Hüssy ◽  
Maria Krüger-Johnsen ◽  
Tonny Bernt Thomsen ◽  
Benjamin Dominguez Heredia ◽  
Tomas Naeraa ◽  
...  
Keyword(s):  
Age Estimation ◽  
Gadus Morhua ◽  
Stock Assessment ◽  
Early Spring ◽  
Fish Stock ◽  
Late Winter ◽  
Seasonal Patterns ◽  
Traditional Age ◽  
Eastern Baltic ◽  
Baltic Cod

Accurate age data is essential for reliable fish stock assessment. Yet many stocks suffer from inconsistencies in age interpretation. A new approach to obtain age makes use of the chemical composition of otoliths. This study validates the periodicity of recurrent patterns in 25Mg, 31P, 34K, 55Mn, 63Cu, 64Zn, 66Zn, 85Rb, 88Sr, 138Ba, and 208Pb in Baltic cod (Gadus morhua) otoliths from tag-recapture and known-age samples. Otolith P concentrations showed the highest consistency in seasonality over the years, with minima co-occurring with otolith winter zones in the known-age otoliths and in late winter/early spring when water temperatures are coldest in tagged cod . The timing of minima differs between stocks, occurring around February in western Baltic cod and one month later in eastern Baltic cod; seasonal maxima are also stock-specific, occurring in August and October, respectively. The amplitude in P is larger in faster-growing western compared to eastern Baltic cod. Seasonal patterns with minima in winter/late spring were also evident in Mg and Mn, but less consistent over time and fish size than P. Chronological patterns in P, and to a lesser extent Mg and Mn, may have the potential to supplement traditional age estimation or to guide the visual identification of translucent and opaque otolith patterns used in traditional age estimation

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