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.

Improving the age reading of East Greenland Atlantic cod ( Gadus morhua ) by determining otolith growth zone timing and annuli widths

2020 ◽  
Vol 27 (6) ◽  
pp. 628-632
Author(s):  
Mette Svantemann Lyngby ◽  
Frank Rigét ◽  
Anja Retzel ◽  
Rasmus Hedeholm ◽  
Peter Grønkjær
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Growth Zone ◽  
Otolith Growth ◽  
East Greenland ◽  
Age Reading

Effects of sex, stock, and environment on the shape of known-age Atlantic cod (Gadus morhua) otoliths

2004 ◽  
Vol 61 (2) ◽  
pp. 158-167 ◽  
Author(s):  
M Cardinale ◽  
P Doering-Arjes ◽  
M Kastowsky ◽  
H Mosegaard
Keyword(s):  
Shape Analysis ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fourier Descriptors ◽  
Faroe Islands ◽  
Stock Identification ◽  
Relative Importance ◽  
Age Classes ◽  
Otolith Shape ◽  
Left And Right

The effects of sex, stock, and environment on the shape of known-age Atlantic cod (Gadus morhua) otoliths from the Faroe Islands were investigated. Moreover, the feasibility of otolith shape analysis for stock identification was evaluated. The shape was described by using several normalized Fourier descriptors and morphometric variables. There were no consistent differences between the left and right otoliths and between sexes within different age classes, stocks, and environments. With our experimental design, we could evaluate the relative importance of genetic and environmental conditions (water temperature and diet regime) on otolith shape and morphometrics. Using otolith shape, cod individuals were significantly separated into Bank and Plateau stocks. Total classification success was between 79% and 85% between stocks and between 85% and 96% between environments for the different age classes. The significant differences in otolith shape between Faroe Bank and Faroe Plateau cod stocks provided a phenotypic basis for stock separation. Stock and environmental influences were substantial in determining the shape of cod otoliths.

Otolith growth and zone formation during first maturity and spawning of Atlantic cod (Gadus morhua)

2020 ◽  
Vol 77 (1) ◽  
pp. 113-123 ◽  
Author(s):  
Christian Irgens ◽  
Arild Folkvord ◽  
Håkon Otterå ◽  
Olav S. Kjesbu
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Somatic Growth ◽  
Otolith Growth ◽  
Zone Formation ◽  
Stock Biomass ◽  
Tank Experiment ◽  
The Individual ◽  
First Maturity

Specific impacts of somatic growth, sexual maturation, and spawning events on otolith zone formation in Atlantic cod (Gadus morhua) were assessed in a 33-month tank experiment, using Barents Sea cod and Norwegian coastal cod. High and low feeding ration combinations were used to mimic environmental stressors in the field. For both stocks, apparent macrostructural “spawning zones” in otoliths are registered in statutory stock monitoring programs to estimate age at maturity, thus adding key information to stock biomass assessments. We found that substantial energy investments in reproduction caused reductions in otolith growth and altered proportional width between translucent and opaque zones. These effects, however, were only statistically significant among individuals with high reproductive investments, while otoliths from individuals with low investments did not differ from the otoliths for immatures. Reproduction may thus not necessarily induce spawning zones, and alternatively, spawning zones may not necessarily reflect reproduction. Altogether, this suggests that the individual energy level, as a premise for metabolic activity, plays a key role in the formation of such zones and thus is related to environmental conditions.

scholarly journals Non-linearity in stock–recruitment relationships of Atlantic cod: insights from a multi-model approach

2019 ◽  
Vol 77 (4) ◽  
pp. 1492-1502 ◽  
Author(s):  
Camilla Sguotti ◽  
Saskia A Otto ◽  
Xochitl Cormon ◽  
Karl M Werner ◽  
Ethan Deyle ◽  
...  
Keyword(s):  
Environmental Variables ◽  
Gadus Morhua ◽  
Fishery Management ◽  
Atlantic Cod ◽  
Stock Assessment ◽  
Fish Stock ◽  
Recovery Potential ◽  
Stock Recruitment ◽  
Model Approach ◽  
Non Parametric

Abstract The stock–recruitment relationship is the basis of any stock prediction and thus fundamental for fishery management. Traditional parametric stock–recruitment models often poorly fit empirical data, nevertheless they are still the rule in fish stock assessment procedures. We here apply a multi-model approach to predict recruitment of 20 Atlantic cod (Gadus morhua) stocks as a function of adult biomass and environmental variables. We compare the traditional Ricker model with two non-parametric approaches: (i) the stochastic cusp model from catastrophe theory and (ii) multivariate simplex projections, based on attractor state-space reconstruction. We show that the performance of each model is contingent on the historical dynamics of individual stocks, and that stocks which experienced abrupt and state-dependent dynamics are best modelled using non-parametric approaches. These dynamics are pervasive in Western stocks highlighting a geographical distinction between cod stocks, which have implications for their recovery potential. Furthermore, the addition of environmental variables always improved the models’ predictive power indicating that they should be considered in stock assessment and management routines. Using our multi-model approach, we demonstrate that we should be more flexible when modelling recruitment and tailor our approaches to the dynamical properties of each individual stock.

scholarly journals Detecting regime shifts in fish stock dynamics

2015 ◽  
Vol 72 (11) ◽  
pp. 1619-1628 ◽  
Author(s):  
Tommi Perälä ◽  
Anna Kuparinen
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Stock Assessment ◽  
Detection Algorithm ◽  
Regime Shifts ◽  
Change Point Detection ◽  
Fish Stock ◽  
Fish Stocks ◽  
Data Generating Process ◽  
Change In Mean

Environmental factors such as water temperature, salinity, and the abundance of zooplankton can have major effects on certain fish stocks’ ability to produce juveniles and, thus, stock renewal ability. This variability in stock productivity manifests itself as different productivity regimes. Here, we detect productivity regime shifts by analyzing recruit-per-spawner time series with Bayesian online change point detection algorithm. The algorithm infers the time since the last regime shift (change in mean or variance or both) as well as the parameters of the data-generating process for the current regime sequentially. We demonstrate the algorithm’s performance using simulated recruitment data from an individual-based model and further apply the algorithm to stock assessment estimates for four Atlantic cod (Gadus morhua) stocks obtained from RAM legacy database. Our analysis shows that the algorithm performs well when the variability between the regimes is high enough compared with the variability within the regimes. The algorithm found several productivity regimes for all four cod stocks, and the findings suggest that the stocks are currently in low productivity regimes, which have started during the 1990s and 2000s.

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.

Advances in Fish Tagging and Marking Technology

2012 ◽  
Keyword(s):  
Large Scale ◽  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Stock Assessment ◽  
Stock Identification ◽  
Quality Of Data ◽  
Mark Recapture ◽  
International Industry ◽  
Research Initiatives

<i>Abstract</i>.—In the Gulf of Maine region, Atlantic cod <i>Gadus morhua</i>, are managed as three separate stocks: in U.S. waters, the Gulf of Maine (5Y) and Georges Bank (5Z) stocks and in Canadian waters, the Bay of Fundy stock (4X). The Northeast Regional Cod Tagging Program (NRCTP), a large-scale, international collaborative tagging program, was initiated in 2003 and provides the first region-wide, international snapshot of cod movements, mixing, and growth across all three management areas. As the 2008 stock assessment of Atlantic cod was approaching, these mark–recapture data (114,473 tag releases and >6,500 recaptures) were being analyzed for stock identification purposes. Analysis of raw and weighted data indicate exchanges between different areas which are likely related to spawning behavior, maturation, and environmental conditions. Two core assumptions when defining a stock are that (1) the stock is self-sustaining and that (2) neighboring stocks exist in isolation; the migration patterns observed in the current study may substantially violate both assumptions. With additional ongoing assessments into spatial variation in key life history characteristics of growth and natural mortality, the NRCTP exemplifies the role of conventional mark–recapture data in the complex process of stock identification. The geographic scale and quality of data collected during the NRCTP also confirm the value of international, industry-science collaborative research initiatives; involving this data in both stock assessments and future management initiatives is rewarding to the ~250 commercial and recreational fishermen who tagged cod for this program.

Sign in / Sign up

Export Citation Format

Share Document