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.

Stock Discrimination Using Otolith Shape Analysis

1993 ◽  
Vol 50 (5) ◽  
pp. 1062-1083 ◽  
Author(s):  
Steven E. Campana ◽  
John M. Casselman
Keyword(s):  
Growth Rate ◽  
Shape Analysis ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Otolith Shape ◽  
Otolith Shape Analysis ◽  
Stock Discrimination ◽  
The Difference ◽  
Highly Correlated ◽  
Species Specific

Otolith shape has long been known to be species specific, but recent reports have pointed to its value as an indicator of stock identity. To test this hypothesis, all three pairs of otoliths were sampled from 2349 Atlantic cod (Gadus morhua) collected on spawning grounds throughout the northwest Atlantic. Otolith shape was determined with Fourier analysis and combined with measures of otolith area and perimeter. There were highly significant differences in otolith shape among most of the cod samples, but shape also differed among ages, sexes, and year-classes. The sagittal otoliths (largest pair) provided slightly better stock discrimination than did the lapillar or asteriscal otoliths. The first discriminant function was highly correlated with both fish and otolith growth rate, indicating that stock discrimination improved as the difference in stock-specific growth rate increased. Reevaluation of published studies on other species indicated that growth rate contributes more variation to regional differences in otolith shape than does stock origin. Differences in otolith shape among ages, sexes, and year-classes were also attributable to growth rate differences. To the extent that growth rates vary more between than within stocks, otolith shape analysis can provide an easily determined measure of stock identity.

scholarly journals Combined methods of otolith shape analysis improve identification of spawning areas of Atlantic cod

2006 ◽  
Vol 63 (9) ◽  
pp. 1710-1717 ◽  
Author(s):  
Elizabeth A. Galley ◽  
Peter J. Wright ◽  
Fiona M. Gibb
Keyword(s):  
Discriminant Analysis ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Irish Sea ◽  
Fourier Descriptors ◽  
Otolith Shape ◽  
Spawning Areas ◽  
Moray Firth ◽  
Combination Of Methods ◽  
Randomization Analysis

Abstract The effectiveness of otolith shape for identifying Atlantic cod (Gadus morhua) spawning populations in the northern North Sea and west coast of Scotland was investigated. Otolith shape was described using Cartesian Fourier analysis of the otolith outline and morphometric variable rectangularity. Pairwise randomization analysis of Fourier descriptors, and discriminant analysis of rectangularity and Fourier descriptors were used to identify differences between spawning stocks. Significant differences and a high classification success (>70%) in otolith shape indicated that spawning groups from Viking Bank and Moray Firth had different shapes from those of cod in other spawning areas. Significant differences in otolith shape of age 2 cod suggested that otoliths from the South Minch and Irish Sea were different from those from the Moray Firth and the Clyde. These results appear consistent with genetic evidence for a low gene flow, and tag-recapture evidence of resident populations. The results of pairwise randomization analysis and discriminant analysis differed slightly, indicating that use of a combination of methods increases the potential to identify spawning groups on the basis of otolith shape.

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.

Depth-dependent vertebral number of Atlantic cod (Gadus morhua) on the Magdalen Shallows and Scotian Shelf: stock mixing or microgeographic trends within populations?

2000 ◽  
Vol 57 (12) ◽  
pp. 2393-2401 ◽  
Author(s):  
D P Swain ◽  
K T Frank
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Spatial Scales ◽  
Relative Length ◽  
Scotian Shelf ◽  
Age Classes ◽  
Vertebral Number ◽  
Size At Age ◽  
Stock Mixing ◽  
Summer Feeding

We examined spatial variation in the vertebral number of Atlantic cod (Gadus morhua) during the summer feeding season in the southern Gulf of St. Lawrence and on the Scotian Shelf. Mean vertebral number increased significantly with depth in the southern Gulf and on the northeastern Scotian Shelf but not on the southwestern Scotian Shelf. In the southern Gulf, where sampling was most extensive, mean vertebral number increased steadily as depth increased from 25 m to over 175 m. Mean vertebral number was also strongly related to relative length within age-classes, with the larger fish at age having more vertebrae. However, the association between vertebral number and depth could not be attributed to confounding between depth and size at age. These results indicate either unexpected mixing between neighbouring cod populations or unexpected structure at fine spatial scales within cod populations.

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.

Gear-independent patterns of variation in catch of juvenile Atlantic cod (Gadus morhua) in coastal habitats

1998 ◽  
Vol 55 (6) ◽  
pp. 1430-1442 ◽  
Author(s):  
David A Methven ◽  
David C Schneider
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Cohort Size ◽  
Spatial And Temporal Patterns ◽  
Age Classes ◽  
Coastal Habitats ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Depth Gradients ◽  
Spatial Depth

Habitat and size of juvenile Atlantic cod (Gadus morhua) change substantially during the first 3 years after settlement, and hence, cohort size cannot be followed using a single gear. We investigated whether catch could be calibrated across gear types by deploying pairs of gears repeatedly in the same habitat. As expected, size selectivity differed substantially among gears. Trawls and seines generally collected individuals <200 mm. Gillnets and jiggers collected individuals >150 mm. Size modes, corresponding to age-classes, were common to catches of most gears. Highest catches were taken by trawls and seines. Gillnet catches were orders of magnitude lower. Standardized catches could not be calibrated across pairs of gears deployed in the same habitat at approximately the same time. However, it was possible to identify spatial depth gradients and diel changes in catch that were independent of gear. Consistent spatial and temporal patterns across gears were interpreted as characteristic of fish populations, not just of gears. Density in coastal habitats was higher at night and was higher at 4-7 m than at greater depths. These results, in conjunction with other studies, establish that coastal depths of 4-7 m represent the centre, and not the edge, of the distribution of age 0 cod in Newfoundland during autumn. Hence nursery areas during the early 1990s, a time of historically low spawning stock biomass, must be identified as the coastal zone, not offshore.

scholarly journals Análisis de la forma de los otolitos como herramienta para la discriminación de la población del stock ( Haemulon Plumieri ) blanco en la costa norte de la Península de Yucatán, México

2012 ◽  
Vol 3 ◽  
pp. 157 ◽  
Author(s):  
Christina Treinen-Crespo ◽  
Harold Villegas-Hernández ◽  
Sergio Guillén-Hernández ◽  
Miguel Ángel Ruiz-Zárate ◽  
Carlos González-Salas
Keyword(s):  
Population Structure ◽  
Shape Analysis ◽  
Yucatan Peninsula ◽  
Pairwise Comparisons ◽  
Fourier Descriptors ◽  
Northern Coast ◽  
Otolith Shape ◽  
Structured Population ◽  
Yucatán Peninsula ◽  
Elliptic Fourier Descriptors

In this study, the population structure of the white grunt (Haemulon plumieri) from the northern coast of the Yucatan Peninsula was determined through an otolith shape analysis based on the samples collected in three locations: Celestún (N 20°49’,W 90°25’), Dzilam (N 21°23’, W 88°54’) and Cancún (N 21°21’,W 86°52’). The otolith outline was based on the elliptic Fourier descriptors, which indicated that the H. plumieri population in the northern coast of the Yucatan Peninsula is composed of three geographically delimited units (Celestún, Dzilam, and Cancún). Significant differences were observed in mean otolith shapes among all samples (PERMANOVA; F2, 99 = 11.20, P = 0.0002), and the subsequent pairwise comparisons showed that all samples were significantly differently from each other. Samples do not belong to a unique white grunt population, and results suggest that they might represent a structured population along the northern coast of the Yucatan Peninsula. En este estudio, la estructura de la población del ronco blanco (Haemulon plumieri) de la costa norte de la Península de Yucatán fue determinada a través del análisis de la forma del otolito, sobre la base de las muestras recolectadas en tres localidades: Celestún (N 20°49’, W 90°25’), Dzilam (N 21°23’, W 88°54’) y Cancún (N 21° 21’, O 86° 52’). El análisis del contorno de los otolitos se basó en los descriptores elípticos de Fourier, cuyo enfoque indicó que la población de H. plumieri en la costa norte de la Península de Yucatán se compone al menos de tres unidades delimitadas geográficamente (Celestún, Dzilam y Cancún). Se observaron diferencias significativas en la forma del otolito entre todas las muestras (PERMANOVA, F2, 99 = 11.20, P = 0.0002) y las comparaciones por pares posteriores indicaron que todas las muestras fueron significativamente diferentes una de otra. Al parecer, las muestras no pertenecen a una única población, y los resultados sugieren que podría representar una población bien estructurada a lo largo de la costa norte de la Península de Yucatán.

scholarly journals Directional bilateral asymmetry in otolith morphology may affect fish stock discrimination based on otolith shape analysis

2018 ◽  
Vol 76 (1) ◽  
pp. 232-243 ◽  
Author(s):  
Kélig Mahé ◽  
Djamila Ider ◽  
Andrea Massaro ◽  
Oussama Hamed ◽  
Alba Jurado-Ruzafa ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Shape Analysis ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Fish Stock ◽  
Stock Identification ◽  
Bilateral Asymmetry ◽  
Otolith Shape ◽  
Otolith Shape Analysis ◽  
Western Mediterranean Sea

Abstract Otolith shape analysis is an efficient fish stock identification tool. However, most applications used left and right otoliths or only one of them arbitrarily chosen without testing for biases resulting from potential directional bilateral asymmetry (DA) in otolith shape, i.e. a unimodal population-level deviation form bilateral symmetry between right and left otolith shapes. In this study, 560 bogues (Boops boops) were sampled from 11 geographical locations from the Canary Islands to the Aegean Sea and elliptical Fourier descriptors were used to describe their otoliths’ shape. First, a significant otolith DA was observed at the global scale with an average amplitude of 2.77%. However, at the scale of sampling locations, DA was not always significant and varied in amplitude and direction. Second, population structure was investigated using the shape of either right otoliths or left otoliths or both together. Analyses based on right otoliths or both otoliths together, suggested three stock units: a North-Western Mediterranean Sea stock, an Eastern Mediterranean Sea stock, and a Central-Eastern Atlantic Ocean and South-Western Mediterranean Sea stock. In contrast, no coherent geographical pattern was found based on left otoliths. Our results highlight the importance of accounting for potential otolith DA in otolith shape-based stock identification.

Fishing power increases from technological development in the Faroe Islands longline fishery

2011 ◽  
Vol 68 (11) ◽  
pp. 1970-1982 ◽  
Author(s):  
Ole Ritzau Eigaard ◽  
Bjarti Thomsen ◽  
Holger Hovgaard ◽  
Anders Nielsen ◽  
Adriaan D. Rijnsdorp
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Technological Development ◽  
Melanogrammus Aeglefinus ◽  
Faroe Islands ◽  
Longline Fishery ◽  
Catch Per Unit Effort ◽  
Total Allowable Catch ◽  
Input Control ◽  
Generalized Linear Modelling

During an effort-regulated period from 1996 to 2002, unregistered annual increases of 0.3% of hooks fished per day were demonstrated for the Faroe Islands longline fishery. However, annual increases were higher (1.5%) during a preceding total allowable catch regulated period, thereby invalidating an expectation of the 1996 shift in regulations (output to input control) to have induced increases in the number of hooks set per day. Underlying this result is a substantial increase in total yearly effort (fishing days) and a shift in targeting behaviour from secondary to primary (high value) target species in response to the transition from output to input control. Interview data on technology were combined with logbook data and analysed with generalized linear modelling to demonstrate haddock ( Melanogrammus aeglefinus ) and Atlantic cod ( Gadus morhua ) catch-per-unit-effort increases of 51% and 26%, respectively, following the introduction of skewed hooks and swivel line. The technological introductions were not correlated to regulation shifts. So, rather than the management system in force, an ongoing technological development seems to be the principal driver of fishing power trends. The results highlight the need to explicitly address technological development and targeting behaviour when attempting to meet conservation objectives through input control of fisheries.

Diet of harp seals (Phoca groenlandica) in nearshore waters of the northwest Atlantic during 1990 – 1993

1995 ◽  
Vol 73 (10) ◽  
pp. 1805-1818 ◽  
Author(s):  
John W. Lawson ◽  
Garry B. Stenson ◽  
Dave G. McKinnon
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Stomach Contents ◽  
Clupea Harengus ◽  
Relative Importance ◽  
Northwest Atlantic ◽  
Arctic Cod ◽  
Diet Diversity ◽  
Phoca Groenlandica ◽  
Capelin Mallotus Villosus

The nearshore diet of northwest Atlantic harp seals (Phoca groenlandica) was determined by reconstructing the contents of 1167 prey-containing stomachs (78.3% of 1490) collected from 1990 to 1993. Although harp seals consumed at least 62 species, 6 accounted for most of the mass consumed and their relative importance varied by area. Based on percent wet mass, sculpins (Cottidae) and Arctic cod (Boreogadus saida) were the main components of the diet of older seals (> 1 year old) off Labrador, whereas Arctic cod and Atlantic herring (Clupea harengus) were the main prey of seals from northeastern Newfoundland. A more diverse diet was observed in seals taken off the west coast of Newfoundland, where capelin (Mallotus villosus), herring, Atlantic cod (Gadus morhua), redfish (Sebastes spp.), and Arctic cod were the main species. Redfish and Atlantic cod were important to seals along the south coast of Newfoundland. Eighty percent of fish consumed were less than 18 cm long, smaller than those taken by commercial fisheries. Pups (less than 1 year old) consumed fewer and smaller prey of a less varied assortment. Annual and seasonal variation in the diets was observed in the collection from northeastern Newfoundland. Arctic cod was the major prey consumed throughout the year by seals of all ages, although the relative importance of herring, capelin, and squid (Teuthoidea) increased during the summer. Invertebrates and capelin made up a greater proportion of the diet in 1992, owing to a decline in consumption of Arctic cod. This finding was associated with a decrease in the mass of stomach contents. Diet diversity did not change significantly over the study period.

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