Otolith shape differences between ecotypes of Icelandic cod (<i>Gadus morhua</i>) with known migratory behaviour inferred from data storage tags

Bardarson, Hlynur; McAdam, Bruce J.; Þorsteinsson, Vilhjálmur; Hjörleifsson, Einar; Marteinsdóttir, Guðrún

doi:10.1139/cjfas-2016-0307

Cited by 14 publications

(29 citation statements)

References 41 publications

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“…In summary, this study supports previous reports of discrimination of Icelandic cod ecotypes on the basis of otolith shape [12], but with important caveats that may limit broad applicability.…”

Section: Discussionsupporting

confidence: 89%

“…The Pan I locus genotype was used as the exclusive indicator for ecotype identity, as the AA genotype is associated with the coastal ecotype, the BB genotype is associated with the frontal ecotype, and the heterozygote AB displays both frontal and coastal behaviour [12]. This genetic information was obtained from tissue remaining on the otoliths as reported by Jakobsdóttir et al [28].…”

Section: Sampling and Measurementsmentioning

confidence: 99%

“…Two distinct ecotypes of Atlantic cod ( Gadus morhua ) have been repeatedly reported from throughout the trans-oceanic range of the species [9, 10, 11]. Off the coast of Iceland, data storage tag (DST) profiles have been used to identify a coastal ecotype and a more migratory (frontal) ecotype associated with thermal fronts [6, 12, 13]. In addition, there is evidence of fine-scale differences in spawning habitat selection between the ecotypes [6].…”

Section: Introductionmentioning

confidence: 99%

“…Although the otolith‘s shape is unique to each species, both internal and external otolith shape have been used to discriminate between stock components [18, 20, 21]. The external otolith shape has recently been used to predict the ecotype identity of cod around Iceland, with DST profiles and Pan I genotyping used to validate the results [12].…”

Section: Introductionmentioning

confidence: 99%

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

Jónsson

Sólmundsson

et al. 2021

Preprint

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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 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.

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Section: Discussionsupporting

confidence: 89%

Section: Sampling and Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Jónsson

Sólmundsson

et al. 2021

Preprint

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“…Values from 0 to 0.50 indicate Atlantic cod with intermediate to high migratory tendency, and values from 0.50 to 1 indicate cod with intermediate to high resident (coastal) tendency. This GLM has previously been selected as the best model for classification of otoliths to migratory ecotypes, correctly predicting the migratory ecotypes of Atlantic cod around Iceland in more than 90% of cases (Bardarson et al, 2017). See Supplementary Table 2 for specifics of assignment.…”

Section: Otolith Shape Analysismentioning

confidence: 99%

Change in Atlantic cod migrations and adaptability of early land-based fishers to severe climate variation in the North Atlantic

et al. 2019

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We use biochemical, biological, archaeological, and historical analysis to examine relationships between Atlantic cod migration, sea temperature, and shifts in the distribution and occupancy of historical fishing sites in Iceland during the last millennium. Results support the hypothesis that the cooling climate of the North Atlantic during the period commonly referred to as the Little Ice Age coincided with changes in Atlantic cod migration patterns. Historical analysis shows a concomitant increase in reports of worsening Atlantic cod fishing and a severe decrease in domestic fishing, particularly in north Iceland. We conclude that Atlantic cod fisheries in Iceland originally thrived because of the proximity to cod migration routes. However, despite the mobility of local fishers, fluctuations in fish migrations, coupled with a harsher climate and increased competition for fishing grounds, resulted in a stagnation that lasted until the eventual modernization of the fishery in the mid-nineteenth century.

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