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Identification of stock components using morphological markers
B J McAdam1, T B Grabowski, G Marteinsdóttir
1Institute of Biology, University of Iceland, Sturlugata 7, Reykjavik 101, Iceland.
Journal of Fish Biology
|October 2, 2012
Summary
Morphological traits in Icelandic cod (Gadus morhua) can help distinguish between fish of different sexes and behaviors. However, these visual markers are less effective at differentiating geographically distinct populations.
Area of Science:
- Marine Biology
- Fisheries Science
- Quantitative Morphology
Background:
- Icelandic cod (Gadus morhua) populations exhibit genetic structure, with distinct northern and southern components.
- Sympatric spawning occurs between different behavioral types within Icelandic cod populations.
- Understanding stock structure is crucial for effective fisheries management and conservation.
Purpose of the Study:
- To develop a quantitative method for distinguishing Icelandic cod stock components using morphology.
- To investigate correlations between morphological traits, geographic location, genotype, and sex.
- To assess the utility of morphology in differentiating sympatric genotypes versus geographic sub-populations.
Main Methods:
- Quantitative analysis of morphological markers on the head, fins, and body of Gadus morhua.
- Testing for differences in morphology based on geographic location (north vs. south Iceland).
- Examining morphological variations related to genotype at the pantophysin (pan-I) locus (a proxy for behavior) and sex.
Main Results:
- Morphological markers on the head, fins, and body were found to be correlated with sex, genotype, and capture location.
- Females exhibited relatively deeper body morphology.
- The pan-I(BB) genotype, linked to deep-water feeding, was associated with greater gaps between fins.
Conclusions:
- Morphological traits are more effective for distinguishing sympatric cod genotypes than genetically distinct geographic sub-populations.
- Counter-gradient evolution may reduce phenotypic differences, limiting the power of morphology for geographic stock identification.
- Quantitative morphology offers insights into the complex structure of Icelandic cod populations.
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