Identification of stock components using morphological markers

Abstract

This study investigated the development of a quantitative method for distinguishing stock components of Icelandic cod Gadus morhua based on visual examination of morphology. The stock is known to be structured into genetically distinct geographic components (north and south of Iceland) and behavioural types that spawn sympatrically. Differences in morphology were tested between locations, genotypes (a proxy for behaviour) and sexes. Results show morphological markers on the head, fins and body of G. morhua that are correlated with the sex, genotype of the fish at the pantophysin (pan-I) locus and the location at which the fish were caught. Females were found to have relatively deep bodies, and the pan-I(BB) genotype (associated with deep-water feeding behaviour) have greater gaps between their fins. Overall, morphology is more useful for distinguishing sympatric genotypes but less powerful at identifying genetically distinct geographic sub-populations, perhaps because counter-gradient evolution reduces phenotypic differences even with an underlying genetic cause.

Living apart together: Long-term coexistence of Baltic cod stocks associated with depth-specific habitat use

“…EBC have narrower otoliths [ 23 , 29 ] and a more streamlined body shape [ 62 , 63 ], which may be attributed to the differences in the foraging and movement behaviour of the cod stocks. Other studies showed similar adaptations on otolith and body morphology in migratory cod [ 22 , 64 , 65 ], suggesting that a more streamlined otolith and body shape is advantageous for foraging in deeper waters and more active swimming behaviour.…”

Managing a Marine Stock Portfolio: Stock Identification, Structure, and Management of 25 Fishery Species along the Atlantic Coast of the United States

“…In response to the increasing demands for identifying stock units, development of pertinent methods has steadily progressed (Cadrin et al , 2014a. Traditional methods, such as the use of life history parameters, morphometrics, or parasites as natural markers, are still part of the toolbox (Baldwin et al 2012;McAdam et al 2012;Zischke et al 2013;Cadrin et al 2014a). New technologies, such as otolith microchemistry, single-nucleotide polymorphisms, or electronic tags, have greatly expanded the toolbox (Hodgins- Davis et al 2007;Rooker et al 2007;Walther et al 2008;Cadrin et al 2014a).…”

Morphological divergence in Indian oil sardine, Sardinella longiceps Valenciennes, 1847- Does it imply adaptive variation?

“…Morphological differences have been reported in many marine pelagic species, especially in clupeids (Thomas et al., ). In Atlantic cod Gadus morhua , morphological differences were associated with behavioural and ecological differentiation (McAdam et al., ). The two behavioural types, coastal and frontal, were associated with distinct morphological characteristics such as gape of mouth, eye position and spaces between fins and depth of body.…”