The scnDNA locus Pan I reveals concurrent presence of different populations of Atlantic cod (Gadus morhua L.) within a single fjord

Sarvas, Tuula H.; Fevolden, Svein-Erik

doi:10.1016/j.fishres.2005.07.013

Cited by 38 publications

(24 citation statements)

References 25 publications

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“…There was a clear separation between cod spawning shallower and deeper than 125 m at locations south of Iceland. Offshore and inshore populations have been reported for cod off Norway (Sarvas and Fevolden, 2005), Greenland (Storr-Paulsen et al, 2004), and Newfoundland . In the present study, cod spawning at different depths south of Iceland may undergo different migration patterns.…”

Section: Discussionmentioning

confidence: 99%

“…Understanding stock structure is important when managing multi-stock commercial fisheries because different stocks may respond differently to exploitation and rebuilding. Much effort has been put into studying the stock structure of cod using methods such as otolith shape (Campana and Casselman, 1993;Cardinale et al, 2004), otolith chemistry (Campana et al, 1995), and genetics Knutsen et al, 2003;Sarvas and Fevolden, 2005).…”

Section: Introductionmentioning

confidence: 99%

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Otolith shape and temporal stability of spawning groups of Icelandic cod (Gadus morhua L.)

Jónsdóttir

Campana

Marteinsdóttir

2006

ICES Journal of Marine Science

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G. 2006. Otolith shape and temporal stability of spawning groups of Icelandic cod (Gadus morhua L.). e ICES Journal of Marine Science, 63: 1501e1512.During the past 5e10 years, studies exploring small-scale structure of cod populations have provided accumulating evidence for the existence of local populations. In Iceland, all cod have been thought to belong to a single management unit. Recent studies on genetic and life history variation have, however, indicated the existence of local populations. The main objective of this study is to explore the potential existence of local populations by use of otolith shape to discriminate between spawning groups of Icelandic cod. Otoliths were sampled from mature and spawning cod at spawning locations around Iceland in 2002 and 2003, and otolith shape was described using variables correlated with size (otolith area, length, width, perimeter, and weight) as well as shape (rectangularity, circularity, and 10 Fourier coefficients). Only standardized otolith variables were used so as to remove the effect of otolith size on the shape variables. Cod were on average larger and older south of Iceland, where ambient temperature was higher than northwest, north, and east of Iceland. Otolith shape effectively discriminated between cod north and south of Iceland, and it was also possible to discriminate among cod spawning below and above 125 m at spawning locations south of Iceland. Recent genetic and tagging studies have indicated differences between cod at these two depths. Correct classification of groups of cod at the different spawning locations ranged between 0% and 44%. Incorrectly classified cod were in most cases classified to adjacent spawning locations, and a high percentage of cod south of Iceland was classified to other southern locations and cod north of Iceland to other northern locations. The temporal stability of otolith shape was studied at seven spawning locations in two consecutive years. Otolith shape differences were greater between locations than among years within a location. The spawning groups are therefore likely to have remained separate during much of their lifetime.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Otolith shape and temporal stability of spawning groups of Icelandic cod (Gadus morhua L.)

Jónsdóttir

Campana

Marteinsdóttir

2006

ICES Journal of Marine Science

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“…Most cod are intensively farmed in net-pens in coastal areas used as habitat by local coastal cod. These wild cod populations are commonly genetically differentiated (Ruzzante et al 2000, Sarvas & Fevolden 2005 with varying life histories , Olsen et al 2008). Many of the coastal populations are presently at historically low abundances or close to endangered levels (Hutchings & Baum 2005).…”

Section: Introductionmentioning

confidence: 99%

Sperm characteristics and competitive ability in farmed and wild cod

Skjæraasen¹,

Mayer²,

Meager³

et al. 2009

Mar. Ecol. Prog. Ser.

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The development of cod aquaculture has raised concerns about its effect on wild stocks. One risk is hybridisation between escapees and wild cod, causing genetic introgression, and, potentially, fitness depressions in wild populations. The potential for hybridisation depends on escapee success in mating competition with wild fish. Cod have a complex mating system, with males likely to adopt either dominant or sub-dominant roles, the latter typically achieving reproductive success through sperm competition. Studies on salmonids indicate that domesticated males predominantly adopt sub-dominant roles. We therefore analysed sperm characteristics of wild and farmed cod Gadus morhua L. around the onset and end of the natural spawning season. Wild and farmed males were also paired in in vitro crosses to assess reproductive success in sperm competition. In the early spawning season, wild males had higher sperm velocity, percentages of motile and progressive cells, and spermatocrit. Sperm velocity was the main determinant of fertilisation success in in vitro sperm competition and, accordingly, wild males had higher reproductive success. At the end of spawning, the percentages of motile or progressive cells and spermatocrit were similar between wild and farmed males, but wild males maintained higher sperm velocity. Our results indicate that farmed males have limited reproductive success in sperm competition with wild male cod. This presumably reduces the risk of genetic introgression from escapees. We hypothesise that impaired sperm quality and lower reproductive fitness of farmed cod are due to inhibition of the full behavioural repertoire, lack of social structure under culture conditions, and/or nutritional deficiencies.

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“…While the pan ‐I allele probably has little, if any, direct influence on the morphological markers measured in this study, it has been found to be highly correlated to migratory and feeding behaviour as well as thermal‐bathymetric niche (Pampoulie et al , 2008; Árnasson et al , 2009; Grabowski et al , 2011). Numerous studies of G. morhua throughout the North Atlantic Ocean have described a depth‐related gradient in the relative abundance of the A‐allele (shallow water) to the B‐allele (deep) (Savaras & Fevoldin, 2005 a , b ; Pampoulie et al , 2008; Árnasson et al , 2009). Furthermore, in Icelandic waters, individuals homozygous for the B‐allele ( pan ‐I BB ) are most likely to exhibit a frontal behavioural pattern while those possessing the homozygous genotype for the A‐allele ( pan ‐I AA ) are most likely to exhibit a coastal behavioural pattern with heterozygous individuals present in relatively high numbers in each behavioural type, accounting for c .…”

Section: Discussionmentioning

confidence: 99%

Identification of stock components using morphological markers

McAdam

Grabowski

Marteinsdóttir

2012

Journal of Fish Biology

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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.

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The scnDNA locus Pan I reveals concurrent presence of different populations of Atlantic cod (Gadus morhua L.) within a single fjord

Cited by 38 publications

References 25 publications

Otolith shape and temporal stability of spawning groups of Icelandic cod (Gadus morhua L.)

Otolith shape and temporal stability of spawning groups of Icelandic cod (Gadus morhua L.)

Sperm characteristics and competitive ability in farmed and wild cod

Identification of stock components using morphological markers

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