scholarly journals Microgeographical population structure and adaptation in Atlantic cod Gadus morhua: spatio-temporal insights from gene-associated DNA markers

2011 ◽  
Vol 436 ◽  
pp. 231-243 ◽  
Author(s):  
NA Poulsen ◽  
J Hemmer-Hansen ◽  
V Loeschcke ◽  
GR Carvalho ◽  
EE Nielsen
Keyword(s):  
Population Structure ◽  
Dna Markers ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Spatio Temporal

scholarly journals Genetic population structure and gene flow in the Atlantic cod Gadus morhua: a comparison of allozyme and nuclear RFLP loci.

Genetics ◽  
1995 ◽  
Vol 139 (1) ◽  
pp. 375-385 ◽  
Author(s):  
G H Pogson ◽  
K A Mesa ◽  
R G Boutilier
Keyword(s):  
Population Structure ◽  
Gene Flow ◽  
Dna Markers ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Isolation By Distance ◽  
Frequency Variation ◽  
Cdna Clones ◽  
Genetic Population ◽  
Allozyme Loci

Abstract High levels of gene flow have been implicated in producing uniform patterns of allozyme variation among populations of many marine fish species. We have examined whether gene flow is responsible for the limited population structure in the Atlantic cod, Gadus morhua L., by comparing the previously published patterns of variation at 10 allozyme loci to 17 nuclear restriction fragment length polymorphism (RFLP) loci scored by 11 anonymous cDNA clones. Unlike the allozyme loci, highly significant differences were observed among all populations at the DNA markers in a pattern consistent with an isolation-by-distance model of population structure. The magnitude of allele frequency variation at the nuclear RFLP loci significantly exceeded that observed at the protein loci (chi 2 = 24.6, d.f. = 5, P < 0.001). Estimates of gene flow from the private alleles method were similar for the allozymes and nuclear RFLPs. From the infinite island model, however, estimates of gene flow from the DNA markers were fivefold lower than indicated by the proteins. The discrepancy between gene flow estimates, combined with the observation of a large excess of rare RFLP alleles, suggests that the Atlantic cod has undergone a recent expansion in population size and that populations are significantly displaced from equilibrium. Because gene flow is a process that affects all loci equally, the heterogeneity observed among populations at the DNA level eliminates gene flow as the explanation for the homogeneous allozyme patterns. Our results suggest that a recent origin of cod populations has acted to constrain the extent of population differentiation observed at weakly polymorphic loci and implicate a role for selection in affecting the distribution of protein variation among natural populations in this species.

Formation of the Population Structure of the Atlantic Cod Gadus morhua Linnaeus, 1758 in the Quaternary Period

2019 ◽  
Vol 45 (1) ◽  
pp. 15-21
Author(s):  
A. N. Stroganov ◽  
A. M. Orlov ◽  
A. V. Semenova ◽  
S. Yu. Orlova
Keyword(s):  
Population Structure ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Quaternary Period

scholarly journals Stock identification of Atlantic cod (Gadus morhua) in US waters: an interdisciplinary approach

2014 ◽  
Vol 71 (6) ◽  
pp. 1490-1506 ◽  
Author(s):  
Douglas R. Zemeckis ◽  
David Martins ◽  
Lisa A. Kerr ◽  
Steven X. Cadrin
Keyword(s):  
Population Structure ◽  
Gadus Morhua ◽  
Management Practices ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Biological Information ◽  
Composition Analysis ◽  
Georges Bank ◽  
Biological Population ◽  
Bank Stock

Abstract Mismatches between biological population structure and management unit boundaries often violate the unit-stock assumption, which can reduce the accuracy and relevance of stock assessment results and lead to ineffective fishery management. Since 1972, Atlantic cod (Gadus morhua) have been managed in US waters as two units: the Gulf of Maine and the Georges Bank stocks, both of which have experienced recent difficulties in rebuilding. An interdisciplinary review of available biological information was conducted to investigate cod population structure in US waters and to evaluate the biological appropriateness of the current two-stock model. Our review demonstrates that spawning components in the Great South Channel, Nantucket Shoals, southern New England, and Middle Atlantic are more connected with spawning components in the Gulf of Maine than on eastern Georges Bank, with which they are currently managed. Therefore, a modification of current stock boundaries is recommended to provide a more accurate representation of biological population structure. Proposed alternatives divide inshore and offshore spawning components into separate management units, thereby separating the current Georges Bank stock longitudinally. Continued research, including stock composition analysis, is required to evaluate uncertainties, delineate biological stocks, and develop sustainable management practices that account for intrastock diversity (e.g. winter and spring-spawning components that overlap spatially).

scholarly journals Seasonal dynamics of growth and mortality suggest contrasting population structure and ecology for cod, pollack, and saithe in a Norwegian fjord

2012 ◽  
Vol 69 (4) ◽  
pp. 537-546 ◽  
Author(s):  
Mikko Heino ◽  
Terje Svåsand ◽  
Jarle Tryti Nordeide ◽  
Håkon Otterå
Keyword(s):  
Population Structure ◽  
Seasonal Dynamics ◽  
Seasonal Changes ◽  
Gadus Morhua ◽  
Depth Distribution ◽  
Atlantic Cod ◽  
Regular Growth ◽  
Independent Unit ◽  
Norwegian Fjord ◽  
Autumn And Winter

Abstract Heino, M., Svåsand, T., Nordeide, J. T., Otterå, H. 2012. Seasonal dynamics of growth and mortality suggest contrasting population structure and ecology for cod, pollack, and saithe in a Norwegian fjord. – ICES Journal of Marine Science, 69: 537–546. We study the dynamics of Atlantic cod (Gadus morhua L.), pollack (Pollachius pollachius L.), and saithe (Pollachius virens L.) in Masfjorden, a small fjord in western Norway. Annually, cohorts of pollack and cod grow in size and decline in abundance, as expected of closed populations, whereas saithe virtually disappear before maturity. Seasonally, in contrast, the dynamics of cod and pollack differ. Pollack shows a regular growth pattern, with most of the growth taking place in summer. Its abundance-at-age shows strong seasonal variations, with a marked increase from spring to summer followed by a decline through autumn and winter. These patterns relate partly to seasonal changes in depth distribution and catchability. Combined with the observation that spawning-stage pollack are abundant in spring, we interpret these patterns to suggest that pollack in Masfjorden represent a dynamically independent unit. Seasonal changes in abundance are less marked for cod, and seasonal changes in depth distribution seem insignificant. However, cod shows an unusual pattern in length at age, with no apparent growth in summer and fast growth in autumn. These patterns suggest that the population structure of cod may be more open than that of pollack and may involve mixing of more than one population component.

scholarly journals Spawning site fidelity by Atlantic cod (Gadus morhua) in the Gulf of Maine: implications for population structure and rebuilding

2014 ◽  
Vol 71 (6) ◽  
pp. 1356-1365 ◽  
Author(s):  
Douglas R. Zemeckis ◽  
William S. Hoffman ◽  
Micah J. Dean ◽  
Michael P. Armstrong ◽  
Steven X. Cadrin
Keyword(s):  
Population Structure ◽  
Site Fidelity ◽  
Gadus Morhua ◽  
Fishery Management ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Scientific Uncertainty ◽  
Spawning Site ◽  
Metapopulation Structure ◽  
Spawning Sites

Rebuilding the Gulf of Maine stock of Atlantic cod (Gadus morhua) has been much slower than expected. An important source of scientific uncertainty contributing to the difficulties in managing rebuilding has been the lack of understanding of cod population structure. Previous research indicates that the stock functions as a metapopulation that is made up of multiple subpopulations and many finer-scale spawning components. This study investigated fine-scale, multiyear spawning site fidelity by a spring-spawning component of Atlantic cod in the western Gulf of Maine. Movements of acoustically tagged cod (n = 63) with respect to a known spawning site were tracked using passive acoustic telemetry. A large proportion (38–67%) of tagged cod exhibited spawning site fidelity between 2010 and 2012. After adjusting for fishing mortality, natural mortality, and skipped spawning, the estimated rate of spawning site fidelity ranged between 47 and 95% in 2011. Multiyear spawning site fidelity was also observed, with individuals being tracked for up to four consecutive spawning seasons. Spawning site fidelity serves as one of the multiple mechanisms that contribute to the formation and maintenance of the observed metapopulation structure. Spawning site fidelity also reduces the reproductive connectivity among spawning sites, thus delaying both recolonization of abandoned spawning sites and stock rebuilding. Future stock assessment models and fishery management plans that incorporate the metapopulation structure of cod in the Gulf of Maine are expected to be more effective at preventing continued declines in spawning diversity and promoting rebuilding.

Discrimination of wild and farmed Atlantic cod (Gadus morhua) based on morphology and scale-circuli pattern

2011 ◽  
Vol 68 (9) ◽  
pp. 1928-1936 ◽  
Author(s):  
Ingebrigt Uglem ◽  
Marius Berg ◽  
Rebecca Varne ◽  
Rune Nilsen ◽  
Jarle Mork ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Temporal Distribution ◽  
Ecological Impacts ◽  
Farmed Fish ◽  
In The Wild ◽  
Computer Based ◽  
Spatio Temporal ◽  
Discrimination Methods

Abstract Uglem, I., Berg, M., Varne, R., Nilsen, R., Mork, J., and Bjørn, P. A. 2011. Discrimination of wild and farmed Atlantic cod (Gadus morhua) based on morphology and scale-circuli pattern. – ICES Journal of Marine Science, 68: 1928–1936. To evaluate the spatio–temporal distribution and ecological impacts of escaped farmed Atlantic cod (Gadus morhua), it is necessary that escapees can be traced in the wild. To do this, simple, reliable, and fast methods for determining the origin of cod are required. The aim of this proof-of-concept study was to evaluate whether simple analyses of scales and body morphology can distinguish between wild and farmed cod. Digital images of fish and scales from adult cod from two farms, and wild cod caught near these farms, were analysed by computer-based image analyses. By combining mean breadth of circuli and length-adjusted scale radius in a discriminant analysis, 86 and 80% of wild and farmed fish, respectively, were correctly classified. Moreover, using three simple morphometric measures representing dorsal fin size, neck curvature, and length of lower jaw, 100 and 95% of wild and farmed cod, respectively, were classified correctly. To validate these discrimination methods further, an expanded analysis of additional farmed and wild cod populations is required. The results pave the way for the development of a reliable and standardized methodology for classification of the origin of cod caught in the wild.

Seasonal movements and connectivity of an Atlantic cod (Gadus morhua) spawning component in the western Gulf of Maine

2017 ◽  
Vol 74 (6) ◽  
pp. 1780-1796 ◽  
Author(s):  
Douglas R. Zemeckis ◽  
Chang Liu ◽  
Geoffrey W. Cowles ◽  
Micah J. Dean ◽  
William S. Hoffman ◽  
...  
Keyword(s):  
Population Structure ◽  
Data Storage ◽  
Gadus Morhua ◽  
Fishery Management ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Stock Assessment ◽  
Movement Patterns ◽  
Seasonal Movements ◽  
Spawning Sites

Abstract Movement patterns of marine fishes can have considerable impacts on their population dynamics. A thorough understanding of fish movements is therefore required for informing stock identification, stock assessment, and fishery management. This study investigated the seasonal movements and connectivity of a spring-spawning component of Atlantic cod (Gadus morhua) in the western Gulf of Maine. From 2010 through 2013, spawning cod were sampled within an inshore spawning closure and tagged with conventional tags (n = 2368), acoustic transmitters (n = 106), and archival data storage tags (n = 266). Acoustic receivers were deployed on three inshore spawning sites to test for connectivity among sites. Data from archival tags were used to describe seasonal habitat occupancy and movement patterns via geolocation to statistical areas. Tagging data indicated that cod were primarily residential in the western Gulf of Maine, moving inshore to spawn during the spring (April–July), followed by an offshore migration to their feeding grounds for summer and fall. Cod generally inhabited waters from 45 to 175 m, with the deep offshore basins (>150 m) serving as overwintering habitat. Occupied water temperatures ranged from 4.0 to 13.3 °C, with the coldest temperatures experienced from March through July and the warmest temperatures experienced from September through January. Results provided evidence of spawning site fidelity and connectivity among spawning sites, with some fish visiting multiple spawning sites within or between years. The movements observed during and after the spring-spawning season serve as important mechanisms influencing metapopulation dynamics in the Gulf of Maine region, including both fine- and broad-scale population structure. The improved understanding of cod movement patterns will assist fishery managers in developing management plans, including spawning protection measures, and help to address remaining uncertainties with respect to cod population structure in the Gulf of Maine and other regions.

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