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.

Seasonal changes in the plasma levels of glycoprotein antifreeze, Na+, Cl−, and glucose in Newfoundland Atlantic cod (Gadus morhua)

1982 ◽  
Vol 60 (8) ◽  
pp. 1851-1854 ◽  
Author(s):  
G. L. Fletcher ◽  
D. Slaughter ◽  
C. L. Hew
Keyword(s):  
Seasonal Changes ◽  
Gadus Morhua ◽  
Thermal Hysteresis ◽  
Atlantic Cod ◽  
Freezing Point ◽  
Freezing Point Depression ◽  
Antifreeze Glycoproteins ◽  
Glucose Levels ◽  
Total Plasma Protein ◽  
Two Peaks

A seasonal study was carried out on the hematocrits, plasma freezing point depression, and thermal hysteresis, and plasma Na+, Cl−, total protein, and glucose concentrations in laboratory maintained Atlantic cod. Significant thermal hysteresis was evident in the plasma during the months of January to May indicating the presence of antifreeze glycoproteins. Plasma freezing point depression and Na+ and Cl− concentrations were highest during the winter months and lowest during the summer. Two peaks in glucose levels were evident; one in February and the other in July. No seasonal changes were evident in hematocrits and total plasma protein concentrations.

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 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.

Sign in / Sign up

Export Citation Format

Share Document