Seasonal variation in the habitat associations of Atlantic cod (Gadus morhua) and American plaice (Hippoglossoides platessoides) from the southern Gulf of St. Lawrence

1998 ◽  
Vol 55 (12) ◽  
pp. 2548-2561 ◽  
Author(s):  
D P Swain ◽  
G A Chouinard ◽  
R Morin ◽  
K F Drinkwater
Keyword(s):  
Seasonal Variation ◽  
Habitat Selection ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Statistical Significance ◽  
Habitat Associations ◽  
Practical Implications ◽  
Hippoglossoides Platessoides ◽  
Trawl Surveys ◽  
Selection Of

We compared habitat associations of southern Gulf of St. Lawrence Atlantic cod (Gadus morhua) and American plaice (Hippoglossoides platessoides) between the summer feeding season on the Magdalen Shallows and the overwintering period in the Cabot Strait. Data were from bottom trawl surveys conducted in September 1993, 1994, and 1995 and January 1994, 1995, and 1996. Both species occupied much deeper, warmer water in winter than in summer. The effect of cod age on temperature distribution reversed between the two seasons, with younger cod occupying warmer water than older cod in summer and colder water in winter. Selection of both depth and temperature by cod tended to be more significant in September than in January. The reduced statistical significance of habitat selection by cod in winter was associated with a more aggregated distribution in this season. The contrast between seasons in habitat associations was particularly strong for plaice. The median habitats occupied by plaice were 58-67 m and -0.1 to 0.3°C in September and 374-426 m and 5.2-5.4°C in January. Habitat selection by plaice was significant in both seasons, but significance tended to be greater in January. Degree of aggregation in plaice distribution was similar between the two seasons. Female plaice occupied significantly warmer water than males in September but not in January. The ecological and practical implications of this striking seasonal variation in habitat associations are discussed.

Age- and Density-Dependent Bathymetric Pattern of Atlantic Cod (Gadus morhua) in the Southern Gulf of St. Lawrence

1993 ◽  
Vol 50 (6) ◽  
pp. 1255-1264 ◽  
Author(s):  
Douglas P. Swain
Keyword(s):  
Habitat Selection ◽  
Density Dependence ◽  
Shallow Water ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Age Groups ◽  
Low Density ◽  
Positive Correlation ◽  
Using Data ◽  
Trawl Surveys

I examined the bathymetric pattern of Alantic cod (Gadus morhua) in September in the southern Gulf of St. Lawrence for age groups 3–8+ over the period 1971–91 using data from annual bottom trawl surveys. Mean age of cod tended to increase with depth in all years. The age-specific bathymetric patterns underlying this relationship differed markedly between periods of low and high abundance. When abundance was high, cod densities tended to be highest at intermediate depths, and the positive correlation between age and depth reflected a tendency for density to be highest in progressively deeper water for older fish. When abundance was low, density was either unrelated to depth or highest in shallow water, and the positive correlation between age and depth reflected a tendency for older cod to be more widely distributed than younger cod (i.e., density decreased less sharply with depth for older cod). I suggest explanations for this density dependence of cod bathymetric pattern and discuss these results in relation to the factors underlying habitat selection and bathymetric segregation by age in this population.

scholarly journals Density-independent and -dependent habitat selection of Atlantic cod (Gadus morhua) based on geostatistical aggregation curves in the northern Gulf of St Lawrence

2010 ◽  
Vol 67 (8) ◽  
pp. 1676-1686 ◽  
Author(s):  
Hacène Tamdrari ◽  
Martin Castonguay ◽  
Jean-Claude Brêthes ◽  
Daniel Duplisea
Keyword(s):  
Habitat Selection ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Local Density ◽  
Abiotic Factors ◽  
Age Groups ◽  
Spatial Dynamics ◽  
Entire Area ◽  
Dynamics Models ◽  
Selection Of

Abstract Tamdrari, H., Castonguay, M., Brêthes, J-C., and Duplisea, D. 2010. Density-independent and -dependent habitat selection of Atlantic cod (Gadus morhua) based on geostatistical aggregation curves in the northern Gulf of St Lawrence. – ICES Journal of Marine Science, 67: 1676–1686. Relationships were sought between local density and population abundance of Atlantic cod (Gadus morhua) in the northern Gulf of St Lawrence (Canada) over its entire area (4RS) and also within a subarea (4R) where the stock has concentrated since it collapsed during the early 1990s. Relationships were analysed using geostatistical aggregation curves computed within the two areas between years of contrasting abundance levels. The curves were interpreted in terms of four conceptual models of spatial dynamics: models D1 and D2, forced mainly by environmental heterogeneity, and models D3 and D4, in which individual behaviour is influenced by local density. Over the entire area, the cod population follows the D2 model for all years and age groups, and it is influenced by abiotic factors. Within the subarea, all four models applied, and the density-dependent basin model (D4) dominated from 2006 to 2008. The year 2006 seems to be pivotal because it coincides with the expansion of the cod population into its former area in the western Gulf (4S).

Seasonal Variation in the Physiological Response of Atlantic Cod (Gadus morhua) to Low Salinity

1992 ◽  
Vol 49 (6) ◽  
pp. 1149-1156 ◽  
Author(s):  
J.-D. Dutil ◽  
J. Munro ◽  
C. Audet ◽  
M. Besner
Keyword(s):  
Skeletal Muscle ◽  
Seasonal Variation ◽  
Osmotic Pressure ◽  
Principal Components ◽  
Physiological Response ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Low Salinity ◽  
Natural Photoperiod ◽  
Highly Correlated

Plasma Na+, Cl−, K+, osmotic pressure, Cortisol, glucose, and protein, blood hemoglobin and hematocrit, and water content of skeletal muscle were measured at regular intervals during a 28-d period following the transfer of Atlantic cod (Gadus morhua) to waters of 7, 14, 21, and 28‰ (control) salinity. These experiments were repeated four times at 3-mo intervals under natural photoperiod and temperatures (0–10 °C). Exposure to 7‰ salinity caused large decreases in plasma Na+ in winter (25 mmol/L over 14 d) and in spring (32 mmol/L over 7 d) when the lowest value for the year was reached (156 mmol/L). Transfer to 14 and 21‰ salinity resulted in a slight decrease (maximum 4%) in plasma Na+ which was much smaller than the seasonal variation (14%) observed in controls. Hydration of skeletal muscle occurred only at 7‰ (2.3% maximum), but these changes were small compared with the seasonal variation (3.9%) observed in the controls. Principal components and clustering analyses showed that all ionic and osmotic variables measured were highly correlated while being only weakly associated with the condition or reproductive status of the fish. There were no indications that acclimation to low salinity was stressful for cod.

Selection of candidate probionts by two different screening strategies from Atlantic cod (Gadus morhua L.) larvae

2010 ◽  
Vol 144 (1-2) ◽  
pp. 153-159 ◽  
Author(s):  
Anders Jón Fjellheim ◽  
Geir Klinkenberg ◽  
Jorunn Skjermo ◽  
Inga Marie Aasen ◽  
Olav Vadstein
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Screening Strategies ◽  
Selection Of

scholarly journals Genetic characteristics of broodstock collected from four Norwegian coastal cod (Gadus morhua) populations

2006 ◽  
Vol 63 (2) ◽  
pp. 209-215 ◽  
Author(s):  
G. Dahle ◽  
K.E. Jørstad ◽  
H.E. Rusaas ◽  
H. Otterå
Keyword(s):  
Gadus Morhua ◽  
White Muscle ◽  
Atlantic Cod ◽  
Genetic Differences ◽  
Offspring Performance ◽  
Genetic Characteristics ◽  
Aquaculture Industry ◽  
Initial Selection ◽  
Selection Of ◽  
Spawning Sites

Abstract The aquaculture industry in Norway is now focused on developing economically viable farming based on the Atlantic cod, Gadus morhua. Extensive research has been carried out on this species for the past two decades, much of it in connection with stock enhancement. Until now, most of the intensive cage culture has been based on wild broodstock. However, a future cod aquaculture industry must be based on a domesticated broodstock, and the initial selection of wild cod becomes an important issue. Genetic differentiation between coastal cod populations in Norway has been reported, and it is of interest to evaluate offspring from some of these populations under farmed conditions. Live mature cod were collected at four selected spawning sites along the Norwegian coast (Porsangerfjord, Tysfjord, Herøy/Helgeland, and Øygarden). The fish were transported to Parisvatnet, a cod aquaculture facility west of Bergen, where they were kept in net pens. Individual tagging and extensive sampling (blood, white muscle, and fin clips) for genetic characterization were carried out. Each potential broodstock fish was genotyped at the haemoglobin and pantophysin I loci in addition to five allozyme (LDH-3∗, GPD∗, IDH-2∗, PGM∗, PGI-1∗) and ten microsatellite loci (Gmo2, Gmo3, Gmo8, Gmo19, Gmo34, Gmo35, Gmo36, Gmo37, Gmo132, Tch11). Comparison of allele frequencies revealed significant genetic differences among some of the coastal cod samples, and offspring performance of the broodstock is now being compared under farmed conditions. The overall test revealed significant genetic differences among the coastal broodstocks, with the HbI, PanI and the microsatellite Gmo132 loci being most informative.

Protein Instability in Minced Flesh from Fillets and Frames of Several Commercial Atlantic Fishes During Storage at −5 C

1975 ◽  
Vol 32 (6) ◽  
pp. 775-783 ◽  
Author(s):  
J. R. Dingle ◽  
J. A. Hines
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Protein Solubility ◽  
Kidney Tissue ◽  
Rapid Loss ◽  
Atlantic Mackerel ◽  
Trimethylamine Oxide ◽  
Minced Fish ◽  
Protein Instability ◽  
Hippoglossoides Platessoides

Minced flesh of Atlantic cod (Gadus morhua) and pollock (Pollachius virens), recovered by means of meat-separator machines from frames left after filleting operations, suffered a rapid loss of protein solubility during storage at −5 C. This was due to the presence of kidney tissue which caused the formation of dimethylamine and formaldehyde from the trimethylamine oxide of the muscle. The minced flesh of witch flounder (Glyptocephalus cynoglossus), American plaice (Hippoglossoides platessoides), and Atlantic mackerel (Scomber scombrus) was relatively stable when mixed with homogenates of their own kidney tissue, but cod kidney caused the same changes in gray sole as it did in minced cod flesh. The exclusion of gadoid kidney and blood from minced fish preparations is recommended.

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