Seasonal variation in temperature preference of juvenile Atlantic cod (Gadus morhua), with evidence supporting an energetic basis for their diel vertical migration

1991 ◽  
Vol 69 (5) ◽  
pp. 1302-1307 ◽  
Author(s):  
Donald S. Clark ◽  
John M. Green
Keyword(s):  
Seasonal Variation ◽  
Vertical Migration ◽  
Diel Vertical Migration ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Energetic Efficiency ◽  
Temperature Preference ◽  
Ambient Temperatures ◽  
Inshore Waters ◽  
Conception Bay

Juvenile (3-year-old) Atlantic cod (Gadus morhua) from Broad Cove, Conception Bay, Newfoundland, exhibit seasonal variation in temperature preference. Laboratory studies show that juvenile cod from ambient temperature water prefer temperatures that correlate closely with seasonal changes in the temperature of the inshore waters that they inhabit. A similar pattern is shown by fish held in 10 °C water over winter, indicating that variation in temperature preference is not simply a response to changing ambient temperatures but occurs in an anticipatory manner that allows them to maintain their physiologically optimal temperature at a seasonally appropriate level. The results also support the hypothesis that the diel vertical migration of juvenile cod in summer increases energetic efficiency by reducing metabolic costs in nonfeeding hours.

Activity and movement patterns of juvenile Atlantic cod, Gadus morhua, in Conception Bay, Newfoundland, as determined by sonic telemetry

1990 ◽  
Vol 68 (7) ◽  
pp. 1434-1442 ◽  
Author(s):  
Donald S. Clark ◽  
John M. Green
Keyword(s):  
Feeding Behaviour ◽  
Gadus Morhua ◽  
Cold Water ◽  
Atlantic Cod ◽  
Activity Patterns ◽  
Energetic Efficiency ◽  
Home Ranges ◽  
Depth Range ◽  
Resting Sites ◽  
Conception Bay

We studied the movements and activity patterns of individual 3-year-old (28–33 cm total length) Atlantic cod, Gadus morhua, in Conception Bay, Newfoundland, using sonic telemetry. Cod tracked between June and early September (summer) were wide ranging (> 3 km/day), nocturnally active, and migrated daily between deep (30 m) cold water where they were inactive and shallow (< 15 m) warm water where they fed. Cod tracked between mid-September and December (autumn) stayed in shallow (< 20 m) water where they were active in relatively small (545.3–2581.6 m2) home ranges during daylight hours and inactive at consistent resting sites at night. Home ranges were over sand whereas resting sites were generally in rocky areas. The seasonal change in migratory behaviour coincided with the disappearance of the shallow (< 30 m) summer thermocline. When the water column became isothermal over the depth range of juvenile cod, they remained in shallow feeding areas throughout the diel period. We suggest that the summer diel migration is a strategy to increase energetic efficiency. Literature on the feeding behaviour of cod and on the predation of juvenile cod suggests that the switch from nocturnal to diurnal activity may be an antipredator strategy. However, more information on the feeding behaviour of cod is required before this hypothesis can be adequately evaluated.

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.

Seasonal Changes in General Condition and Lipid Content of Cod from Inshore Waters

1967 ◽  
Vol 24 (3) ◽  
pp. 607-612 ◽  
Author(s):  
P. M. Jangaard ◽  
H. Brockerhoff ◽  
R. D. Burgher ◽  
R. J. Hoyle
Keyword(s):  
Seasonal Variation ◽  
Nova Scotia ◽  
Lipid Content ◽  
General Condition ◽  
Seasonal Variations ◽  
Seasonal Changes ◽  
Oil Content ◽  
Gadus Morhua ◽  
Male Fish ◽  
Inshore Waters

The seasonal variations in lipid content and general "condition" of cod, Gadus morhua L., from an inshore population have been determined.Four female and four male fish were chosen from 20 live cod brought in monthly from Terence Bay, Halifax County, Nova Scotia, the fish were pooled and the lipid content determined on the flesh, livers, and gonads. The flesh lipids varied from 0.57% to 0.74% and the oil content of the livers from 15% to 75%.The general "condition" of the fish as expressed by [Formula: see text], the liver condition by [Formula: see text], and the fat content of the liver all showed seasonal variation with maxima in the fall and minima in the spring. KF varied from 0.79 to 1.05 and KL from 1.0 to 4.5. No seasonal variation in the amount of flesh lipids could be detected.

scholarly journals Vertical migration in adult Atlantic cod (Gadus morhua)

2007 ◽  
Vol 64 (12) ◽  
pp. 1747-1760 ◽  
Author(s):  
Espen Strand ◽  
Geir Huse
Keyword(s):  
Vertical Migration ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Pelagic Zone ◽  
Neutral Buoyancy ◽  
Visual Predation ◽  
Trade Offs ◽  
Key Factor ◽  
Pelagic Prey ◽  
Benthic Prey

We investigate the trade-offs associated with vertical migration and swimming speed of Atlantic cod (Gadus morhua) using an adaptive individual-based model. Simulations with varying distribution and occurrence of prey, with and without swimbladder constraints, and visual predation were performed. Most simulations resulted in cod migrations between the bottom and pelagic zones. In simulations with high probability of encountering pelagic prey, the cod spent the daytime in the pelagic zone, moving to the bottom to feed only when no pelagic prey were encountered. At night the cod stayed in the pelagic zone to attain neutral buoyancy. In simulations with low occurrence of pelagic prey or high visual predation pressure, the cod remained at the bottom feeding on the consistently present benthic prey. If the pelagic prey occurred far above the sea floor or there were no benthic prey, the cod abandoned all bottom contact. The study thus predicts that the probability of encountering energy-rich pelagic prey is the key factor in driving vertical migration in adult cod. Buoyancy regulation is further shown to be an important constraint on vertical migration.

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.

Overwintering of Adult Northern Atlantic Cod (Gadus morhua) in Cold Inshore Waters as Evidenced by Plasma Antifreeze Glycoprotein Levels

1994 ◽  
Vol 51 (12) ◽  
pp. 2834-2842 ◽  
Author(s):  
Sally V. Goddard ◽  
J. S. Wroblewski ◽  
C. T. Taggart ◽  
K. A. Howse ◽  
W. L. Bailey ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Antifreeze Glycoproteins ◽  
Cold Temperatures ◽  
Antifreeze Glycoprotein ◽  
Trap Fishery ◽  
In The Wild ◽  
History Of ◽  
Inshore Waters ◽  
Trinity Bay

Adult Atlantic cod (Gadus morhua) are known to produce antifreeze glycoproteins in response to cold temperatures. Our laboratory studies demonstrated that blood plasma levels in adult cod were positively correlated with the number of days they spent in subzero water. Between April 1991 and June 1993, we monitored concentrations of antifreeze glycoproteins in the plasma of late juvenile and adult cod in Trinity Bay, Newfoundland, and used the results to estimate how long cod had been exposed to low water temperatures. A consideration of these data in conjunction with detailed temperature profiles of the area taken over the course of the study allowed us to deduce the distribution of cod in relation to the temperature field. This study provides evidence that (1) blood antifreeze glycoprotein levels can be used to deduce the recent thermal history of cod in the wild and (2) after their inshore summer feeding period, considerable numbers of adult cod overwintered inshore in Trinity Bay in subzero water, producing antifreeze glycoproteins as temperatures fell below 0 °C. From May onwards, "cold-adapted" cod moved into warming surface waters, where they became available to an early inshore trap fishery.

A Bioenergetics Analysis of Diel Vertical Migration by Kokanee Salmon, Oncorhynchus nerka

1993 ◽  
Vol 50 (11) ◽  
pp. 2336-2349 ◽  
Author(s):  
Mark S. Bevelhimer ◽  
S. Marshall Adams
Keyword(s):  
Vertical Migration ◽  
Diel Vertical Migration ◽  
Oncorhynchus Nerka ◽  
General Rule ◽  
Foraging Efficiency ◽  
Energetic Efficiency ◽  
Net Energy ◽  
Migration Strategy ◽  
Kokanee Salmon ◽  
Growth Maximization

Diel vertical migration of fishes is probably a result of the combined effects of several selective forces, including predator avoidance, foraging efficiency, and bioenergetic efficiency. We considered both foraging efficiency and energetic efficiency as a combined effect which we called growth maximization. The importance of growth maximization as a selective force was evaluated with a bioenergetics-based model to estimate growth rates of various migration scenarios of kokanee salmon, Oncorhynchus nerka. Environmental parameters (temperature and zooplankton distributions) in the model were obtained from a North Carolina reservoir with an established population of kokanee. The simulations demonstrated that vertical migrations can be energetically advantageous when kokanee and their prey are thermally segregated and that ontogenetic and seasonal differences in the optimal migration strategy should be expected. The general rule for vertical migration as determined from the simulations is to feed where net energy intake is maximized and then reside when not feeding where energetic costs are minimized and food is digested to the point that consumption during the next feeding period is not limited by the amount of undigested food remaining in the stomach. Data obtained from vertical gill nets and hydroacoustics were compared with model predictions.

scholarly journals Variant colourations of Atlantic cod (Gadus morhua) in Newfoundland and Labrador nearshore waters

2004 ◽  
Vol 61 (5) ◽  
pp. 752-759 ◽  
Author(s):  
Karen R. Gosse ◽  
Joseph S. Wroblewski
Keyword(s):  
Continental Shelf ◽  
Newfoundland And Labrador ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Experimental Period ◽  
Fish Prey ◽  
Northwest Atlantic ◽  
Inshore Waters ◽  
The Stability

Abstract Adult cod (Gadus morhua) inhabiting continental shelf waters of the Northwest Atlantic typically display a countershaded colouration: a dark back gradating to a light underbelly. Some cod in Newfoundland and Labrador inshore waters have predominantly brown or red pigmentation. Cod inhabiting Gilbert Bay in Labrador often have golden-brown colouration, likely the result of an invertebrate diet rich in carotenoids, and are known in the vernacular as the “golden cod of Labrador”. To determine the stability of these variant colourations, we captured cod from Gilbert Bay, held them in a net pen and fed them a diet of fish. Over the 12-week experimental period, the variant coloured cod lost much of their brown or red pigmentation, and became countershaded. Because of its impermanence when cod switch from invertebrate to fish prey, variant colouration of cod can provide only provisional information about stock origin.

Antifreeze Production, Freeze Resistance, and Overwintering of Juvenile Northern Atlantic Cod (Gadus morhua)

1992 ◽  
Vol 49 (3) ◽  
pp. 516-522 ◽  
Author(s):  
Sally V. Goddard ◽  
Ming H. Kao ◽  
Garth L. Fletcher
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fish Length ◽  
Antifreeze Glycoproteins ◽  
Freeze Resistance ◽  
Ambient Temperatures ◽  
Temperature Regimes ◽  
Northern Atlantic ◽  
Freezing Temperatures ◽  
Cycling Temperature

Four size groups of northern Atlantic cod (Gadus morhua) (juveniles < 15, 15–25, and 26–40 cm and adults > 50 cm) were investigated over a winter cycle for their ability to increase freeze resistance by producing plasma antifreeze glycoproteins. All juveniles had significantly higher plasma antifreeze levels than adults during the winter (January–March) under similar conditions of cycling temperature and ambient photoperiod. Highest winter plasma antifreeze levels and lowest plasma freezing temperatures were consistently found in the 15–25 cm group. Fish length and plasma antifreeze levels were inversely related from January to April, with the exception of the 0 + cod. All juvenile groups developed considerable freeze protection early in the winter cycle before the onset of freezing temperatures. However, the adults were not significantly protected until the end of January, when ambient temperatures had fallen below 0 °C. The 15–25 cm cod were held in three cycling temperature regimes. Induction temperatures for antifreeze production in this size group appeared to be between 2 and 3 °C, as compared with between 1 and 0 °C for the adults. We suggest that these patterns of antifreeze production may have direct bearing on habitat selection and overwintering behaviour of the northern Atlantic cod at different stages of development.

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