scholarly journals Status and biology of harbour seals (Phoca vitulina) in Svalbard

2010 ◽  
Vol 8 ◽  
pp. 47 ◽  
Author(s):  
Christian Lydersen ◽  
Kit M Kovacs
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Growth Curves ◽  
Reproductive Rate ◽  
Time Of Day ◽  
Small Population ◽  
Polar Cod ◽  
Adult Males ◽  
Adult Females ◽  
Harbour Seals

Harbour seals in Svalbard are the northernmost population of this species. This small population is comprised of ca. 1,000 individuals, most of which reside along the west coast of Prins Karls Forland (78°20’N). Satellite tracking studies have shown that adults are resident. Birthing occurs in the latter half of June. Newborns weigh about 11 kg and gain an average of 0.7 kg/d during the nursing period. Haulout patterns in Svalbard harbour seals are influenced by date (season), time of day, tidal cycle and temperature. Moulting takes place in early fall, first among juveniles, then in adult females and finally in adult males. Feeding studies show that polar cod (Boreogadus saida) is the dominant prey in terms of numbers, while Atlantic cod (Gadus morhua) is the dominant prey based on biomass, at least during the early autumn. Growth curves display significant sexual dimorphism with asymptotic values for standard length and body mass being greater formales. Testosterone levels inmales showed an abrupt increase at 6 years of age, while estradiol levels in females increased abruptly from age 4 years. The reproductive rate for adult females was 0.93. Longevity of Svalbard harbour seals is very short compared with populations from other areas.

Time-Budgets of Camargue Horses Ii. Time-Budgets of Adult Horses and Weaned Sub-Adults

Behaviour ◽  
1980 ◽  
Vol 72 (1-2) ◽  
pp. 26-48 ◽  
Author(s):  
Patrick Duncan
Keyword(s):  
Social Structure ◽  
Social System ◽  
General Trend ◽  
Small Population ◽  
Time Budgets ◽  
Adult Males ◽  
Adult Females ◽  
Young Horses

AbstractTime-budgets of adult and weaned sub-adult horses were studied in a small population of Camargue horses living in semi-liberty. The categories of activities used were: Standing resting, Lying flat, Lying up, Standing alert, Walking, Trotting, Galloping, Rolling and Foraging. The main differences in time-budgets were related to age and to sex : young horses spent more time lying (sleeping), males spent more time standing alert and in rapid movements (trot, gallop), while usually foraging less than did the adult females. During the three years of the study the population increased from 20 to 54 horses and there were considerable changes in social structure as the number of adult males increased. Associated with these developments there were some changes between years in the time-budgets: the most striking of which was a general trend for all horses to spend less time lying. Nonetheless the time-budgets showed a considerable constancy across years and age/sex-classes, especially with regard to time spent foraging. This conclusion may provide a clue as to why horses have an unusual social system based on long term relationships between a male and the females of his harem.

What is the carrying capacity for fish in the ocean? A meta-analysis of population dynamics of North Atlantic cod

2001 ◽  
Vol 58 (7) ◽  
pp. 1464-1476 ◽  
Author(s):  
Ransom A Myers ◽  
Brian R MacKenzie ◽  
Keith G Bowen ◽  
Nicholas J Barrowman
Keyword(s):  
North Atlantic ◽  
Carrying Capacity ◽  
Empirical Bayes ◽  
Gadus Morhua ◽  
Mixed Model ◽  
Atlantic Cod ◽  
Unit Area ◽  
Meta Analysis ◽  
Reproductive Rate ◽  
Parameter Estimates

Population and community data in one study are usually analyzed in isolation from other data. Here, we introduce statistical methods that allow many data sets to be analyzed simultaneously such that different studies may "borrow strength" from each other. In the simplest case, we simultaneously model 21 Atlanic cod (Gadus morhua) stocks in the North Atlantic assuming that the maximum reproductive rate and the carrying capacity per unit area are random variables. This method uses a nonlinear mixed model and is a natural approach to investigate how carrying capacity varies among populations. We used empirical Bayes techniques to estimate the maximum reproductive rate and carrying capacity of each stock. In all cases, the empirical Bayes estimates were biologically reasonable, whereas a stock by stock analysis occasionally yielded nonsensical parameter estimates (e.g., infinite values). Our analysis showed that the carrying capacity per unit area varied by more than 20-fold among populations and that much of this variation was related to temperature. That is, the carrying capacity per square kilometre declines as temperature increases.

scholarly journals New encounters in Arctic waters: a comparison of metabolism and performance of polar cod (Boreogadus saida) and Atlantic cod (Gadus morhua) under ocean acidification and warming

Polar Biology ◽  
2016 ◽  
Vol 39 (6) ◽  
pp. 1137-1153 ◽  
Author(s):  
Kristina Lore Kunz ◽  
Stephan Frickenhaus ◽  
Silvia Hardenberg ◽  
Torild Johansen ◽  
Elettra Leo ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Polar Cod ◽  
Boreogadus Saida ◽  
Polar Cod Boreogadus Saida ◽  
And Performance

Antifreeze glycoproteins in the plasma of Newfoundland Atlantic cod (Gadus morhua)

1981 ◽  
Vol 59 (11) ◽  
pp. 2186-2192 ◽  
Author(s):  
Choy L. Hew ◽  
Don Slaughter ◽  
Garth L. Fletcher ◽  
Shashikant B. Joshi
Keyword(s):  
Amino Acid ◽  
High Performance ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Antifreeze Proteins ◽  
Gel Filtration ◽  
Exchange Chromatography ◽  
Polar Cod ◽  
Antifreeze Glycoproteins ◽  
Molecular Weights

The plasma of the Atlantic cod, Gadus morhua, contained antifreeze glycoproteins which were present only during the winter months. The antifreeze proteins were isolated, using gel filtration and ion exchange chromatography, and characterized by high performance liquid chromatography. The antifreeze proteins appeared to consist of at least seven components with molecular weights ranging from 2 500 to 33 000. Chemical analysis of the larger components showed a predominance of alanine, threonine, and galactosamine in a ratio of 2:1:1. The smaller peptides contained proline, in addition to alanine and threonine. The amino acid sequence of the smallest glycopeptide (molecular weight 2500) was found to be Ala Ala Thr Pro Ala Thr Ala Ala Thr Pro Ala Thr Ala Ala.These glycoproteins are very similar, if not identical, in amino acid and carbohydrate composition to those isolated from Antaractic nototheniids and several northern gadoids. The sequence of the smallest glycopeptide from the Atlantic cod is identical to that reported for the polar cod, Boreogadus saida.

Effects of genetic drift in a small population of Atlantic cod (Gadus morhua kildinensis Derjugin) landlocked in a meromictic lake: genetic variation and conservation measures

2015 ◽  
Vol 17 (1) ◽  
pp. 229-238 ◽  
Author(s):  
Lev A. Zhivotovsky ◽  
Anastasia A. Teterina ◽  
Nina V. Mukhina ◽  
Andrei N. Stroganov ◽  
Galina A. Rubtsova ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Genetic Drift ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Small Population ◽  
Meromictic Lake ◽  
Conservation Measures

scholarly journals Barents Sea cod (Gadus morhua) diet composition: long-term interannual, seasonal, and ontogenetic patterns

2019 ◽  
Vol 76 (6) ◽  
pp. 1641-1652 ◽  
Author(s):  
Rebecca E Holt ◽  
Bjarte Bogstad ◽  
Joël M Durant ◽  
Andrey V Dolgov ◽  
Geir Ottersen
Keyword(s):  
Gadus Morhua ◽  
Trophic Ecology ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Prey Size ◽  
Ecosystem Dynamics ◽  
Polar Cod ◽  
Important Species ◽  
Predator Prey ◽  
The North

Abstract Atlantic cod (Gadus morhua) is an ecologically and commercially important species in the North-Atlantic region. Cod is a top predator and information on its trophic ecology is integral for understanding predator–prey relationships and food-web dynamics. We present an analysis of the trophic patterns of Barents Sea (BS) cod using a unique 33-year time-series of stomach-content data from 1984 to 2016. We assessed patterns in diet (prey) composition across years, between seasons, as well as ontogenetic trends in diet, including predator–prey size relationships. Ontogenetic shifts in diet were observed, with fish becoming more important prey with increasing cod size. A very early onset of piscivory was found in <20 cm cod. Cannibalism was found in cod > 20 cm and increased with size. Juvenile cod exhibit a tendency towards consuming prey up to 33% of their body length, whereas larger cod feed on all prey sizes, resulting in asymmetric predator–prey size distributions. Diet varied significantly during 1984–2016, consistent with changes in both prey, cod abundance, and distribution. Seasonal differences were observed; capelin dominated the winter diet, whereas cod, polar cod, and other fish species were prevalent in summer/autumn months. This work represents an important step towards understanding trophic linkages that determine BS ecosystem dynamics.

Seasonal and diel variations of various blood parameters in Atlantic cod (Gadus morhua) and American plaice (Hippoglossoides platessoides)

1993 ◽  
Vol 71 (3) ◽  
pp. 611-618 ◽  
Author(s):  
Céline Audet ◽  
Michel Besner ◽  
Jean Munro ◽  
Jean-Denis Dutil
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Plasma Osmolality ◽  
Blood Parameters ◽  
Time Of Day ◽  
Seasonal Effect ◽  
Lawrence Estuary ◽  
Blood Hemoglobin ◽  
Diel Variations ◽  
Hippoglossoides Platessoides

Seasonal and diel variations of different blood variables were studied in Atlantic cod (Gadus morhua) and American plaice (Hippoglossoides platessoides) subjected to natural fluctuations of salinity and temperature in the St. Lawrence estuary. Significant seasonal fluctuations were found for all the parameters measured (plasma osmolality, Na+, Cl−, K+, glucose, Cortisol, and blood hemoglobin and hematocrit). In cod, the seasonal effect on blood hemoglobin was only detected through its interaction with time of day. In this species, all parameters also varied on an hourly basis, although these changes only represented a small proportion of the variance explained by the statistical model. In plaice, only plasma osmotic composition and blood hematocrit did not show diel variations, while the hour effect was difficult to characterize. In general, though our results indicate that both species acclimated to test conditions, American plaice seemed to cope less efficiently than Atlantic cod with winter conditions. In this respect, the Atlantic cod represents a better candidate for coastal aquaculture in this area.

scholarly journals Feeding habits of harp and hooded seals in Greenland waters

2000 ◽  
Vol 2 ◽  
pp. 50 ◽  
Author(s):  
Finn O Kapel
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Feeding Habits ◽  
Stomach Contents ◽  
Minor Role ◽  
Published Data ◽  
Polar Cod ◽  
Small Fish ◽  
Greenland Halibut ◽  
Important Prey

Results of stomach contents analyses of harp and hooded seals collected in West Greenland waters in the period 1986-1993 are reviewed, and compared with published data and circumstantial information from local hunters. The diet of harp seals in this region is variable but consists mainly of pelagic crustaceans (Thysanoessa spp. and Parathemisto libellula) and small fish species like capelin (Mallotus villosus), sandeel (Ammodytes spp.), polar cod (Boreogadus saida) and Arctic cod (Arctogadus glacialis). Species of importance for commercial fisheries in Greenland, such as Northern prawn (Pandalus borealis), Atlantic cod (Gadus morhua), and Greenland halibut (Reinhardtius hippoglossoides) play a minor role in the diet of harp seals in this area.Variation in the diet of hooded seals is less well documented, but in addition to the species also taken by harp seals, larger demersal fishes like Greenland halibut, redfish (Sebastes spp.), cod, and wolffish (Anarhichas minor) are apparently important prey items.

Evidence of near year-around spawning in Atlantic cod off southern Newfoundland: implications for management

2020 ◽  
Vol 77 (12) ◽  
pp. 1969-1976
Author(s):  
George A. Rose ◽  
Sherrylynn Rowe
Keyword(s):  
Interannual Variability ◽  
Linear Model ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
General Linear Model ◽  
Late Winter ◽  
Random Factor ◽  
Spawning Aggregations ◽  
Adult Females ◽  
Composite Data

Management of Atlantic cod (Gadus morhua) off southern Newfoundland (Northwest Atlantic Fisheries Organization (NAFO) Subdivision 3Ps) entails allocated quotas and restrictions on fishing during late winter and springtime to protect presumed spawning aggregations. We present data collected from research trawls and handlines (1995–2014) indicating spawning inshore may occur near year-around with limited resting from December to February and with more contracted spring spawning possible offshore. A mixed general linear model with binomial error, using year as a random factor, recognized month and length as significant impacts on proportions of females spawning, but not gear or inshore–offshore location. Composite data indicated that females in spawning condition may be present inshore (∼10%–20% of adult females) from March to October. During 1997–1999, with 8–9 months sampled each year, protracted annual spawning schedules and interannual variability were evident. At present, the fishery primarily employs gillnets inshore and otter trawls offshore, with spring spawning closures offering only partial and inconsistent protection. Behavioural interference might be reduced by employing less intrusive longlines, as historically practiced in this fishery.

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