Shallow-Water Scavengers of Polar Night and Day – An Arctic Time-Lapse Photography Study

Until recently, polar night constituted truly a “mare incognitum” of our times. Yet, the first records from this very little-explored period showcased a surprisingly rich and active ecosystem. This investigation aims to reveal the level of scavenger activity during both Arctic polar night and day. It compares the shallow-water scavenging fauna observed during two contrasting seasons (winter vs. summer) in a high Arctic fjord (Kongsfjorden, 79° N, Spitsbergen, Svalbard Archipelago). In each of January and July 2015, two different bait types – Atlantic cod (Gadus morhua) and a bird carcass (chicken meat) were deployed at a depth of 12 m. Fauna were monitored remotely using time-lapse cameras equipped with bait traps, with photographs taken every 15 min over a period of 4 days. Thirty taxa were recorded at baits, dominated by lysianassid amphipods (Onisimus sp. 88%, Anonyx sp. 2%, but only during winter), and buccinid gastropods (B. undatum 5%, B. glaciale 1%, Buccinum sp. 3%, in both seasons). In most cases, buccinids were the first animals to appear at bait. The total number of recorded taxa, mean species richness per sampling unit, total abundance and associations among taxa were higher, on average, in winter than in summer deployments, while Pielou’s evenness index showed the opposite pattern. Scavenger assemblages differed significantly between the two seasons and also in response to the two different bait types, with seasonal effects being strongest. Contrary to expectations, bait consumption rates differed very little between the two seasons, being slow in general and only slightly faster in summer (0.05 g of cod bait consumed in 1 min) compared to winter (0.04 g min–1), yielding novel insights into ecological interactions and functions in shallow marine ecosystems during Arctic polar nights.

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

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f93-142 ◽

1993 ◽

Vol 50 (6) ◽

pp. 1255-1264 ◽

Cited By ~ 35

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.

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Benthic scavenger community composition and carrion removal in Arctic and Subarctic fjords

Polar Biology ◽

10.1007/s00300-020-02773-5 ◽

2020 ◽

Author(s):

K. Dunlop ◽

P. E. Renaud ◽

J. Berge ◽

D. O. B. Jones ◽

R. P. Harbour ◽

...

Keyword(s):

Gadus Morhua ◽

Atlantic Cod ◽

Benthic Communities ◽

Time Lapse ◽

Atlantic Water ◽

Clupea Harengus ◽

Removal Rates ◽

Ecosystem Responses ◽

Mean Values ◽

The Mean

AbstractIn high latitude coastal regions, benthic scavenger communities are largely composed of invertebrates that play a key role in the cycling of organic matter. Factors including temperature and depth can structure Arctic and Subarctic fjord benthic communities, but the response of scavenging communities to these factors is poorly known. To address this, we compared scavenging fauna in eight fjords with different physical characteristics in Svalbard and northern Norway using time-lapse imagery of scavengers consuming Atlantic herring (Clupea harengus) bait. Fjords influenced by relatively warm Atlantic waters, both in Norway and Svalbard, had high scavenger richness. However, Svalbard fjords with negative bottom temperatures had the lowest species richness and were dominated by lysianassoid amphipods and ophiuroids. In these cold Svalbard fjords, the mean carrion removal rates were almost 20 times higher than mean values noted elsewhere, except in the warm Norwegian fjord Kaldfjorden. Amphipods and ophiuroids quickly reduced the bait to bones (207.6–304.7 g removed per hour (g h−1); mean 290.6 ± 7.3 g h−1, n = 4) in cold Svalbard fjords. In the warmer Svalbard fjords, carrion removal rates were low (0–51.5 g h−1; mean 14.6 ± 9.0 g h−1, n = 5). Carrion removal rates in Kaldfjorden were higher than other Atlantic Water influenced fjords (132.1 and 372.5 g h−1, n = 2) owing to the scavenging activity of Atlantic cod (Gadus morhua). The results demonstrate potential ecosystem responses to warming in Arctic and Subarctic fjords, particularly effects related to range expansion of boreal species.

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Occurrence of anisakid nematodes in Atlantic cod (Gadus morhua) and Greenland cod (Gadus ogac), West Greenland

Acta Parasitologica ◽

10.2478/s11686-010-0009-3 ◽

2010 ◽

Vol 55 (1) ◽

Cited By ~ 18

Author(s):

Kim Mouritsen ◽

Rasmus Hedeholm ◽

Henriette Schack ◽

Lone Møller ◽

Marie Storr-Paulsen ◽

...

Keyword(s):

Gadus Morhua ◽

Atlantic Cod ◽

Infection Intensity ◽

Stomach Contents ◽

Nematode Species ◽

Commercial Fishing ◽

Opposite Pattern ◽

West Greenland ◽

Pcr Rflp ◽

Anisakid Nematodes

AbstractAnisakid nematodes commonly infect gadids, and are of economic and aesthetic importance to the commercial fishing industry in Greenland as some species are pathogenic to humans. However, very little is known about the occurrence of these parasites and their impact on the hosts in Greenland waters. During a survey in 2005, stomach sample of 227 Atlantic cod (Gadus morhua) and 64 Greenland cod (Gadus ogac) was collected in Godthaab and Sisimiut fiord systems in West Greenland waters. All cod were dissected for stomach contents and anisakid nematodes were removed from the visceral cavity. Third stage larvae (L3) of three anisakid species were found, including Contracaecum osculatum (Rudolphi, 1802), Anisakis simplex (Rudolphi, 1809) and Hysterothylacium aduncum (Rudolphi, 1802). Molecular identification by PCR-RFLP indicated the presence of A. simplex s.s. and the sibling species C. osculatum B and C. The prevalence of infection by C. osculatum was higher in Greenland cod (84.3%) than in Atlantic cod (73.9%) whereas the prevalence of A. simplex showed an opposite pattern (Greenland cod 8.3%; Atlantic cod 24.2%). Only one G. morhua (1.0%) was infected by H. aduncum. No gender specific difference in both nematode species regarding prevalence of infection and mean infection intensity was evident, and there was no relationship between fish condition and the intensity of nematode infections. Standardised for size, capelin-eating cod were in better condition and more heavily infected than fish subsisting on alternative prey at the point of collection. Hence, nematode infections in the two gadids seem governed in part by feeding behaviour, and capelin appears a significant source of larval anisakids.

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Effects of temperature on life history set the sensitivity to fishing in Atlantic cod Gadus morhua

Marine Ecology Progress Series ◽

10.3354/meps10943 ◽

2014 ◽

Vol 514 ◽

pp. 217-229 ◽

Cited By ~ 11

Author(s):

HY Wang ◽

LW Botsford ◽

JW White ◽

MJ Fogarty ◽

F Juanes ◽

...

Keyword(s):

Life History ◽

Gadus Morhua ◽

Atlantic Cod ◽

Effects Of Temperature

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Responses of Atlantic cod Gadus morhua head kidney leukocytes to phytase produced by gastrointestinal-derived bacteria

Fish Physiology and Biochemistry ◽

10.1007/s10695-009-9364-0 ◽

2009 ◽

Vol 36 (4) ◽

pp. 883-891 ◽

Cited By ~ 14

Author(s):

Carlo C. Lazado ◽

Christopher Marlowe A. Caipang ◽

Sanchala Gallage ◽

Monica F. Brinchmann ◽

Viswanath Kiron

Keyword(s):

Gadus Morhua ◽

Atlantic Cod ◽

Head Kidney

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Some recent data on sperm morphology and motility kinetics in Atlantic cod (Gadus morhua L.)

Fish Physiology and Biochemistry ◽

10.1007/s10695-020-00915-4 ◽

2021 ◽

Author(s):

Sayyed Mohammad Hadi Alavi ◽

Azadeh Hatef ◽

Ian A.E. Butts ◽

Olga Bondarenko ◽

Jacky Cosson ◽

...

Keyword(s):

Gadus Morhua ◽

Sperm Morphology ◽

Atlantic Cod

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Natural mortality from poor condition in Atlantic cod (Gadus morhua)

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f00-023 ◽

2000 ◽

Vol 57 (4) ◽

pp. 826-836 ◽

Cited By ~ 96

Author(s):

Jean-Denis Dutil ◽

Yvan Lambert

Keyword(s):

Gadus Morhua ◽

Atlantic Cod ◽

Negative Impact ◽

Fish Muscle ◽

Early Summer ◽

Wild Fish ◽

Natural Mortality ◽

Muscle Lactate ◽

Lactate Dehydrogenase Activity ◽

Poor Condition

The extent of energy depletion was assessed in Atlantic cod (Gadus morhua) in spring and early summer (1993-1995) to assess relationships between poor condition and natural mortality. Several indices of condition were compared in wild fish in the northern Gulf of St. Lawrence and in fish exposed to a prolonged period of starvation in laboratory experiments. Discriminant analyses classified only a small fraction of the wild fish as similar to cod that did not survive and a much larger fraction as similar to cod that survived starvation. This percentage increased from April to May and peaked in June 1993 and 1994. Condition factor and muscle somatic index allowed a clear distinction between live and dead fish. Muscle lactate dehydrogenase activity suggested that cod had experienced a period of negative growth early in 1993, 1994, and 1995. Fish classified as similar to starved individuals were characterized by a higher gonad to liver mass ratio than others. Reproduction may have a negative impact on survival not only in spring but also later into summer, as some individuals were found not to have recovered by late summer. This study shows that natural mortality from poor condition contributed to lower production in the early 1990s.

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