The ecology of gadid fishes in the circumpolar Arctic with a special emphasis on the polar cod (Boreogadus saida) (original) (raw)
Related papers
Size, age and diet of polar cod, Boreogadus saida (Lepechin 1773), in ice covered waters
Polar Biology, 1989
Polar cod (Boreogadus saida) associated with drifting sea-ice were collected in the western Barents sea and north of Svalbard with dip-nets while SCUBA-diving in 1986 and 1987. Length-frequency measurements and otolith-readings suggested that the specimens were either one or two years old. The diet of fish from the western Barents sea (first-year ice) consisted mainly of copepods (Calanus finmarchicus, Calanus glacialis) and the hyperiid amphipod Parathemisto libellula. Fish collected north of the Svalbard archipelago (multi-year ice) had a more diverse diet, in which P. libellula and the sympagic amphipod Apherusa glacialis contributed more to the total diet biomass than copepods.
Polar Biology
Polar cod (Boreogadus saida) and saffron cod (Eleginus gracilis) are key fishes in the Arctic marine ecosystem, serving as important trophic links between plankton and apex predators, yet our understanding of their life histories in Alaska's Arctic is extremely limited. To improve our knowledge about their early life stages (ELS), we described the spatial and temporal distributions of preflexion larvae to late juveniles (to 65 mm in length) in the Chukchi and western Beaufort seas based on surveys conducted between 2004 and 2013, and examined how their abundances varied in response to environmental factors. Species-specific differences in habitat use were found, with polar cod having a more offshore and northern distribution than saffron cod, which were found closer inshore and farther south. Polar cod preflexion and flexion larvae were encountered throughout the sampling season across much of the shelf, which suggests that spawning occurs over several months and at multiple locations, with Barrow Canyon potentially serving as an important spawning and/or retention area. Polar cod ELS were abundant at intermediate temperatures (5.0-6.0 °C), while saffron cod were most abundant at the highest temperatures, which suggests that saffron cod may benefit from a warming Arctic, while polar cod may be adversely affected. This research provides new insights into how environmental variability influences the distribution and abundance of gadids in the Pacific Arctic and advances our understanding of the habitats occupied by these key forage species during their first few months of life.
Arctic Science
Arctic cod (Boreogadus saida) are often found in front of glaciers, which is the least studied of the species' habitats. Uummannap Kangerlua and Sullorsuaq in West Greenland provide a unique opportunity to study Arctic cod in the glacial habitat, as they are among the few places with a directed Arctic cod fishery. Inuit fishers from these fjords regularly catch Arctic cod as fresh bait for the Greenland halibut (Reinhardtius hippoglossoides) longline fishery, the main economic activity in the region. We collaborated with the fishers to learn about Arctic cod through interviews and collection of fish samples. Ten informants provided information on fishing areas, fishing methods, interannual variability in the catches, relationships with temperature and sea ice, and reported a spawning area near Saattut. One of the two samples collected contained only 21% males, which were longer, heavier, older, and had a higher gonadosomatic index than females. This skewed sex ratio may result f...
Polar Biology, 2011
During a recent period of increased influx of warm Atlantic water to the western coast of Svalbard, we have observed a northward expansion of boreal Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) into areas dominated by the native polar cod (Boreogadus saida). To determine the potential impact of new ecological interactions, we studied the diet of co-occurring juvenile gadoids in fjords, open water, and sea ice around Svalbard. We also reviewed the available literature on polar cod feeding in different habitats across the Arctic to determine whether region, habitat, or fish size may influence diet. Feeding by polar cod in the pelagic zone was size dependent, with small fish primarily consuming Calanus spp. and smaller copepods, with an increasing ration of Themisto spp. at larger sizes. In benthic habitats, diets were more varied and included considerably more unidentified material and sediment. Less than 40% dietary overlap was detected among the three species when they were found together. Stable isotope analyses indicated these patterns were representative of longer-term assimilation. The low interspecific dietary overlap suggests little direct competition. Future increases in abundance and the high predation potential of the boreal taxa, however, may impact the persistence of polar cod on some Arctic shelves.
Journal of Marine Systems, 2011
The distribution and diet of larval and juvenile Arctic cod (Boreogadus saida) were studied during summer 2005 in the coastal Canadian Beaufort Sea. A total of 275 individuals were captured and the highest abundance was observed at station depths of 20-30 m. This corresponds well with the location of the frontal zone where the Mackenzie River plume water and open sea water meet. Diet examinations were performed on 220 Arctic cod, which were found undamaged from sampling. We observed a gradual decrease in prey number per fish and increase in prey size as larvae grew which corresponded to a shift from Rotifera and nauplii towards larger copepodid stages. However, at all sizes, the larvae remain generalists and feed on a broad range of organisms. Environmental changes due to climate warming could have a twofold impact on fish larvae feeding in the studied region. First, the potential for increased primary production may lead to increased zooplankton production that may impact the feeding and nutrition positively. On the other hand, greater discharge of turbid water from the Mackenzie River may reduce light penetration in the water column that may negatively influence the ability of visual predators to successively forage.
Revision of the Arctic cod genus Arctogadus
Journal of Fish Biology, 2003
Examination of 200 specimens (54-477 mm L S ) of the high Arctic cod genus Arctogadus showed that A. borisovi should be considered a junior synonym of A. glacialis. The most important specific characters hitherto used, i.e. length of barbel, interorbital width, horizontal diameter of eye and number of rakers on the anterior gill arch, were shown to be strongly affected by allometric change and were not of specific diagnostic value. A redescription of A. glacialis is given with new information on its biology.
Diets and body condition of polar cod (Boreogadus saida) in the northern Bering Sea and Chukchi Sea
Polar Biology, 2015
To understand trophic responses of polar cod Boreogadus saida (a key species in Arctic food webs) to changes in zooplankton and benthic invertebrate communities (prey), we compared its stomach contents and body condition between three regions with different environments: the northern Bering Sea (NB), southern Chukchi Sea (SC), and central Chukchi Sea (CC). Polar cod were sampled using a bottom trawl and their potential prey species in the environment were sampled using a plankton net and a surface sediment sampler. Polar cod fed mainly on appendicularians in the NB and SC where copepods were the most abundant in the environment, while they fed on copepods, euphausiids, and gammariids in the CC where barnacle larvae were the most abundant species in plankton samples on average. The stomach fullness index of polar cod was higher in the NB and SC than CC, while their body condition index did not differ between these regions. The lower lipid content of appendicularians compared to other prey species is the most plausible explanation for this inconsistency.