A revision of coregonine fish distribution and abundance in eastern James-Hudson Bay

Synopsis Recent sampling programs conducted in the estuaries of the Eastmain and La Grande rivers (James Bay) and the Great Whale, Little Whale, Innuksuac and Povungnituk rivers (Hudson Bay) revealed patterns of coregonine fish distribution that differ from previous observations. The relative abundance of cisco, Coregonus artedii, and lake whitefish, C. clupeaformis, varied among rivers but did not reveal a latitudinal cline. Previous sampling programs underestimated the abundance of cisco in the Little Whale River. In addition, cisco was the third most abundant species captured in the Povungnituk River, situated 200 km to the north of the previously proposed northern limit at Innuksuac River. As such, the low abundances of cisco in the Great Whale and Innuksuac rivers cannot be attributed to a physiological inability to cope with a reduced growing season. Immature cisco were almost totally absent from the estuaries of the Hudson Bay rivers following spring breakup whereas immature lake whitefish made up 100% of the catch in the Innuksuac River at the same time of year. Species-specific migration patterns in Hudson Bay that differ from those observed in James Bay and the existence of unique juvenile overwintering rivers are 2 hypotheses proposed to explain the discontinuous age-class distribution of cisco and lake whitefish observed in Hudson Bay.Contribution to the program of GIROQ (Groupe Interuniversitaire de Recherche Océanographique du Québec).     

Chlorophyll a biomass and growth of sea-ice microalgae along a salinity gradient (southeastern Hudson Bay,Canadian Arctic)

Summary The biomass of microalgae at the bottom of first-year sea ice, in southeastern Hudson Bay (Canadian Arctic), parallels an inshore-offshore salinity gradient caused by the under-ice plume of the Great Whale River. The present study was designed to test the hypothesis that the variation of ice-algal biomass (chlorophyll a) along the salinity gradient was mainly controlled by nutrient availability, with the alternative hypothesis of a direct control by ambient salinity. The approach was that of differential in situ bioassays, conducted at the ice-water interface of two stations, located in the plume of the Great Whale River (lower salinity) and in the offshore waters of Hudson Bay (higher salinity). The inoculum (collected at the higher salinity station) was diluted with three types of seawater, i.e. (1) from the higher salinity station, (2) from the lower salinity station, and (3) from the latter but with salinity artificially increased to the level of the higher salinity station. The three sets of cultures were differentially enriched. In situ incubations for the first set were at the higher salinity station and, for the other two, at the lower salinity station. Results indicate possible Si limitation of the algal biomass at the higher salinity station. First, concentrations of Si(OH)₄ observed at this station were lower than in the plume of the Great Whale River; in addition, the SiP molar ratios were lower than ca. 15; also, Si was the only nutrient whose addition (alone or combined with others) yielded biomasses higher than in the reference enrichment; finally, the highest growth rate for a singly added nutrient was with Si and subtraction of Si (single nutrient) was more detrimental to growth rate than that of N or P. In contrast, there was no strong indication of nutrient effects at the lower salinity station, so that nutrient limitation could not explain the lower ice-algal biomasses in lower salinity waters. At this same station, on the other hand, growth rates in water with artificially increased salinity were 2–3 times higher than those in unaltered water. These results are consistent with the hypothesis that salinity, and not nutrients, is the main factor that limits the development of ice algae in the lower salinity waters of southeastern Hudson Bay.Contribution to the programs of GIROQ (Groupe interuniversitaire de recherches océanographiques du Québec) and of the Maurice Lamontagne Institute (Biological Oceanography Division, Department of Fisheries and Oceans)     

In situ spectroradiometric estimation of microalgal biomass in first-year sea ice

Summary First- and multi-year sea ice are colonized by microalgae, whose biomass modifies the spectral distribution of underice downwelling irradiance. It is proposed that an index of algal biomass in the first-year ice may be derived from the ratio of underice irradiance at a wavelength where absorption by chlorophyll a is high to a wavelength where absorption by the photosynthetic pigments is low and transmission through the ice is high. In southeastern Hudson Bay (Canadian Arctic), the irradiance ratio (671540 nm) accounts for 55% of the variance in chlorophyll a, indicating that the in situ biomass of algae in first-year ice can be estimated from spectral measurements of underice downwelling irradiance.Contribution to the programme of GIROQ (Groupe interuniversitaire de recherches océanographiques du Québec)     

Schooling behaviour of arctic cod,Boreogadus saida,in relation to drifting pack ice

Synopsis Concentrations of arctic cod were detected with a hydroacoustic system in Resolute Bay, NWT during 2 weeks in August of 1986. Fish biomass within the bay was about 30 t. The fish were feeding primarily on amphipods, which were abundant. When the daily location of the schools was examined in relation to the extent and position of drifting pack ice, a pattern emerged suggesting that the distribution of the fish was influenced by the amount and location of ice cover. If the bay was relatively ice-free, the density of schooling cod was high and the size of the schools, as 2-dimensional surface area, was generally small. When ice covered the bay, density within the schools was lower and they occupied more area. Arctic cod were most dispersed after the bay had been filled with pack ice for several days. It is postulated that this behaviour is a response to potential predation by seabirds and marine mammals.     

Effects of Earlier Sea Ice Breakup on Survival and Population Size of Polar Bears in Western Hudson Bay

ABSTRACT Some of the most pronounced ecological responses to climatic warming are expected to occur in polar marine regions, where temperature increases have been the greatest and sea ice provides a sensitive mechanism by which climatic conditions affect sympagic (i.e., with ice) species. Population-level effects of climatic change, however, remain difficult to quantify. We used a flexible extension of Cormack-Jolly-Seber capture-recapture models to estimate population size and survival for polar bears (Ursus maritimus), one of the most ice-dependent of Arctic marine mammals. We analyzed data for polar bears captured from 1984 to 2004 along the western coast of Hudson Bay and in the community of Churchill, Manitoba, Canada. The Western Hudson Bay polar bear population declined from 1,194 (95% CI = 1,020-1,368) in 1987 to 935 (95% CI = 794-1,076) in 2004. Total apparent survival of prime-adult polar bears (5–19 yr) was stable for females (0.93; 95% CI = 0.91-0.94) and males (0.90; 95% CI = 0.88-0.91). Survival of juvenile, subadult, and senescent-adult polar bears was correlated with spring sea ice breakup date, which was variable among years and occurred approximately 3 weeks earlier in 2004 than in 1984. We propose that this correlation provides evidence for a causal association between earlier sea ice breakup (due to climatic warming) and decreased polar bear survival. It may also explain why Churchill, like other communities along the western coast of Hudson Bay, has experienced an increase in human-polar bear interactions in recent years. Earlier sea ice breakup may have resulted in a larger number of nutritionally stressed polar bears, which are encroaching on human habitations in search of supplemental food. Because western Hudson Bay is near the southern limit of the species' range, our findings may foreshadow the demographic responses and management challenges that more northerly polar bear populations will experience if climatic warming in the Arctic continues as projected.     

Summer Ichthyoplankon in Onega Bay of the White Sea: Species Composition and Spatial Distribution

Data on the species composition and distribution of ichthyoplankton in Onega Bay of the White Sea are presented for June–July 2007, 2010–2012, and 2015–2016. In the ichthyoplankton, the specimens of the early developmental stages of 21 fish species were registered; the larvae of the White Sea herring Clupea pallasi marisalbi, capelin Mallotus villosus, and Pacific sand lance Ammodytes hexapterus were the most abundant. It is shown that the northwestern and southeastern zones, distinguished in Onega Bay by hydrophysical parameters, also differ in species composition and in ichthyoplankton abundance.     

Springtime coupling between ice algal and phytoplankton assemblages in southeastern Hudson Bay,Canadian Arctic

Microalgal assemblages from the bottom ice, the ice-water interface and the water column were systematically sampled from April to June 1986, in southeastern Hudson Bay (Canadian Arctic). The taxonomic similarity between samples from the three environments was assessed using a clustering procedure. There were two groups that comprised samples from both the ice-water interface and the water column, while five other groups were made of samples originating from a single environment. Taxonomic compositions of the two mixed groups suggest two types of connexion between the ice-water interface and the water column, i.e. before the phytoplankton bloom, there was seeding of the water column by ice algae and, during ice melt, interfacial algae contributed to the water column communities that were otherwise typically phytoplankton. Overall, the phytoplankton community underwent a succession from pennate to centric diatoms. Sinking rates of algae from the ice-water interface were estimated using settling columns (SETCOL). The sinking rates increased seasonally (0.4–2.7 m d^–1), which enhanced accessibility of ice-algal cells to the pelagic grazers. Ice algae contributed to water column production as they became accessible to the pelagic grazers, and also by seeding the water column before the phytoplankton bloom.Contribution to the programs of GIROQ (Groupe interuniversitaire de recherches océanographiques du Québec) and of the Maurice Lamontagne Institute (Department of Fisheries and Oceans)     

Gastric evacuation rates and daily rations of Arctic cod (Boreogadus saida) at low temperatures

Gastric evacuation rates were determined for different sizes of Arctic cod (Boreogadus saida) at sub-zero temperatures (−1.4 and −0.5°C). These temperatures represent ambient conditions for Arctic cod in the Canadian high Arctic. Evacuation half-times, the time required for half of the content of the stomach to be evacuated, were longer (36–70 h; mean=51 h) than those reported in studies carried out on other fish species. Gastric evacuation rates at low temperatures were equal to, or below, those predicted by extrapolation from experiments conducted at higher temperatures. There were no significant differences in evacuation rates among fish size-groups or diets, but evacuation rates were slower for fish that had been starved prior to experiments. Estimated daily rations for Arctic cod in Resolute Bay, N.W.T., were 0.51% body weight for small fish (4.5 g) and 1.13% body weight for large fish (51 g). Slow stomach evacuation rates at low temperatures may limit daily food intake when food is seasonally abundant. This may contribute to slow growth rates and limited maximum size of Arctic cod in Canadian high Arctic waters. Received: 14 July 1997 / Accepted: 15 November 1997     

Distinct patterns of Arctic cod (<Emphasis Type="Italic">Boreogadus saida</Emphasis>) presence and absence in a shallow high Arctic embayment,revealed across open-water and ice-covered periods through acoustic telemetry

With climate change resulting in unpredictable sea ice conditions between years, it is crucial to gain a more comprehensive understanding of the subsequent effects on Arctic marine ecosystems. Arctic cod (Boreogadus saida) play a key role in the Arctic marine food web, serving as a food source that is estimated to contribute up to 75 % of energy transfer to higher trophic levels. To investigate Arctic cod residency and distribution in Resolute Bay (74°44′N, 095°04′W), 85 individuals from four locations in the bay were captured, measured, weighed, implanted with acoustic tags and subsequently tracked on an acoustic array of 49 receivers. Two main periods of residence in the bay were identified, the first in open water and the second under ice cover, and both concluded with a collective mass departure of fish. A generalised linear mixed model was used to investigate the influence of variables on Arctic cod presence/absence in the bay, indicating that ingress and egress were influenced by environmental changes, particularly those associated with the transition from open-water to the ice-covered period. Timing and distribution, during the study period, appeared to be influenced by a combination of physiological acclimation, and a balance between resource availability and refuge from predators. Receiver site Residence Index (RI) analysis revealed strong site fidelity of fish towards the northern areas of the bay, and this behaviour was consistent between tagging groups and individuals, indicating that the majority of tagged cod were representative of a single school. This study represents the first employment of acoustic telemetry to monitor the movements of individual Arctic cod over 9 months, incorporating both open-water and ice-covered periods.     

Spawning areas and early development of long spiky-head carp (Luciobrama macrocephalus) in the Yangtze River and Pearl River, China

The spawning areas and early development of long spiky-head carp, Luciobrama macrocephalus (Lacépède), an endemic fish species in China, were investigated in the Yangtze River and Pearl River of central and southeastern China between 1961 and 1993. The potamodromous fish migrated upstream to spawn between May and July as the floodwater began to rise. The water-hardened eggs drifted down the river, and the embryos and larvae developed in the course of drifting. The spawning areas of the fish were widely found in the upper and middle main channels and large tributaries. Two large dams (Gezhouba dam and Danjiangkou dam) did not significantly impact on the reproduction of the fish. Fifty stages of the early development from one cell to the juvenile with fully formed fins were observed and characterized pictorially. The larvae of long spiky-head carp could be distinguished from the larvae of other co-occurring species by counting the number of somites and comparing the proportion of sizes of eye to otic capsule.     

Zooplankton boom and ice amphipod bust below melting sea ice in the Amundsen Gulf, Arctic Canada

Early summer in the Arctic with extensive ice melt and break-up represents a dramatic change for sympagic–pelagic fauna below seasonal sea ice. As part of the International Polar Year-Circumpolar Flaw Lead system study (IPY-CFL), this investigation quantified zooplankton in the meltwater layer below landfast ice and remaining ice fauna below melting ice during June (2008) in Franklin Bay and Darnley Bay, Amundsen Gulf, Canada. The ice was in a state of advanced melt, with fully developed melt ponds. Intense melting resulted in a 0.3- to 0.5-m-thick meltwater layer below the ice, with a strong halocline to the Arctic water below. Zooplankton under the ice, in and below the meltwater layer, was sampled by SCUBA divers. Dense concentrations (max. 1,400 ind. m⁻³) of Calanus glacialis were associated with the meltwater layer, with dominant copepodid stages CIV and CV and high abundance of nauplii. Less abundant species included Pseudocalanus spp., Oithona similis and C. hyperboreus. The copepods were likely feeding on phytoplankton (0.5–2.3 mg Chl-a m⁻³) in the meltwater layer. Ice amphipods were present at low abundance (<10 ind. m⁻²) and wet biomass (<0.2 g m⁻²). Onisimus glacialis and Apherusa glacialis made up 64 and 51% of the total ice faunal abundance in Darnley Bay and Franklin Bay, respectively. During early summer, the autochthonous ice fauna becomes gradually replaced by allochthonous zooplankton, with an abundance boom near the meltwater layer. The ice amphipod bust occurs during late stages of melting and break-up, when their sympagic habitat is diminished then lost.     

Habitat use by harbour seals (Phoca vitulina) in a seasonally ice-covered region, the western Hudson Bay

Over the last few decades, the period of ice cover in Hudson Bay has decreased, owing to climate warming, with breakup occurring approximately 3 weeks earlier than it did 30 years ago. The trend towards lengthening of the open water season has led to speculation that ringed seal numbers would decline, but then harbour seals might become numerous enough to replace ringed seals in the diet of polar bears. The movement patterns of 18 harbour seals equipped with satellite-linked transmitters in the Churchill River estuary (western Hudson Bay) were examined, as well as the dive behaviour of 11 of these seals. During the ice-free period, seals followed a general central place-foraging strategy, making repeated trips between their haul-out site in the Churchill River estuary and nearshore areas (<20 km) near the river mouth and estuary. Seal behaviour changed significantly as ice started to form along the coast of western Hudson Bay: animals remained significantly farther from the Churchill River haul-out site and from the coast and performed longer and deeper dives. However, throughout the entire tracking period, whether ice was present or not, all animals restricted their movements to a narrow band of shallow coastal waters (<50 m depth) along a 600-km stretch of the western Hudson Bay coastline, centred on the Churchill River estuary haul-out site. This natural self-limitation to nearshore shallow waters could restrict the potential for the population to increase in size and replace ringed seals as a primary energy resource for polar bears.     

Under-ice distribution of polar cod <Emphasis Type="Italic">Boreogadus saida</Emphasis> in the central Arctic Ocean and their association with sea-ice habitat properties

In the Arctic Ocean, sea-ice habitats are undergoing rapid environmental change. Polar cod (Boreogadus saida) is the most abundant fish known to reside under the pack-ice. The under-ice distribution, association with sea-ice habitat properties and origins of polar cod in the central Arctic Ocean, however, are largely unknown. During the RV Polarstern expedition ARK XXVII/3 in the Eurasian Basin in 2012, we used for the first time in Arctic waters a Surface and Under Ice Trawl with an integrated bio-environmental sensor array. Polar cod was ubiquitous throughout the Eurasian Basin with a median abundance of 5000 ind. km^?2. The under-ice population consisted of young specimens with a total length between 52 and 140 mm, dominated by 1-year-old fish. Higher fish abundance was associated with thicker ice, higher ice coverage and lower surface salinity, or with higher densities of the ice-amphipod Apherusa glacialis. The fish were in good condition and well fed according to various indices. Back-tracking of the sea-ice indicated that sea-ice sampled in the Amundsen Basin originated from the Laptev Sea coast, while sea-ice sampled in the Nansen Basin originated from the Kara Sea. Assuming that fish were following the ice drift, this suggests that under-ice polar cod distribution in the Eurasian Basin is dependent on the coastal populations where the sea-ice originates. The omnipresence of polar cod in the Eurasian Basin, in a good body condition, suggests that the central Arctic under-ice habitats may constitute a favourable environment for this species survival, a potential vector of genetic exchange and a recruitment source for coastal populations around the Arctic Ocean.     

Biology of Greenland cod,Gadus ogac,at Saqvaqjuac,northwest coast of Hudson Bay

Synopsis The distribution and relative abundance, life history parameters, food habits, and metabolic rate were determined forGadus ogac in Sagvagjuac Inlet, northwest coast of Hudson Bay (63° N). Fish were demersal, non-schooling, and distributed evenly down to 35 m depth. Growth was slow (maximum age 12 y) and mortality relatively low (0.5 y^–1).G. ogac first spawned at 2–3 y and spawned annually thereafter, in late March – early April. They tended to remain in the inlet and were not taken on the open coast. They are top carnivores, taking primarily capelin when available, benthic crustacea (crabs, amphipods) when not. The metabolic rate ofG. ogac is intermediate between the elevated rate of Arctic cod,Boreogadus saida, and eurythermal temperate species. Available data indicate they are not important in marine mammal and bird food webs. Their biology is contrasted with that of Arctic cod, which are short-lived, cryopelagic, feed on pelagic crustacea, and are an extremely important component of Arctic marine food webs.Direct reprint requests     

Global warming triggers the loss of a key Arctic refugium

We document the rapid transformation of one of the Earth''s last remaining Arctic refugia, a change that is being driven by global warming. In stark contrast to the amplified warming observed throughout much of the Arctic, the Hudson Bay Lowlands (HBL) of subarctic Canada has maintained cool temperatures, largely due to the counteracting effects of persistent sea ice. However, since the mid-1990s, climate of the HBL has passed a tipping point, the pace and magnitude of which is exceptional even by Arctic standards, exceeding the range of regional long-term variability. Using high-resolution, palaeolimnological records of algal remains in dated lake sediment cores, we report that, within this short period of intense warming, striking biological changes have occurred in the region''s freshwater ecosystems. The delayed and intense warming in this remote region provides a natural observatory for testing ecosystem resilience under a rapidly changing climate, in the absence of direct anthropogenic influences. The environmental repercussions of this climate change are of global significance, influencing the huge store of carbon in the region''s extensive peatlands, the world''s southern-most polar bear population that depends upon Hudson Bay sea ice and permafrost for survival, and native communities who rely on this landscape for sustenance.     

Growth and Abundance of Pacific Sand Lance, Ammodytes hexapterus, under differing Oceanographic Regimes

Dramatic changes in seabird and marine mammal stocks in the Gulf of Alaska have been linked to shifts in abundance and composition of forage fish stocks over the past 20 years. The relative value (e.g., size and condition of individual fish, abundance) of specific forage fish stocks to predators under temporally changing oceanographic regimes is also expected to vary. We inferred potential temporal responses in abundance, growth, and age structure of a key forage fish, sand lance, by studying across spatially different oceanographic regimes. Marked meso-scale differences in abundance, growth, and mortality existed in conjunction with these differing regimes. Growth rate within stocks (between years) was positively correlated with temperature. However, this relationship did not exist among stocks (locations) and differing growth rates were better correlated to marine productivity. Sand lance were least abundant and grew slowest at the warmest site (Chisik Island), an area of limited habitat and low food abundance. Abundance and growth of juvenile sand lance was highest at the coolest site (Barren Islands), an area of highly productive upwelled waters. Sand lance at two sites located oceanographically between the Barren Islands and Chisik Island (inner- and outer-Kachemak Bay) displayed correspondingly intermediate abundance and growth. Resident predators at these sites are presented with markedly different numbers and quality of this key prey species. Our results suggest that at the decadal scale, Gulf of Alaska forage fish such as sand lance are probably more profoundly affected by changes in abundance and quality of their planktonic food, than by temperature alone.     

Mariculture of kurosoi,Sebastes schlegeli

Synopsis The technology of collecting developing larvae from female kurosoiSebastes schlegeli, and raising the larvae to juveniles (100 mm total length (TL)) to be released into the oopen sea, is presented. Gravid females 40–46 cm TL were captured in May–June 1977–1980 and held in the laboratory until parturition. Fecundity of fish in this size range was 100 000–184 000. Larvae were sequentially fed rotifers,Artemia nauplii, and young sand lance,Ammodytes personatus, until reaching 25 mm; this required 35 days and yielded a survival rate of 50%. Thereafter, the fish were reared in separate size groups to avoid cannibalism. Minced or chopped sand lance and commercial food were provided until the final size of 100 mm was attained. The growth of juvenile kurosoi from 25 to 100 mm required 85 days, with a survival rate of 90%. The effect of released cultured fish on the local stock is being determined from information on the recapture of tagged fish.     

Diet and Habitat use by Bluefish, Pomatomus Saltatrix, in a Chesapeake Bay Estuary

Bluefish, Pomatomus saltatrix, are recreationally valuable finfish along the Atlantic seaboard and in the Chesapeake Bay. Diet and habitat use patterns for bluefish life history intervals in Chesapeake Bay estuaries are poorly described although it is widely acknowledged that this apex piscivorous species relies on estuarine habitat for feeding and nursery grounds after oceanic spawning and inshore migration of larvae. Bluefish diet, distribution, and abundance patterns were examined in relation to oyster reef, oyster bar, and sand bottom habitat in the Piankatank River, Virginia. Bluefish from all sites were predominantly piscivorous and were more abundant at reef sites than non-reef sites. Bluefish caught in association with the oyster reef consumed a wider diversity of prey items than fish from other sites; diet diversity may contribute to bluefish success during periods when small pelagic food fish abundance is reduced. Bluefish estuarine habitat use is positively correlated with the presence of oyster shell habitat and the complex trophic communities centering on oyster reefs.     

Beluga whale ecology: a concern of freshwater biologists?

SUMMARY. 1. Churchill estuary beluga whales displayed their highest densities in freshwater habitat, suggesting preferential use.
2. Whale densities in freshwater were as high as 350 animals km⁻² and represented over one tenth of the estimated Hudson Bay population.
3. Future environmental assessments of hydroelectric development in northern Manitoba, Canada, must consider the effects on the beluga whales.     

Laboratory rearing of wild Arctic cod Boreogadus saida from egg to adulthood

The techniques and protocols used to successfully capture, transport and breed Arctic cod Boreogadus saida, as well as to rear their larvae through to adulthood are summarized. Breeding B. saida will increase the opportunity to study this fish species, which is a critical part of the Arctic food web.