Newfoundland Continental Shelf Research Articles

Seasonal and depth-dependent variations in the size and lipid contents of stage 5 copepodites of Calanus finmarchicus in the waters of the Newfoundland Shelf and the Labrador Sea

We report on the variation in energy reserves of individual C5 copepodites of Calanus finmarchicus from the Newfoundland continental shelf and the Labrador Sea collected from surface and overwintering (or bottom) depths prior to, during and after the expected timing of the onset of diapause. Overall, the trend was for a decreasing average prosome length as the year progressed for all locations although the decline was smallest in the Labrador Sea and greatest in the deep waters of the continental shelf. The size of the oil sac was closely linked to the weight of the copepodite but the form of this relationship showed substantial variations with depth and season. We show a clear increase in the relative oil sac volume for C. finmarchicus between late spring and late summer, by which time some animals had descended to diapause depths. The progressive decrease in oil sac volume of animals sampled at depth in the Labrador Sea between September and December suggests a significant loss of energy reserves during diapause. From the distribution of volumes and body sizes in December we estimate that 23–53% of individuals would not be able to meet the energetic cost of moulting and early gonad development. Overall, some of our observations appear to invalidate earlier hypotheses concerning the governing role of lipids in the life history of C. finmarchicus. However, assessment of the factors that influence entry into dormancy should be based on the relative probabilities of alternative strategies for successful reproduction (e.g. entering dormancy vs. continuing into a second generation).

Variability of the Stratification and Circulation on the Flemish Cap duringthe decades of the 1950s-1990s

Oceanographic observations on the Flemish Cap (around 47°N, 45°W) from the early-1990s to 1999 are compared to the long-term mean and to conditions during the past several decades. The mean temperature and salinity fields and their seasonal cycles were first computed and then used to construct T/S anomaly time series. The data shows a relatively warm time period from the 1950s through the 1960s and three colder-than-normal periods since the early-1970s. In general, it was found that variations in water properties on the Flemish Cap are highly correlated with those observed in the inshore branch of the Labrador Current at Station 27 and in other areas of the Newfoundland Continental Shelf. Studies have shown that these conditions are linked to the largescale atmospheric winter circulation, sea ice conditions, local atmospheric forcing and advection. An examination of local air-sea heat flux indicate that advection of Labrador Current water into the region may be the principle cause of oceanic variability over the Flemish Cap. An examination of recent acoustic Doppler current measurements and geostrophic current calculations indicated the predominance of an anticyclonic gyre circulation around the Flemish Cap during the summer and a significant and persistent Labrador Current component to the circulation. The results, however, exhibited a high degree of interannual variability.

Predominance of squid ( Gonatus spp.) in the diet of Greenland halibut ( Reinhardtius hippoglossoides) on the deep slope of the northeast Newfoundland continental shelf

The feeding ecology of Greenland halibut ( Reinhardtius hippoglossoides) on the deep slope of the northeast Newfoundland continental shelf was investigated based on stomach analysis. Stomach samples were collected from the spring 1992 Canadian bottom trawl fishery at depths of 1000–1250 m. The squid, Gonatus spp., predominated in the diet, representing the first known instance of reliance of Greenland halibut upon this bathypelagic squid as prey in Canadian waters. A change from predation primarily upon pelagic prey, reported in earlier studies, may be related to annual variability in abundance and distribution of both Greenland halibut and its principal pelagic fish prey species, capelin ( Mallotus villosus). Seasonal effects may account for the absence of epipelagic, juvenile Gonatus spp. from the diet. There was a linear size relationship in observed predation which may reflect a common size-related depth distribution pattern between predator and prey or, more likely, prey selectivity. At larger sizes, Greenland halibut switched from Gonatus spp. to groundfish as its principal prey. The importance of Gonatus spp. in the deep continental slope trophic web is reviewed.

Mitochondrial DNA sequence variation and genetic stock structure of Atlantic cod (Gadus morhua) from bay and offshore locations on the Newfoundland continental shelf.

Bay cod, Atlantic cod (Gadus morhua) that over-winter in the deep-water bays of north-eastern Newfoundland, have historically been regarded as distinct in migration and spawning behaviour from offshore (Grand Bank) cod stocks. To investigate their genetic relationships, we determined the DNA sequence of a 307-base-pair portion of the mitochondrial cytochrome b gene for 236 adult cod taken from the waters off north-eastern Newfoundland, including fish found over-wintering and spawning in Trinity Bay. Although 17 genotypes were found, a single common genotype occurs at a frequency of greater than 80% in all samples, and no alternative genotype occurs at a frequency of greater than 3%. Genotype proportions did not differ significantly among samples. Measures of genetic subdivision among sampling locations are nil. Cod over-wintering in Trinity Bay are not genetically distinct from offshore cod. In combination with tagging and physiological studies, these data suggest that there is sufficient movement of cod between bay and offshore locations to prevent the development or maintenance of independent inshore stocks. Adult cod that over-winter in Trinity Bay appear to represent an assemblage of temporarily nonmigratory fish that have become physiologically acclimated to cold-water inshore environments. The pattern of genetic variation in northern cod suggests a recent population structure characterized by extensive movement of contemporary individuals superimposed on an older structure characterized by a bottleneck in the population size of cod in the north-western Atlantic.

Investigating the marginal ice zone on the Newfoundland Shelf

From the ice and current data collected over the Newfoundland Shelf by the second Canadian Atlantic Storms Program (CASP II), it is evident that ice motion is affected by wind‐generated ocean current. This points to the importance of coupled ice‐ocean response to wind forcing in the study of shortterm ice motion and operational ice forecasting. The mutual influence of ice and the ocean can also be seen in the water properties.To study the mature stages of explosive cyclogenesis in east coast winter storms and to investigate their influence on the circulation and sea ice properties on the Newfoundland continental shelf and Grand Banks, CASP II was conducted by scientists from the Bedford Institute of Oceanography (BIO), the Atmospheric Environment Service (AES), the National Research Council (NRC), and many universities, private companies, and other government agencies.

Response of sea ice drift to wind forcing on the northeastern Newfoundland Shelf

Observations of sea ice drift obtained with satellite‐tracked ice beacons in March–April of 1988 and 1989 have been used to examine the response of sea ice drift to wind forcing over the northern Newfoundland continental shelf. The short‐term (5–20 days) response of sea ice drift ranges from 2.6 to 5.4% of the local wind over much of the inner continental shelf, which is comparable to that in the Bering Sea and the Antarctic but larger than that in Arctic. Sea ice drifts to the right of the local wind, at angles ranging from 10° to 63°. The response to wind forcing is largest near the ice edge, both over the middle portions of the shelf and along the southern margins of the seasonal ice zone and during strong and steady wind of several days' duration. The large wind‐driven response of ice drift observed in this study, in comparison with the Arctic, may result from (1) reduced levels of internal ice stress associated with the generally thin ice cover and lower areal concentration of sea ice, (2) large atmospheric drag coefficients associated with the small ice floes in areas of comparatively higher ice concentration, and (3) smooth ice bottom caused by melting. In nearshore areas the ice to wind coupling is reduced owing to larger internal ice stresses experienced locally due to ice pileup.

The influence of Hudson Bay runoff and ice‐melt on the salinity of the inner Newfoundland Shelf

Abstract The present study examines sources of the interannual variability in salinity on the Newfoundland continental shelf observed in a 40‐year time series from an oceanographic station known as Station 27. Specifically, we investigate, through lag‐correlation analysis, the a priori hypotheses that the salinity anomalies at Station 27 are determined by freshwater runoff anomalies from Hudson and Ungava bays and by ice‐melt anomalies in Hudson Bay and on the Labrador Shelf. Interannual variations of summer runoff into Hudson Bay were significantly negatively correlated with salinity anomalies on the Newfoundland Shelf with a lag (9 months) that is consistent with expected travel times based on known current velocities in Hudson Bay and along the Labrador Shelf. Sea‐ice extent over the Labrador and northern Newfoundland shelves was significantly negatively correlated with salinity at a lag of 3 to 4 months, corresponding to the time of minimum salinity at Station 27. It appears that ice‐melt over the Lab...

The Newfoundland continental shelf dispute in the Supreme Court of Canada

The Newfoundland continental shelf dispute in the Supreme Court of Canada

Circulation on the newfoundland continental shelf

Abstract The circulation on the Newfoundland Continental Shelf derived from a review of different data sources generally agrees with the classical description of the flow in this area given by Smith et al. (1937). Hydrological, surface and bottom drifter, satellite‐tracked buoy, ships drift, current meter and sea‐level observations are used to estimate mean flows, transports, and fluctuating currents and to define the circulation pattern on the shelf and slope. The review suggests several aspects of the oceanography and dynamics of the Newfoundland Continental Shelf that merit further attention.

Frosted Beach-Sand Grains on the Newfoundland Continental Shelf

Frosted, relict beach sands in 90 m of water on part of the Newfoundland continental shelf have been identified by analysis of grain-size frequency distributions and surface textures. In this case, the common interpretation that frosted sands on the Atlantic continental shelf are indicative of aeolian deposition during periods of Pleistocene eustatic lowering of sea level would be incorrect. The results suggest that combined grain-size frequency distribution analysis and grain-surface texture analysis with a scanning electron microscope are probably necessary to properly evaluate the depositional environment of frosted grains.

Glauconite in Surficial Sediments as an Indicator of Underlying Cretaceous/Tertiary Bedrock on the Northeast Newfoundland Continental Shelf

Glauconite in surficial sediment from part of the northeast Newfoundland continental shelf is similar in internal structure, external morphology, and abundance to glauconite in a probable Cretaceous or Tertiary subarkose dredged from the same area. This suggests: (1) the glauconite in surficial sediment is derived from the subarkose and/or possibly other glauconite-bearing rocks, (2) the subarkose is one lithology underlying the outer northeast Newfoundland shelf, and (3) the distribution of glauconite in surficial sediments may be used to 'map' underlying bedrock on the northeast Newfoundland shelf.