American plaice (Hippoglossoides platessoides) is a flatfish species that has a wide distribution throughout the North Atlantic. Variability in age and size at maturity was examined for cohorts of American plaice from the early 1960s to early 1990s for the three main stocks off the coast of Newfoundland, Canada. Large changes in age and size at maturity have occurred among cohorts since the 1960s, with males and females of all three stocks maturing at an earlier age and smaller size in the latter part of the time period. Maturation was most closely related to total population abundance over the life of a cohort, with cohorts maturing at an earlier age and smaller size when population size was low. Cohorts which experienced higher temperatures appeared to mature earlier and smaller as did cohorts which experienced increased juvenile growth and increased adult mortality.

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We investigated the magnitude of short-term variations in the flux of several species of fish larvae in Conception Bay, Newfoundland, determined the contribution of these fluxes to changes in the abundance of these species, and assessed the factors that may be causing the variations in these fluxes. The net effect of transport ranged from a daily influx of 5.8% to a daily efflux of 6.2% from the population. Short-term variations in transport were associated with variations in wind stress. The contribution of transport to variations in population abundance ranged from 12 to more than 75% of the average daily rate of change in numbers for the different species. The contribution of physical processes to estimated mortality rates is variable and can have a significant impact on the investigation and interpretation of potential biological processes (e.g., predation and starvation) influencing the survival of larval fish. We predicted that the average correction to the instantaneous mortality rate due to advection and diffusion should be proportional to A−1/2, where A is the area of system under study. This highlights the susceptibility of small systems to estimation error of mortality rates caused by short-term variations in physical forcing.

While reasonable knowledge of multi-decadal Arctic freshwater storage variability exists, we have little knowledge of Arctic freshwater exports on similar timescales. A hydrographic time series from the Labrador Shelf, spanning seven decades at annual resolution, is here used to quantify Arctic Ocean freshwater export variability west of Greenland. Output from a high-resolution coupled ice-ocean model is used to establish the representativeness of those hydrographic sections. Clear annual to decadal variability emerges, with high freshwater transports during the 1950s and 1970s–80s, and low transports in the 1960s, and from the mid-1990s to 2016, with typical amplitudes of 30 mSv (1 Sv = 106 m3 s-1). The variability in both the transports and cumulative volumes correlates well both with Arctic and North Atlantic freshwater storage changes on the same timescale. We refer to the "inshore branch" of the Labrador Current as the Labrador Coastal Current, because it is a dynamically- and geographically-distinct feature. It originates as the Hudson Bay outflow, and preserves variability from river runoff into the Hudson Bay catchment. We find a need for parallel, long-term freshwater transport measurements from Fram and Davis Straits, to better understand Arctic freshwater export control mechanisms and partitioning of variability between routes west and east of Greenland, and a need for better knowledge and understanding of year-round (solid and liquid) freshwater fluxes on the Labrador shelf. Our results have implications for wider, coherent atmospheric control on freshwater fluxes and content across the Arctic and northern North Atlantic Oceans.

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.

Bitter crab disease (BCD) is caused by Hematodinium sp., an endoparasitic dinoflagellate. It lives within the hemocoeloms of snow crabs Chionoecetes opilio and Tanner crabs C. bairdi, making them unmarketable due to their bitter flavor. Two recent outbreaks of BCD have occurred in Conception Bay, Newfoundland, one from 1999 to 2000 and another from 2003 to 2005. In the earlier outbreak, prevalence was highest in juvenile and primiparous females and juvenile males. It was thought to be highest in these hosts because they molt more frequently than larger males and the disease is transmitted to newly molted crabs. In the 2003 to 2005 outbreak, the prevalence of BCD changed and was at its highest, 24% in trapped males and 13.5% in trawled males. This apparent shift in the dynamics of the infection between the earlier 1999 to 2000 and later 2003 to 2005 outbreaks was highly correlated with 2 factors: an increase in bottom temperatures, associated with the recent climatic warming trend in the Northwest Atlantic, and an increase in molting activity of the snow crabs due presumably to the temperature increase within Conception Bay. That is, rising temperatures occurring from 2003 to 2005 likely stimulated molting activity in snow crabs, which led to an increase in susceptible hosts in the population. Given the positive correlation between increased bottom temperature, increased molting activity, and the latest outbreak of BCD, we predict that further trends in climatic warming will enhance transmission, spreading the parasite into additional fishing areas.

Meteorological and ice data from the Atlantic region indicate that the large-scale atmospheric circulation over the Northwest Atlantic during the early 1990s caused below-normal air temperatures in eastern Canada, resulting in increased ice growth during winter, increased ice transport from northern latitudes, and increased freshwater from melting ice during spring. The reduced solar flux onto the ocean surface resulted in a 3-to 4-wk delay in the annual warming cycle causing record low temperatures over the upper water column throughout the Newfoundland Shelf region. We examined temperature, salinity, and current measurements from acoustic Doppler current profilers, moored current meters, and drogued drifting buoys to establish the hydrographic conditions and circulation on the Newfoundland Shelf during 1990-1993 in relation to the longer term (1950-1989) mean. The mean circulation and transport do not show significant departures from the long-term average, but the total advective summer heat transport through the Bonavista transect indicates a 26% reduction during the early 1990s. Résumé : Les données relatives aux conditions météorologiques et à la couverture de glace pour la région de l'Atlantique indiquent que la circulation atmosphérique à grande échelle au-dessus de l'Atlantique Nord-Ouest dans les premières années de la présente décennie a causé, dans l'Est du Canada, des températures de l'air inférieures à la normale, ce qui a entraîné une augmentation de l'englacement durant l'hiver, un accroissement du transport de glace à partir des latitudes nordiques, et une augmentation de la quantité d'eau douce provenant de la fonte des glaces au printemps. La réduction du flux solaire atteignant la surface de l'océan a entraîné un retard de 3 à 4 sem dans le cycle annuel de réchauffement, ce qui a occasionné des records de basse température de l'eau de surface, dans toute la région de la plate-forme de Terre-Neuve. Nous avons étudié les mesures de la température, de la salinité et des courants obtenues grâce à des profileurs de courant acoustiques Doppler, à des courantomètres mouillés et à des bouées dérivantes équipées de drogues, afin de déterminer les conditions hydrographiques et la circulation sur la plate-forme de Terre-Neuve au cours des années 1990-1993 par rapport aux valeurs moyennes établies sur de plus longues périodes (1950-1989). Les moyennes pour la circulation et le transport ne montrent pas d'écarts significatifs par rapport à la moyenne sur 49 ans; par contre, le transport total de chaleur par advection en été sur la section de Bonavista indique une réduction de 26% au début des années 90.

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