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The impacts of climate change on marine ecosystems can be seen in the changing distribution, migration, and abundance of species in the oceans. For some species this changing environment may be beneficial and can support population expansions. In the northeast Atlantic (NEA), the Atlantic mackerel (Scomber scombrus) is undergoing an increase in stock size accompanied by changing summer migration patterns, which have resulted in an expansion further north and north west than previously recorded. This study uses microsatellite loci to confirm the differentiation among NEA and northwest Atlantic (NWA) mackerel spawning populations and to assess the level of structuring within these populations. In addition, to enable population-specific exploitation rates to be factored into fisheries management, we identified the origin of individuals composing the expanding feeding aggregations in the central north Atlantic (Greenland, Iceland, Faroes), with all aggregations tested originating from spawning populations in the NEA. This study showed that microsatellite loci were useful to assess the contribution of NEA and NWA populations to mixed feeding aggregations across the north Atlantic for large pelagic fish stocks but were not powerful enough to evaluate the specific contribution of known stocks within NEA and NWA.

Carbon anode blocks used in the Hall-Heroult process for primary aluminum production have to be baked up to 1100 °C in dedicated furnaces. These furnaces are equipped with burner ramps to heat the air circulating in the flues at 1200 °C, so that the anodes reach the required temperature. It is therefore mandatory to include the heat provided by the burners in a numerical model of an anode baking furnace. In this work, we modeled the heat input at the burners in three ways: the Eddy-Dissipation model, the Mixture Fraction/PDF approach and a simplified approach consisting in injecting an equivalent calorific value at the burners' inlets. Results obtained with the first two models are very similar in terms of anode baking prediction but slightly different in terms of flame temperature prediction. Results obtained with the simplified approach show that the model can replace combustion model to predict anode baking, but calibration of boundary conditions is necessary in order to match more elaborate combustion models. The importance of other elements of the model in the flue channel of the furnace has been verified: radiation (cannot be ignored, large influence on the spatial temperature distribution), heat transfer due to species diffusion (negligible influence on the baking, but slight effect on flame shape and temperature), and buoyancy (no significant effect on the results in the furnace firing sections).

Depuis plusieurs annees, le concept d’approche ecosystemique est avance mondialement comme une solution possible aux problematiques de gestion liees a la deterioration des ecosystemes marins et de ...

The objective of this study was to assess the effect of environmental variability on the dynamics of the Atlantic mackerel (Scomber scombrus L.) stock in the Gulf of St. Lawrence (GSL). We first described the dominant modes of physical and biological (zooplankton) variability using Principal Components Analyses of 40 variables. Two principal modes of variability were identified, a long-term mode (15–20 yr) associated with a warming of the GSL and a second mode describing alternating cold and warm periods at a higher frequency (5–10 yr). A strong link between physical forcing and the dynamics of zooplankton species known to be important for mackerel was shown. Second, a set of Generalized Additive Models (GAM) was developed to explore how these environmental variations could influence mackerel condition (Fulton’s K) and recruitment success (Rs). Optimal GAMs including variations in abundance, species composition and phenology of key copepods improved model performance by 40–50% relative to those considering only physical environmental conditions. The results are consistent with the match–mismatch hypothesis and illustrate the key role of zooplankton dynamics in modulating variations in mackerel K and Rs. Finally, this study showed that large variations in Rs could be caused by varying environmental conditions independently of the influence of stock biomass. Our results strongly indicate that the effect of environmental variability should be considered in the implementation of an ecosystem-based approach to Atlantic mackerel stock management.

Reproductive success of seabirds is tightly associated with availability of their prey for which the spatiotemporal distribution may be influenced by sea surface temperature (SST) fluctuations. The objective of this study was to investigate whether Northern gannets (Morus bassanus) from the largest colony in North America (Bonaventure Island, Quebec, Canada) were in negative nutritional state during the unprecedented low reproductive success year of 2012, and whether this was associated with changes in SST anomalies and diet. The incubation period of gannets in 2012 was characterized by a significant decline, from early to late incubation, in plasma triglyceride levels that was associated with an increase in plasma corticosterone levels. However, no changes in plasma glycerol and β-hydroxybutyrate levels were noted. SST anomalies recorded in this area (south of the Gulf of St. Lawrence) during the breeding period were consistently higher in 2012 compared to the previous year (a better reproductive success year). Based on signatures of stable carbon (δ(13)C) and nitrogen (δ(15)N) isotopes in gannet red blood cells and in whole fish homogenates of three major preys (mackerel, herring, and capelin), a minor dietary shift was noted between those years and incubation periods. In light of these findings, it is suggested that the extreme warm-water perturbation event that prevailed in the Gulf of St. Lawrence during summer 2012 was associated with a rapid deterioration of nutritional condition of Bonaventure Island gannets during the incubation. These suboptimal physiological changes likely contributed to the dramatic decline in reproductive success reported in this colony.

This paper reviews the current knowledge on the ecology of widely distributed pelagic fish stocks in the North Atlantic basin with emphasis on their role in the food web and the factors determining their relationship with the environment. We consider herring (Clupea harengus), mackerel (Scomber scombrus), capelin (Mallotus villosus), blue whiting (Micromesistius poutassou), and horse mackerel (Trachurus trachurus), which have distributions extending beyond the continental shelf and predominantly occur on both sides of the North Atlantic. We also include albacore (Thunnus alalunga), bluefin tuna (Thunnus thynnus), swordfish (Xiphias gladius), and blue marlin (Makaira nigricans), which, by contrast, show large-scale migrations at the basin scale. We focus on the links between life history processes and the environment, horizontal and vertical distribution, spatial structure and trophic role. Many of these species carry out extensive migrations from spawning grounds to nursery and feeding areas. Large oceanographic features such as the North Atlantic subpolar gyre play an important role in determining spatial distributions and driving variations in stock size. Given the large biomasses of especially the smaller species considered here, these stocks can exert significant top-down pressures on the food web and are important in supporting higher trophic levels. The review reveals commonalities and differences between the ecology of widely distributed pelagic fish in the NE and NW Atlantic basins, identifies knowledge gaps and modelling needs that the EURO-BASIN project attempts to address.

Atrial fibrillation is a disorganization of the electrical propagation in the atria often initiated by ectopic beats. This spontaneous activity might be associated with the appearance of sustained oscillations in some portion of the tissue. Adrenergic stress and specific gene polymorphisms known to promote atrial fibrillation are notably related to calcium and potassium channel conductances. We performed codimension-one and two bifurcation analysis along these conductances in an ionic canine atrial myocyte model. Two Hopf bifurcations were found, related to two distinct mechanisms: (1) a fast calcium gating-driven oscillator, and (2) a slow concentration-driven oscillator. These two mechanisms interact through a double Hopf bifurcation (HH) in a neighborhood of which a torus (Neimark–Sacker) bifurcation leads to bursting. A complex codimension-two theoretical scenario was identified around HH, through systematic comparison with the attractors found numerically. The concentration oscillator was further decomposed to reveal the minimal oscillating subnetwork, in which the Na + /Ca 2+ exchanger plays a prominent role.

Predators utilize a variety of behavioral techniques to capture elusive prey. Behavioral flexibility is essential among generalist predators that pursue a diversity of prey types, and capture efficiency is expected to be intense during the breeding season for parents that engage in self- and offspring-provisioning. We studied the foraging behavior of parental northern gannets in the northwestern Atlantic (Gulf of St. Lawrence) when they were feeding on Atlantic mackerel almost exclusively. Data-loggers recorded short (mean duration: 6.3 s), high speed (inferred vertical speeds of up to 54.0 m*s− 1, equivalent to 194 km*h− 1), and shallow dives (mean depth: 4.2 m; maximum: 9.2 m). Dives tended to occur in bouts, varying between 0.3 and 4.6 per hour (mean = 1.6). During foraging, overall flight heights ranged from 0 to 70 m, with no clear preferences for height. Most plunge-dives were initiated at flight altitudes of 11–60 m (mean ± SE = 37.1 ± 2.8 m; range 3–105 m except for 1 of 162 dives that was initiated at the sea surface). Dive depth and flight altitude at plunge-dive initiation were positively and significantly correlated, though it appears that low flight altitudes were sufficient to reach dive depths at which mackerel were present. Almost all dives were V-shaped indicating that a high acceleration attack is the most effective strategy for gannets feeding on large rapid-swimming prey such as mackerel that owing to thermal preferences does not occur below the thermocline and are thus well available and essentially trapped in the water depths exploited by northern gannets.

Carbon anode blocks, used in aluminum electrolysis cells, are usually baked in furnaces for several days, during which they release volatiles due to pitch pyrolysis. Therefore, numerical modeling o...

A previous study identified relationships linking variations in the physical environment to fluctuations in zooplankton biomass and Atlantic mackerel (Scomber scombrus) recruitment. Diets of mackerel larvae were compared among four years, one of these years producing an exceptional year-class (1982). Comparisons were standardized for larval length and time of day. Stomach fullness differed significantly among years, with highest values observed in 1982. Stomach content wet weights were significantly larger in 1982 than in 1987 and 1996. The mean weight of Calanus finmarchicus nauplii prey in the diet was also significantly greater in 1982 than in 1985, 1987, or 1996. Female C. finmarchicus were more abundant and more widely distributed in the southern Gulf of St. Lawrence in 1982 compared with 1985, 1987, and 1990. These findings are consistent with the hypothesis of a link between production of copepod nauplii, feeding of mackerel larvae, and recruitment success. However, mackerel size at the end of the first year, as measured on otoliths, varied significantly between years and was smallest in 1982. We propose hypotheses to account for the coupling between high larval food abundance, small juvenile growth, and strong cohorts.

Atlantic mackerel Scomber scombrus are known to be lethal vectors of paralytic shellfish poisoning (PSP) toxins to predators. To elucidate dynamics of PSP toxin accumulation in this species, mackerel were sampled in the Gulf of St Lawrence from May to October 1993. Mackerel appear to retain toxins (saxitoxin, gonyautoxins 2 and 3) year-round. The toxin content of the liver, as determined by high performance liquid chromatography, increased significantly with fish age (r2=0.40) and length (r2=0.52), suggesting that mackerel progressively accumulate PSP toxins throughout their life. The toxin content of the liver also increased significantly during the summer feeding sojourn in the Gulf of St Lawrence. Comparison of profiles of saxitoxin derivatives indicated that zooplankton were the likely source of PSP toxins found in mackerel. The mean ± S.D toxin content was 17.4 ± 10.6 nmol liver−1 and the mean ± S.D. PSP toxicity was 112.4 ± 67.0 μg saxitoxin equivalents 100 g−1 liver wet weight (n=247).

Observations about the cold spell of January-February 1985 in the Cessieres region (Aisne). The cold spell of January-February 1 985 has been recorded at the scale of the botanical site thanks to the existence of a permanent equipment of mesological measures established in the typical biocoenoses of the Cessieres region (Aisne). Some observations have been done on spontaneous species : they have shown that the effects of the cold weather have affected some plants of the subatlantic serie (Ulex europaeus) except others ones (Erica tetralix)., La vague de froid de janvier et février 1985 a pu être enregistrée à l'échelle de la station botanique grâce à l'existence permanente d'un dispositif de mesures mésologiques implanté dans des biocénoses typiques de la région de Cessières (Aisne). Des observations faites sur des espèces spontanées, il apparaît que les effets du froid ont atteint certaines plantes du cortège subatlantique (Ulex europaeus) à l'exception d'autres (Erica tetralix)., Bock C., Grégoire François. Observations sur la vague de froid de janvier-février 1985 dans la région de Cessières (Aisne).. In: Hommes et Terres du Nord, 1986/4. Milieux tempérés humides. pp. 262-270.

Gregoire Francois. Le dernier defenseur des tourbillons : Fontenelle.. In: Revue d'histoire des sciences et de leurs applications, tome 7, n°3, 1954. pp. 220-246.

L’abondance du saumon atlantique (Salmo salar) dans le nord de l’Atlantique a diminué considérablement au cours des dernières décennies. Jusqu’à maintenant, peu de stocks ont montré des signes de rétablissement malgré des efforts importants pour renverser cette situation. Les niveaux décroissants d’abondance des saumons adultes de retour en rivière pourraient être associés à une augmentation de la mortalité naturelle en mer découlant d’une réduction de la croissance. La présente étude a pour but de vérifier si 2 indices de croissance scalaire en phase marine (la distance intercirculi maximale atteinte lors de la première saison estivale en mer et la somme des distances intercirculi de la zone de croissance marine des écailles) et l’abondance des retours de saumon dans la rivière Matane (Québec, Canada) appuient cette hypothèse. Bien que ces indices présentent des différences interannuelles significatives, ils affichent une tendance à la hausse de 1964 à 1979 et une tendance à la baisse de 1995 à 2012. Ces tendances sont semblables à celles des retours de saumons adultes en rivière et à celles de l’indice de l’oscillation nord-atlantique (IONA). Ces similitudes concordent avec l’hypothèse d’une relation inverse entre la croissance marine et la mortalité et, conséquemment, les variations d’abondance qui en résultent., The abundance of Atlantic salmon (Salmo salar) in the North Atlantic has declined significantly in recent decades. Despite substantial efforts to reverse this trend, few stocks have shown signs of recovery. The decreasing number of adult salmon returning to rivers may be due to an increase in natural marine mortality linked to a reduction in growth. The present study aimed to verify whether this hypothesis was supported by two marine phase scalar growth indices (the maximum intercirculi distance attained during the first summer at sea and the total intercirculi distance of the marine growth zone) and the abundance of salmon returning to the Matane River (Québec, Canada). Although the two indices show significant interannual differences, they show an upward trend from 1964 to 1979 and a downward trend from 1995 to 2012. These trends are similar to those of river returns by adult salmon and to the North Atlantic Oscillation Index (NAOI). These similarities support the hypothesis of an inverse relationship between marine growth and mortality, which would subsequently result in variations in abundance.