Modeling the depuration potential of blue mussels (Mytilus spp.) in response to thermal shock

When contaminated, most molluscs destined for human consumption require a depuration regime lasting 48 h at a minimum temperature of 5 °C to ensure elimination of coliforms. However, this regime is unsatisfactory in northern temperate regions, where temperatures are frequently below 5 °C. A series of tests were undertaken to determine the filtration activity of mussels (Mytilus spp.) under cold temperatures. We used physiological measures rather than the more traditional method of bacterial analysis to evaluate mussel acclimation to cold temperatures. Mussels were acclimated for 4 weeks at three different temperatures (8, 4, and − 1 °C) and their scope for growth was evaluated each week to determine the level of acclimation. Mussels were then exposed to a thermal shock and clearance rates were measured after 2 h and 72 h. We observed a clearance rate of 2.45 l h− 1 g− 1 (g DW) for the 8 °C control group. Thus, within a 48-h depuration period, Mytilus spp. could filter a standard volume of 117.47 l. We used a von Bertalanffy exponential model to estimate the time required for an individual from each thermal shock treatment to filter that standard volume. We found that thermal shock had an important effect on the volume filtered by a mussel in 48 h. For example, mussels acclimated at 8 °C were able to filter the standard volume of 117.47 l in an average of 75 h at 4 °C, whereas those acclimated at 4 °C and transferred to 8 °C required only 23 h on average

Fluctuating asymmetry and mortality in cultured oysters (

Japanese cupped oysters suffer summer mortality in many culture sites along the French Atlantic coast. To ascertain whether mortality might be associated with morphological features of the shells, we estimated fluctuating asymmetry (FA) of hatchery/nursery-produced oysters kept in culture bags in the intertidal. FA is defined as random variations from a perfect symmetry plane (bilateral or radial) in some morphological trait. FA increases with disruption of homeostasy during ontogeny and has both genetic and environmental determinants. We found significant differences in FA between dead and live oysters in two of our three study groups. Therefore, lack of developmental stability may be involved in the summer mortality syndrome of oysters. We also found indirect evidence that once acquired, FA patterns of shells are retained at least partially. Since FA likely appears early during ontogeny and is recorded in the shells, we hypothesise that it might be useful for forecasting the ability of spat to resist environmental stress

Body size, population density and factors regulating suspension-cultured blue mussel (

We sampled 27 month-old mussel populations grown on collector ropes in Cascapédia Bay, Quebec, to test whether density-dependent growth was present concomitantly to self-thinning, a process which was previously shown to occur in this system and thought to be driven by spatial constraints. Biomass-density curves of raw samples were curvilinear, suggesting density-dependent growth. However, at least two cohorts were present. Fractionating the samples on the basis of age yielded a linear relationship for the main, 2 year-old cohort. This implies density-independent growth and rules out food regulation in these populations. Therefore, our results are consistent with inferences drawn previously from the values of the self-thinning exponent, that is, space-regulated self-thinning. Our results suggest that curvilinearity of the raw biomass-density curves resulted from a bias caused by including the 1 year-old cohort and spat of the year in the analysis. This conclusion is supported by a model showing that samples with mixed cohorts can yield linear, concave or convex biomass-density curves without density-dependent growth. The shape of the curves depends on the scaling relationships between cohort abundances. It appears that the shape of biomass-density curves may be a useful complementary criterion – in addition to the value of self-thinning exponents – for the identification of food or space as factors regulating cultured populations

HABITAT SELECTION BY MOOSE (ALCES ALCES) IN CLEAR-CUT LANDSCAPES

Habitat selection by moose was studied over 4 years in two large sectors subject to intensive forest harvesting using a two-scale approach. At the coarser scale, i.e. location of the home range within the landscape, habitat selection did not appear to be influenced by the presence of clear-cuts. In one sector, moose preferred mature mixed stands, young coniferous, and mature coniferous stands. In the second sector, the highest preference was noted for cut areas and mature deciduous stands. Moose home ranges were located in areas with higher edge and interspersion among habitat patches. Home range size for females was positively related to the proportion of cuts, but movements were not. Habitat selection was more pronounced at the finer scale (animal locations within home range) and did not differ between sectors. Mixed stands were preferred in all seasons. Mature conifer stands were preferred in summer and in early winter while young conifer stands were preferred in late winter. Clear-cuts were avoided except in early winter. Moose were located in areas closer to edge between food and cover stands than were random locations, especially in late winter. A marked decrease in movements also was noted in late winter. This study shows differences in habitat selection pattern between the coarser and finer scales. For example, clear-cuts did not seem to markedly influence home range location at a coarser scale, and adaptations to minimize their impact seemed to operate at a finer scale. Coarser scale habitat selection was probably linked to a trade-off between predator avoidance and browse availability, whereas seasonal changes suggest behavioural adaptations of moose to maximize energy gain and counteract predation and other adverse environmental conditions at the finer scale

A Generalized Lidar-Based Model for Predicting the Merchantable Volume of Balsam Fir of Sites Located along a Bioclimatic Gradient in Quebec, Canada

Lidar-based models rely on an optimal relationship between the field and the lidar data for accurate predictions of forest attributes. This relationship may be altered by the variability in the stand growth conditions or by the temporal discrepancy between the field inventory and the lidar survey. In this study, we used lidar data to predict the timber merchantable volume (MV) of five sites located along a bioclimatic gradient of temperature and elevation. The temporal discrepancies were up to three years. We adjusted a random canopy height coefficient (accounting for the variability amongst sites), and a growth function (accounting for the growth during the temporal discrepancy), to the predictive model. The MV could be predicted with a pseudo-R2 of 0.86 and a residual standard deviation of 24.3 m3 ha−1. The average biases between the field-measured and the predicted MVs were small. The variability of MV predictions was related to the bioclimatic gradient. Fixed-effect models that included a bioclimatic variable provided similar prediction accuracies. This study suggests that the variability amongst sites, the occurrence of a bioclimatic gradient and temporal discrepancies are essential in building a generalized lidar-based model for timber volume

Effect of Yttrium-90 transarterial radioembolization in patients with non-surgical hepatocellular carcinoma: A systematic review and meta-analysis.

BackgroundRecently, the use of Yttrium-90 transarterial radioembolization in non-surgical hepatocellular carcinoma was suggested but the evidence supporting its use is unclear.MethodsWe searched Medline, Embase, Web of Science and Cochrane CENTRAL from inception up to April 14, 2020 for randomized controlled trials comparing Y90-TARE to standard of care in non-surgical HCC patients. Our primary outcome was overall survival (OS). Our secondary outcomes were progression-free survival, time to progression, disease control rate, grade ≥3 adverse events and rates of gastro-intestinal ulcers. Hazard ratios (HR) and risk ratios (RR) with random-effects model were used for our analyses. The risk of bias of the included studies was assessed using Cochrane's RoB 2 tool.ResultsOf 1,604 citations identified, eight studies (1,439 patients) were included in our analysis. No improvement in overall survival were noted when Yttrium-90 transarterial radioembolization was compared to standard treatments (HR 0.99 [95% CI 0.81-1.21], 6 studies, I2 = 77.6%). However, Yttrium-90 transarterial radioembolization was associated with fewer grade ≥3 adverse events (RR 0.64 [95% CI 0.45-0.92], 7 studies, I2 = 66%). No difference was observed on other secondary outcomes.DiscussionIn non-surgical HCC patients, Yttrium-90 transarterial radioembolization was not associated with significant effect on survival, progression-free survival, time to progression, disease control rate and the incidence of gastro-intestinal ulcers but was however associated with significantly lower rates of grade ≥3 adverse events. Further randomized controlled trials are warranted to better delineate optimal treatment

Intraspecific genetic admixture and the morphological diversification of an estuarine fish population complex.

The North-east American Rainbow smelt (Osmerus mordax) is composed of two glacial races first identified through the spatial distribution of two distinct mtDNA lineages. Contemporary breeding populations of smelt in the St. Lawrence estuary comprise contrasting mixtures of both lineages, suggesting that the two races came into secondary contact in this estuary. The overall objective of this study was to assess the role of intraspecific genetic admixture in the morphological diversification of the estuarine rainbow smelt population complex. The morphology of mixed-ancestry populations varied as a function of the relative contribution of the two races to estuarine populations, supporting the hypothesis of genetic admixture. Populations comprising both ancestral mtDNA races did not exhibit intermediate morphologies relative to pure populations but rather exhibited many traits that exceeded the parental trait values, consistent with the hypothesis of transgressive segregation. Evidence for genetic admixture at the level of the nuclear gene pool, however, provided only partial support for this hypothesis. Variation at nuclear AFLP markers revealed clear evidence of the two corresponding mtDNA glacial races. The admixture of the two races at the nuclear level is only pronounced in mixed-ancestry populations dominated by one of the mtDNA lineages, the same populations showing the greatest degree of morphological diversification and population structure. In contrast, mixed-ancestry populations dominated by the alternate mtDNA lineage showed little evidence of introgression of the nuclear genome, little morphological diversification and little contemporary population genetic structure. These results only partially support the hypothesis of transgressive segregation and may be the result of the differential effects of natural selection acting on admixed genomes from different sources

Sample categories, numerical IDs, sample site locations, dates, developmental stages and sample sizes for AFLP and mtDNA analyses of rainbow smelt.

<p>All fish were sampled during 2011–2012. SLR- St. Lawrence River, YOY- young of the year (larval and post metamorphic stages).</p><p>Sample categories, numerical IDs, sample site locations, dates, developmental stages and sample sizes for AFLP and mtDNA analyses of rainbow smelt.</p

Variance explained by historical lineage and genetic admixture when smelt populations are subdivided in four groups in a DFA: estuarine smelt populations of pure Acadian and Atlantic origin (Ac pure and At pure), estuarine smelt populations showing evidence of admixture with the alternate historical lineage (Ac mixed, At mixed).

<p>The random ANOVA models (with crossed and nested factors) partitioned variance, on the two main canonical axes (Axis 1 and Axis 2) of the DFA, among the following contrasts (1) Ac pure vs At pure, (2) Ac mixed vs Ac pure, (3) At mixed vs At pure, (4) the remaining among populations variability nested within groups “Pop_(group)”, and (5) the within population variability “Error”. Axis 1- the first discriminant function. Axis 2- the second discriminant function.</p><p>Variance explained by historical lineage and genetic admixture when smelt populations are subdivided in four groups in a DFA: estuarine smelt populations of pure Acadian and Atlantic origin (Ac pure and At pure), estuarine smelt populations showing evidence of admixture with the alternate historical lineage (Ac mixed, At mixed).</p