Sustainable harvest of fish stocks requires regular monitoring of abundance and biomass in space and time. In Southeast Greenland, two Sebastes species, beaked redfish (Sebastes mentella) and golden redfish (S. norvegicus), coexist and have been harvested together. However, the species differ greatly in stock status as beaked redfish are depleted, while golden redfish have a surplus of exploitable biomass. Detailed habitat affinities of both species along the continental shelf and slope are largely unknown despite documented differences in depth distribution. Yet, such information is crucial for effective management and conservation given policies greatly constraining beaked redfish catches. Furthermore, investigating the distribution of these predator species is important to understand the changing sub-Arctic ecosystem of Southeast Greenland. Here we combine three fisheries survey time series to compare and predict distribution patterns of population density and identify their drivers. Spatiotemporal generalized linear mixed models were implemented in the sdmTMB framework. The most appropriate models were identified based on 5-fold cross-validation and ecological realism of partial effects. Our models confirmed that 1) spatial aggregations are common for both species, however, beaked redfish showed a broader spatial autocorrelation compared to golden redfish, shown in greater Matérn spatial range (43 km vs 20 km), 2) both species are widely distributed over the shelf and slope but with local/regional hotspots that remain relatively constant over time despite interannual changes in biomass. Golden redfish displayed larger spatiotemporal variability in distribution compared with beaked redfish, and 3) beaked redfish occupy deeper areas compared to golden redfish indicating vertical segregation. Depth and density of Atlantic cod (Gadus morhua), which is another important predator in the area, were the most important drivers for beaked redfish distribution, while depth and temperature were most important for golden redfish. These findings highlight the importance of distribution models to understand co-occurrence patterns of closely related species and provide opportunities to improve fisheries management.
Calhoun’s Universe 25 experiment remains a significant and contested case study of population growth, crowding, social disruption and reproductive decline in a protected mouse population. Although commonly interpreted as evidence of physical overpopulation, its central implication may instead lie in the distinction between physical and social carrying capacity. This paper develops a System Dynamics reinterpretation of Universe 25 to formalise the feedback mechanisms linking population growth, social-role saturation, behavioural disruption, maternal failure, reduced births, ageing and population decline. The model represents the population through age- and behaviour-structured stocks, including pups, immature mice, competent adults, displaced adults, withdrawn adults and senescent adults, together with a stock of social integrity. Flows describe births, weaning, maturation, displacement, withdrawal, ageing, mortality and the deterioration of social organisation. The model is presented as a formal dynamic hypothesis that enables exploratory sensitivity analysis of mechanisms implicit in the original experiment, including social niche capacity, contact pressure, maternal-care degradation, reproductive suppression, reduced mortality and the absence of dispersal. By separating resource adequacy from social organisation, the model offers a framework for assessing which mechanisms are sufficient to reproduce the observed transition from rapid growth to stagnation, reproductive decline and extinction. The analysis also clarifies the limits of direct extrapolation from Universe 25 while identifying its potential relevance for managed animal populations, including livestock systems, captive breeding, conservation enclosures and wildlife populations. The paper argues that Universe 25 can be interpreted as a possible case of endogenous social regulation failure under abundant resources, restricted dispersal and cumulative behavioural disruption.
Among human-induced environmental changes, increasing water temperature is one of the most well-documented consequences of climate change, and is likely to influence the nursery function of estuarine environments. However, our ability to assess these effects remains limited at the individual level, and mechanistic models applicable at the population level are still lacking.To investigate the specific effects of temperature on the individual life-history traits of juvenile common soles (Solea solea) in the Gironde estuary we employed a bioenergetic model based on Dynamic Energy Budget (DEB) theory. Assuming that the estuary has reached its maximum trophic carrying capacity, these effects were also evaluated under two conditions of limited energy availability (applied either globally on the available food, increasing competition, or equally on all juvenile), using temperature projections based on IPCC scenarios.At the individual scale, when energy limitation is caused by unlimited individual feeding, our model predicts that sole will grow more rapidly and reach sexual maturity earlier with increasing temperature, as they remain below their thermal optimum. This scenario implies increased individual energetic demand which can be sustained only with a reduced number of juveniles in the estuary in a context of limited food. Conversely, when energy limitation is equally distributed across all juveniles of the estuary, no significant changes in growth or maturation (i.e., age and length at maturity) are predicted with increasing temperatures; however, our model also predicts a reduction in energy reserves, potentially altering responses to other environmental changes.
Fungicide residues in table grapes are a critical food-safety concern because the fruit is consumed fresh, often with the skin, and grapes rank among the commodities with the highest frequency of Maximum Residue Limit (MRL) exceedances in European Union and Brazilian monitoring programmes. We present a Level IV fugacity model for the three-compartment grape berry (boundary air layer, lipidic skin, aqueous pulp) that extends the periodic fugacity control-system framework to incorporate (i) ionisation correction via the Henderson–Hasselbalch equation, (ii) compound-specific cuticular permeability following the Riederer–Schreiber model, (iii) logistic berry growth, and (iv) Arrhenius-dependent degradation rates derived from experimental DT50 values. The model is applied to 11 fungicides used in Brazilian viticulture. Reference degradation rates are derived from experimental DT50 values per compound and compartment, correcting a systematic underestimation by a factor of 15 to 154. The model reproduces the field observation that degradation accounts for 52%–100% of the initial mass within 240 h when calibrated with experimental DT50 values. The Spearman correlation between DT50,pulp and residual skin fraction at 240 h is ρ=0.96 (p<0.001): persistence governs long-term skin residue more strongly than lipophilicity or cuticular permeability. Cymoxanil (fn⋅Kow=0.15<1) is the only compound with a thermodynamic driving force towards the pulp; rapid degradation prevents this from producing measurable pulp penetration. A Monte Carlo analysis (N=500 per compound) with Partial Rank Correlation Coefficient sensitivity assessment reveals that mean temperature and DT50 are the dominant parameters (|PRCC|=0.88–0.95), temperature acting simultaneously on degradation, volatilisation, and air diffusivity. A 10°C regional temperature range shifts the predicted skin fraction of persistent compounds by 29–33 percentage points, providing a quantitative basis for region-specific pre-harvest interval recommendations.
In this paper, we present an analytical framework to examine the transmission dynamics of malaria outbreaks. The proposed modelling framework successfully captures the malaria outbreak in the Indian state of Madhya Pradesh. The sensitivity analysis discover that the malaria transmission dynamics is sensitive to seasonal and behavioral parameters, such as relative transmission factor, baseline mean temperature, phase shift of the temperature wave, and baseline human behavioral intervention. The number of infections amplifies as the relative transmission factor enhances. Initially, with an augmentation in the baseline mean temperature, the infections increase to attain a maxima. Then, any further increase in the baseline mean temperature causes the number of infections to decline. In addition, we discover that the coincidence of the peak of the temperature wave with monsoon months causes an augmentation in the number of infections. Besides, we found that an augmentation in baseline human intervention significantly reduces the number of infections.
