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Beverton and Holt’s (1957. On the dynamics of exploited fish populations. UK Ministry of Agriculture, Fisheries and Food. Fisheries Investigations, 2: 533 pp.) monograph contributed a widely used stock–recruitment relationship (BH-SRR) to fisheries science. However, because of variation around a presumed relationship between spawning biomass and recruits, the BH-SRR is often considered inadequate and approached merely as a curve-fitting exercise. The commonly used and simplified version of the BH-SRR has eclipsed the fact that in their classic monograph, the derivation accounted for mechanistic recruitment processes, including multi-stage recruitment with explicit cohort-dependent and -independent mortality terms that represent competition between recruits and extrinsic, cohort-independent factors such as the environment or predation as two independent sources of mortality. The original BH-SRR allows one to recreate recruitment patterns that correspond to observed ones. Doing so shows that variation in density-independent mortality increases the probability of overlooking an underlying stock–recruitment relationship. Intermediate coefficients of variation in mortality (75–100%) are sufficient to mask stock–recruitment relationships and recreate recruitment time series most similar to empirical data. This underlines the importance of variation in survival for recruitment and that Beverton and Holt’s work still provides a fundamental and useful tool to model the dynamics of populations.

Intraspecific competition in large aggregations of animals should generate density-dependent effects on foraging patterns. To test how large differences in colony size affect foraging movements, we tracked seasonal movements of the African straw-coloured fruit bat ( Eidolon helvum ) from four colonies that range from 4000 up to 10 million animals. Contrary to initial predictions, we found that mean distance flown per night (9–99 km), number of nightly foraging sites (2–3) and foraging and commuting times were largely independent of colony size. Bats showed classic central-place foraging and typically returned to the same day roost each night. However, roost switching was evident among individuals in three of the four colonies especially towards the onset of migration. The relatively consistent foraging patterns across seasons and colonies indicate that these bats seek out roosts close to highly productive landscapes. Once foraging effort starts to increase due to local resource depletion they migrate to landscapes with seasonally increasing resources. This minimizes high intraspecific competition and may help to explain why long-distance migration, otherwise rare in bats, evolved in this highly gregarious species.

A systematic study of the central depletion of proton density has been performed in the isotonic chains of nuclei with neutron numbers $N = 20$ and $28$ using different variants of the relativistic mean-field (RMF) models. These models include either the non-linear contributions from the mesons with the coupling constants being density independent or the non-linearity of the mesonic fields realized through the density dependent coupling strengths. The central depletion in deformed nuclei tends to disappear irrespective of the occupancy of $2s_{1/2}$ state in contrast to the spherical nuclei in which the unoccupancy of $2s_{1/2}$ state leads to the central depletion. Due to the differences in the strength of spin-orbit potentials in these models, the central depletions are found to be model dependent. The influence of the central depletion on the neutron-skin thickness is also investigated. It appears that the effects of the central depletion do not percolate far enough to display its finger prints on the trends of the neutron-skin thickness., 17 pages, 9 figures, Accepted in Journal of Physics G: Nuclear and Particle Physics

People counting in high density crowds is emerging as a new frontier in crowd video surveillance. Crowd counting in high density crowds encounters many challenges, such as severe occlusions, few pixels per head, and large variations in person's head sizes. In this paper, we propose a novel Density Independent and Scale Aware model (DISAM), which works as a head detector and takes into account the scale variations of heads in images. Our model is based on the intuition that head is the only visible part in high density crowds. In order to deal with different scales, unlike off-the-shelf Convolutional Neural Network (CNN) based object detectors which use general object proposals as inputs to CNN, we generate scale aware head proposals based on scale map. Scale aware proposals are then fed to the CNN and it renders a response matrix consisting of probabilities of heads. We then explore non-maximal suppression to get the accurate head positions. We conduct comprehensive experiments on two benchmark datasets and compare the performance with other state-of-theart methods. Our experiments show that the proposed DISAM outperforms the compared methods in both frame-level and pixel-level comparisons. © 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

At present, the giant impact (GI) is the most widely accepted model for the origin of the Moon. Most of the numerical simulations of GI have been carried out with the smoothed particle hydrodynamics (SPH) method. Recently, however, it has been pointed out that standard formulation of SPH (SSPH) has difficulties in the treatment of a contact discontinuity such as a core-mantle boundary and a free surface such as a planetary surface. This difficulty comes from the assumption of differentiability of density in SSPH. We have developed an alternative formulation of SPH, density independent SPH (DISPH), which is based on differentiability of pressure instead of density to solve the problem of a contact discontinuity. In this paper, we report the results of the GI simulations with DISPH and compare them with those obtained with SSPH. We found that the disk properties, such as mass and angular momentum produced by DISPH is different from that of SSPH. In general, the disks formed by DISPH are more compact: while formation of a smaller mass moon for low-oblique impacts is expected with DISPH, inhibition of ejection would promote formation of a larger mass moon for high-oblique impacts. Since only the improvement of core-mantle boundary significantly affects the properties of circumplanetary disks generated by GI and DISPH has not been significantly improved from SSPH for a free surface, we should be very careful when some conclusions are drawn from the numerical simulations for GI. And it is necessary to develop the numerical hydrodynamical scheme for GI that can properly treat the free surface as well as the contact discontinuity., Comment: Accepted for publication in Icarus

Habitat use of aquatic organisms is essential to evaluate effects of many environmental challenges like effects of hydro-power regulation, where stranding may occur under hydropeaking (rapid dewatering of shallow river areas). Experimental studies as well as observations from nature with juvenile Atlantic salmon (Salmo salar) show that the proportion of the population that uses shallow depth was both independent of population density and decreasing with fish size. Experiments were conducted both in the presence and in absence of older fish, during day and night, and during all four seasons. Juvenile salmon from deep areas may therefore distribute into the shallow areas even when fish density becomes reduced. Thus, low density does not lead to reduced stranding risk and shallow areas may therefore function as a sink in a within-generation source-sink dynamic under a repeated hydropeaking scenario. The sink effect of rapid dewatering in shallow areas may be mitigated by e.g. seasonal and diurnal regulation of hydropeaking activity, but dewatering may still result in extinction of weak populations. habitat use, hydropeaking, intracohort competition, intercohort competition, microhabitat use, stranding Copyright the Author. Published by NRC Research Press (Canadian Science Publishing). This Just-IN manuscript is the accepted manuscript prior to copy editing and page composition. It may differ from the final official version of record.

We propose density independent hydrodynamics model (DIHM) which is a novel and automatic method for coherency detection in crowded scenes. One of the major advantages of the DIHM is its capability to handle changing density over time. Moreover, the DIHM avoids oversegmentation and thus achieves refined coherency detection. In the proposed DIHM, we first extract a motion flow field from the input video through particle initialization and dense optical flow. The particles of interest are then collected to retain only the most motile and informative particles. To represent each particle, we accumulate the contribution of each particle in a weighted form, based on a kernel function. Next, the smoothed particle hydrodynamics (SPH) is adopted to detect coherent regions. Finally, the detected coherent regions are refined to remove the effects of oversegmentation. We perform extensive experiments on three benchmark datasets and compare the results with 10 state-of-the-art coherency detection methods. Our results show that DIHM achieves superior coherency detection and outperforms the compared methods in both pixel level and coherent region level average particle error rates (PERs), average coherent number error (CNE) and F-score. © 2018. This is the authors’ accepted and refereed manuscript to the article. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

The density-independent mortality, considered in the stock-recruitment model of Ricker, was related to the interannual variability of the sea surface temperature (SST) during 1981 to 1993 in Bahía Magdalena, Baja California Sur and Isla Cedros, Baja California, Mexico. From the stock-recruitment curve fitted to the observed data the variation in the density-independent mortality was estimated, maintaining fixed the value of the density-dependent coefficient. The density-independent parameters estimated in this way were related to the SST by using a functional relationship that considers six principal components. This function permitted identification of the changes of the density-independent mortality and its relation to the recruitment of the Pacific sardine Sardinops caeruleus. We determined density-independent mortality greater than 3.38 as years with recruitment greater than 25,000 t, and density-independent mortality less than 3.38 as years with recruitment less than 15,000 t. The seasons of greatest influence on the density-independent mortality in relation to the SST were autumn, winter and spring in both regions (Bahía Magdalena and Isla Cedros). In these seasons when the SST > 19.3°C (warmer waters) the variations in recruitment of Pacific sardine were observed. La mortalidad denso independiente considerada en el modelo de stock reclutamiento de Ricker fue relacionada con la variabilidad interanual de la temperatura superficial del mar (TSM), durante el periodo de 1981 a 1993 en Bahía Magdalena, Baja California Sur e Isla Cedros, Baja California, México. Ajustando la curva stock reclutamiento a los datos observados, se estimó la variación de la mortalidad denso independiente, manteniendo constante el valor del coeficiente de mortalidad denso dependiente. Los parámetros de denso independencia estimados de ésta forma, fueron relacionados con la TSM usando una relación funcional que considera seis componentes principales. Esta función permitió identificar los cambios en la mortalidad denso independiente y su relación con el reclutamiento de la sardina del pacífico Sardinops caeruleus. Se determinó una mortalidad denso independiente > 3.38 como años con reclutamiento > 25,000 t, y mortalidad denso independiente < 3.38 como años con reclutamiento < 15,000 t. Las estaciones de mayor influencia sobre la mortalidad denso independiente en relación a la TSM fueron: otoño, invierno y primavera en ambas regiones (Bahía Magdalena e Isla Cedros). En estas estaciones fueron observadas las variaciones en reclutamiento de la sardina del pacífico cuando la TSM > 19.3°C (aguas cálidas).

© 2015 The Author(s) Published by the Royal Society. Climatic variation has been invoked as an explanation of population dynamics for a variety of taxa. Much work investigating the link between climatic forcings and population fluctuation uses single-taxon case studies. Here, we conduct comparative analyses of a multi-decadal dataset describing population dynamics of 50 co-occurring butterfly species at 10 sites in Northern California. Specifically, we explore the potential commonality of response to weather among species that encompass a gradient of population dynamics via a hierarchical Bayesian modelling framework. Results of this analysis demonstrate that certain weather conditions impact volatile, or irruptive, species differently as compared with relatively stable species. Notably, precipitation-related variables, including indices of the El Niño Southern Oscillation, have a more pronounced impact on the most volatile species. We hypothesize that these variables influence vegetation resource availability, and thus indirectly influence population dynamics of volatile taxa. As one of the first studies to showa common influence ofweatheramong taxa with similar population dynamics, the results presented here suggest newlines of research in the field of biotic-abiotic interactions.

The smoothed particle hydrodynamics (SPH) method is a useful numerical tool for the study of a variety of astrophysical and planetlogical problems. However, it turned out that the standard SPH algorithm has problems in dealing with hydrodynamical instabilities. This problem is due to the assumption that the local density distribution is differentiable. In order to solve this problem, a new SPH formulation, which does not require the differentiability of the density, have been proposed. This new SPH method improved the treatment of hydrodynamical instabilities. This method, however, is applicable only to the equation of state (EOS) of the ideal gas. In this paper, we describe how to extend the new SPH method to non-ideal EOS. We present the results of various standard numerical tests for non-ideal EOS. Our new method works well for non-ideal EOS. We conclude that our new SPH can handle hydrodynamical instabilities for an arbitrary EOS and that it is an attractive alternative to the standard SPH., 15 pages, 8 figures

Continuous input models of the ideal free distribution usually assume that resources are consumed immediately that they enter a patch. This paper presents models of constant continuous input in which this assumption is relaxed, so that predictions can be made about the standing crops of resources and the density relationship of prey mortality caused by the consumers. These models suggest that: (1) the input matching rule is not dependent on the assumption that resources are consumed immediately that they enter a patch, and holds whether or not there is interference competition but not when there is an alternative source of mortality; (2) exploitation competition is fundamental to the continuous input model. Whether or not interference competition occurs can be determined in experimental situations by measuring the standing crops of resources in patches with different resource input rates; (3) interference models are not an alternative to continuous input models but represent a 'snapshot' of time from either continuous input or depletion models; (4) in continuous input models prey mortality is density independent in the absence of interference because all patches have the same standing crop of resources. When there is interference between consumers prey mortality is density dependent, unless the interference is extremely strong. [KEYWORDS: INDIVIDUAL DECISIONS; PATCHY ENVIRONMENT; PREDATORS; STRATEGY]

GAYGUSUZ, Ozcan/0000-0001-6861-6221; Gaygusuz, Ozcan/0000-0001-6861-6221; Tarkan, Ali Serhan/0000-0001-8628-0514 WOS: 000244325600002 A population of the invasive Prussian carp (Carassius gibelio) was examined over a three-year period in a mesotrophic reservoir to find out interannual variations of fecundity and egg size and the influence of maternal condition (total length, TL, and age class) and environmental factors (water temperature and fish density) on these variables. Prussian carp reproduction was synchronous, with only a single batch, and fecundity ranged from 1,250 to 62,400 eggs per female. Relative fecundities and egg size showed no significant between-year differences. Fecundity increased with age, whereas egg diameter remained unchanged with age and TL. Fecundity was affected positively by TL and negatively by fish density, whereas temperature had no significant effect. Egg size was not affected by fish density or temperature.

We tracked the movement of people during a one year span in a shopping mall to study pedestrian behaviour under different density and usage conditions. We analyse the time and space dependence of pedestrian density and velocity, showing good agreement with the predictions of our “social norm” collision model. We also show that along with the expected decrease of velocity with growing density, we find density independent time patterns, corresponding to higher velocity in working days and during “rush hours”, and also a general tendency to have slower velocities in later hours. We also report a positive correlation of pedestrian velocity with human height, an effect weaker on weekends

In this paper, we study two species time-delayed predator–prey Lotka–Volterra type dispersal systems with periodic coefficients, in which the prey species can disperse among n patches, while the density-independent predator species is confined to one of patches and cannot disperse. Sufficient conditions on the boundedness, permanence and existence of positive periodic solution for this systems are established. The theoretical results are confirmed by a special example and numerical simulations.

Using 5 density levels, the effect of increasing density was studied on several population statistics of adultDelia (=Hylemya) antiqua. Amongst the statistics studied were adult lifespan; female mating frequency, fecundity and egg hatchability. It was shown that females lived significantly longer than males and that increasing density significantly reduced lifespan. Density had no effect on mating frequency. Total fecundity/female was significantly reduced with increasing density but oviposition rate was density independent.