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Natural mortality rates (M) are poorly quantified and commonly identified as a key source of uncertainty in fish stock assessments. Increasingly, stock assessments account for size- and age-dependence in M instead of using a constant M for all sizes and ages, as has traditionally been the default assumption. Empirical studies show that M is approximately inversely proportional to body length in fish populations, and this generalization has been used together with a von Bertalanffy growth curve to derive an age-dependent M. Here we extend this approach to the three commonly used growth functions of the Richards family (i.e., Logistic, von Bertalanffy, and Gompertz growth models). These models allow flexible production of various growth curves with a sigmoid shape and an upper asymptote, making them useful for displaying diverse growth curves for various long-lived fishes. The influences of growth parameters on predicted M were investigated, and the outcomes were compared among the three growth models. Age-dependent M for blue sharks (Prionace glauca) were estimated as an example. [ABSTRACT FROM AUTHOR]

• Lattice-gas model is applied to prey-predator metapopulation system. • We consider the limiting space of patches, and introduce swapping migration. • To know population dynamics, a reaction-migration equation is presented. • Dynamics and extinction points are largely affected by the patch capacities. Many species live in spatially separated patches, and individuals can migrate between patches through paths. In real ecosystems, the capacities of patches are finite. If a patch is already occupied by the individuals of some species, then the migration into the patch is impossible. In the present paper, we deal with prey-predator system composed of two patches. Each patch contains a limited number of cells, where the cell is either empty or occupied by an individual of prey or predator. We introduce "swapping migration" defined by the exchange between occupied and empty cells. An individual can migrate, only when there are empty cells in the destination patch. Reaction-migration equations in prey-predator system are presented, where the migration term forms nonlinear function of densities. We numerically solve equilibrium densities, and find that the population dynamics are largely affected by nonlinear migration. Not only extinction points but also the responses to the environmental changes crucially depend on the patch capacities. [ABSTRACT FROM AUTHOR]

In the present study, we characterized the Fe–Al intermetallic phases formed in interstitial-free (IF) steel hot-dipped in a Zn–6Al–3Mg (wt.%) alloy melt at different temperatures (400, 460 and 500 °C) and dipping times (from 2 to 3600 s). Chemical composition analyses indicated Fe dissolution into the Zn alloy melt even after 2 s of dipping. Microstructural characterization revealed the initial formation of a continuous θ-Fe 4 Al 13 phase layer, followed by the local growth of η-Fe 2 Al 5 phase toward both steel and Zn alloy melt sides during the hot-dipping process. After long-term hot-dipping, further growth of the η phase was accompanied by significant dissolution of Fe into the Zn alloy melt, resulting in the loss of thickness of the IF steel sheets. Altogether, we rationalized the formation mechanism of Fe–Al intermetallic phases and their associated growth at the interface between solid Fe and liquid Zn alloy in terms of a Zn–Al–Mg–Fe quaternary phase diagram, calculated according to thermodynamic database available in the literature. • Fe–Al intermetallic phases formed in hot-dip Zn–6Al–3Mg alloy coating on steel sheets was characterized. • A continuous θ-Fe 4 Al 13 phase layer was initially formed, followed by the local growth of η-Fe 2 Al 5 phase. • The growth of the η phase was accompanied by significant dissolution of Fe into the Zn alloy melt. • The formation sequence of Fe–Al intermetallics was rationalized according to the calculated Zn–Al–Mg–Fe phase diagram. [ABSTRACT FROM AUTHOR]

We have developed a population dynamics model that considers the spatial segregation by sex and ontogenetic stages of pelagic sharks. The model was used to evaluate the performance of harvest strategies based on ecological characteristics. We proposed five harvest strategies for longline fisheries based on the ecological characteristics of blue shark ( Prionace glauca) in the North Pacific. Management objectives for depleted populations are to increase yield to the level that provides maximum sustainable yield through increases in biomass without collapsing the fishery. Deterministic and stochastic analyses were undertaken. We determined that the harvest of male sharks was robust to uncertainty of environmental changes, reducing the likelihood of fishery collapse and stabilizing yield and mean biomass. The harvest of male sharks was also robust to the uncertainties of biological parameters such as natural mortality and steepness. These results suggested that if there was no sperm limitation or impact on the mating behavior of the species, the harvest of males would be the most appropriate harvest strategy for blue shark in the North Pacific. [ABSTRACT FROM AUTHOR]

Iterated prisoner’s dilemma game is carried out on lattice with “colony” structure. Each cell is regarded as a colony which contains plural players with an identical strategy. Both intra- and inter-cellular interactions are assumed. In the former a player plays with all other players in the same colony, while in the latter he plays with one player each from adjacent colonies. Spatial patterns among four typical strategies exhibit various dynamics and winners. Both theory and simulation reveal that All Cooperation (AC) wins, when the members of colony or the intensity of noise increases. This result explains the evolution of altruism in animal societies, even though errors easily occur in animal communications. [ABSTRACT FROM AUTHOR]

A diazo-bridgedBODIPY dimer and tetramer were prepared by theoxidative coupling reaction of β-amino-substituted BODIPYs.The structure of the dimer was elucidated by X-ray diffraction analysis,showing its coplanar orientation of two BODIPY units. Effective extensionof π-conjugation was confirmed by optical and electrochemicalinvestigations. [ABSTRACT FROM AUTHOR]

Gause's law of competitive exclusion holds that the coexistence of competing species is extremely unlikely when niches are not differentiated. This law is supported by many mathematical studies, yet the coexistence of competing species is nearly ubiquitous in real ecosystems. We pay attention to the fact that plants and animals usually contact with microbial species as mutualistic partners. The activity spaces of host species are different from those of micro-organisms. In the present study, we apply double-layer model to the association of two competing hosts and a microorganism. Two lattices are prepared: one is for hosts, and the other is for microorganism. The basic equation obtained by mean-field theory is an extension of Lotka-Volterra competition model. Both mathematical analysis and numerical simulations reveal that a shared microbial mutualist can permit the coexistence of competing hosts. From the derived condition of coexistence, we believe the microbial mutualism promotes biodiversity in many ecological systems. [ABSTRACT FROM AUTHOR]

Estimating a shape parameter in a Bayesian state-space biomass dynamics model is an essential task in fisheries stock assessments because it is strongly associated with the status of the stock. However, it is frequently difficult to estimate the shape parameter accurately. If it is possible to statistically select the best model, which is closer to the true model, using information criteria, it will enable us to determine the shape parameter with high accuracy. To accomplish this goal, we evaluated the performance of five information criteria: widely applicable information criteria with conditional and marginal likelihoods (WAICc, WAICm), deviance information criteria with conditional and marginal likelihoods (DICc, DICm), and a widely applicable Bayesian information criterion (WBIC) using a numerical simulation for various scenarios. We also demonstrated an application of the methods to real-world fisheries stock assessment. We found five main results: (1) the performances of WAICm, DICm and WBIC were better than the conditional information criteria, (2) the relative performance of WAICm was unaffected by the magnitude of both observation and process errors, (3) the relative performance of WBIC and DICm was unaffected by the magnitude of process error, (4) WBIC was the most promising information criterion for selecting the shape parameter in the case study, and (5) the best model enhanced accuracy of the stock assessment. [ABSTRACT FROM AUTHOR]