This study presents a Monte Carlo method (CMSY) for estimating fisheries reference points from catch, resilience and qualitative stock status information on data‐limited stocks. It also presents a ...Bayesian state‐space implementation of the Schaefer production model (BSM), fitted to catch and biomass or catch‐per‐unit‐of‐effort (CPUE) data. Special emphasis was given to derive informative priors for productivity, unexploited stock size, catchability and biomass from population dynamics theory. Both models gave good predictions of the maximum intrinsic rate of population increase r, unexploited stock size k and maximum sustainable yield MSY when validated against simulated data with known parameter values. CMSY provided, in addition, reasonable predictions of relative biomass and exploitation rate. Both models were evaluated against 128 real stocks, where estimates of biomass were available from full stock assessments. BSM estimates of r, k and MSY were used as benchmarks for the respective CMSY estimates and were not significantly different in 76% of the stocks. A similar test against 28 data‐limited stocks, where CPUE instead of biomass was available, showed that BSM and CMSY estimates of r, k and MSY were not significantly different in 89% of the stocks. Both CMSY and BSM combine the production model with a simple stock–recruitment model, accounting for reduced recruitment at severely depleted stock sizes.
•We present JABBA: a new open-source software for biomass dynamic stock assessment.•JABBA rapidly generates reproducible stock status estimates of interest for fisheries management.•Exclusive visual ...diagnostic tools to aid in identifying data conflicts.•Option to automatically produce future projections and retrospective analysis.
This study presents a new, open-source modelling software entitled ‘Just Another Bayesian Biomass Assessment’ (JABBA). JABBA can be used for biomass dynamic stock assessment applications, and has emerged from the development of a Bayesian State-Space Surplus Production Model framework, already applied in stock assessments of sharks, tuna, and billfishes around the world. JABBA presents a unifying, flexible framework for biomass dynamic modelling, runs quickly, and generates reproducible stock status estimates and diagnostic tools. Specific emphasis has been placed on flexibility for specifying alternative scenarios, achieving high stability and improved convergence rates. Default JABBA features include: 1) an integrated state-space tool for averaging and automatically fitting multiple catch per unit effort (CPUE) time series; 2) data-weighting through estimation of additional observation variance for individual or grouped CPUE; 3) selection of Fox, Schaefer, or Pella-Tomlinson production functions; 4) options to fix or estimate process and observation variance components; 5) model diagnostic tools; 6) future projections for alternative catch regimes; and 7) a suite of inbuilt graphics illustrating model fit diagnostics and stock status results. As a case study, JABBA is applied to the 2017 assessment input data for South Atlantic swordfish (Xiphias gladius). We envision that JABBA will become a widely used, open-source stock assessment tool, readily improved and modified by the global scientific community.
Based on the requirement of the international conventions, there is a pressing need for inventory of NH3, CH4, CO2 and N2O emissions from livestock buildings. The main aim of this study was to ...quantify the gas emissions and investigate the influence of the climatic factors on ammonia emissions. The measurements were carried out in two naturally ventilated dairy cattle buildings with different layouts, floor types and manure management systems during three periods covering winter and summer time. Air temperature and the three dimensional air velocities inside and outside the buildings were recorded over the course of summer period. Emission rates were determined by CO2 production model.
The results showed that the internal concentrations of NH3, CH4 and CO2 were increased or decreased simultaneously. Low concentration of N2O was measured outside and inside the buildings; the difference of the concentrations were also very low. The variation of CH4 and CO2 concentrations showed a strong correlation. The NH3 emission rates varied from 32 to 77 g HPU−1 d−1 in building 1 and varied from 18 to 30 g HPU−1 d−1 in building 2. The average emission of CH4 was 290 and 230 g HPU−1 d−1 from building 1 and 2, respectively. Diurnal pattern was found for NH3 and CH4 emission rates. From multiple linear regression models, there was a significant linear relationship between NH3 emission rates and climatic factors including the external wind speed as well as the air temperature (P < 0.001), but not with the external wind directions (P > 0.05).
► Variation of internal concentrations of NH3, CH4 and CO2 followed the same trend. ► NH3 emission rates varied from 18 to 77 g HPU−1 d−1 for the two buildings. ► Diurnal pattern was found for NH3 and CH4 emission rates. ► A linear relationship existed between NH3 emission and wind speed (P < 0.001). ► A linear relationship was found between NH3 emission and air temperature (P < 0.001).
Environmental change and anthropogenic activity, alone or in combination, may cause vital rates of fish populations to exhibit low‐frequency, large‐magnitude variation leading to non‐stationary ...population processes in inherently dynamic ecosystems. It remains unclear why, when and, so, whether, non‐stationary population processes should be taken into account in fisheries stock assessment models. Here, we clarify the necessity and conditions for including non‐stationary population processes in stock assessment models. Specifically, the convention of treating population vital rates with constant parameters might be unreliable under regime shifts characterized by low‐frequency, large‐magnitude variation in drivers of fish population dynamics. We hypothesized and simulated effects of a U‐shaped trade‐off between the length of time‐series data and model estimation error for fish populations exhibiting non‐stationary dynamics. In the case of low‐frequency, large‐magnitude variation, when measurement errors were small, the effects of non‐stationary population processes were stronger than otherwise. Including time‐varying parameters of population vital rates in the assessment model resolved this dilemma as anticipated, albeit at the cost of increased model complexity, suggesting that accounting for non‐stationarity with time‐varying parameters alone may not be sufficient to improve stock assessments and other approaches should also be considered.
Despite the importance of Agulhas Bank (AB) marine productivity in supporting South African coastal fisheries and shelf ecosystems, there are relatively few regional-scale assessments of its spatial ...and temporal variability, and most productivity studies have been limited in scale. Here we use satellite-derived Net Primary Production (NPP) rates calculated using the Vertically Generalized Production Model (VGPM) to examine the spatial and temporal dynamics of NPP over the 21-year satellite record (1998–2018) on the AB. In calculating VGPM NPP we used the OCCI Chlorophyll-a product, SST from Operational-Sea-Surface-Temperature-and-Sea-Ice-Analysis (OSTIA) and PAR from GlobColour level-3 mapped products as these represent the longest datasets that fit our extended study period. We examine spatial trends between the eastern and central AB, as well as three areas of the bank (around Port Alfred, the Tsitsikamma coast, and the ‘cold ridge’) that have been previously identified as contributing significantly to the overall productivity of the AB. The AB shows only a moderate degree of seasonality in NPP calculated from the VGPM, with NPP being highest in austral summer (1.7–1.8 g C m−2 d−1) and lowest in winter (0.9–1.0 g C m−2 d−1), and remains relatively high (>1 g C m−2 d−1) throughout the year, contrasting sharply with other shelf systems. Considered annually, NPP on the bank was 516 g C m−2 yr−1 (38 Mt C yr−1 when scaled to the total shelf area) which is higher than many other shelf systems though lower than the neighbouring Benguela system and is indicative of a moderately productive shelf system fuelled by perennial NPP. Comparing different sections of the AB from east to central bank, and including the three upwelling areas, highlighted that spatial differences in NPP were relatively limited; that these three upwelling areas made similar contributions to their relative proportion of the total shelf area, and that average rates of NPP are spatially similar across the bank, though notable high rates occur in some coastal upwelling areas. Interannual variability in NPP was relatively modest, varying between years by only ∼15% over the two decades assessed. Over the 21-year data set, there was a slight (∼0.26% yr−1) statistically-significant decline in calculated NPP over time for the AB as a whole, which, when examined on a pixel-by-pixel basis, indicated that most of the decline was on the central bank between 100 m and 200 m isobaths. In summer, an increase in NPP occurred on the EAB (26.5–28°E). In conclusion, the AB is a significant site of perennial moderate levels of NPP, varying little interannually and with only a slight decline in NPP over time. These factors lead to a stable environment in terms of ecosystem productivity so that the AB makes a significant contribution to the productivity of South African regional fisheries.
•Detailed ozone and its precursors characteristics were presented in Zhengzhou, China.•Meteorological impact such as high T, low RH, south and southeast winds, and Moderately high wind speeds lead to ...urban ozone episodes.•Alkenes and aromatics contributed the most to O3 formation•VOCs/NOx ratio and SPM were jointly used to evaluate O3-VOC-NOx sensitivity.•Early summer O3 formation in Zhengzhou presents “VOC-limited and transition control region alternately” characteristic.
In this study, we conducted an observation experiment from May 1 to June 30, 2018 in Zhengzhou, a major city in central China, where ground ozone (O3) pollution has become serious in recent years. The concentrations of O3 and its precursors, as well as H2O2 and meteorological data were obtained from the urban site (Yanchang, YC), suburban (Zhengzhou University, ZZU) and background sites (Ganglishuiku, GLSK). Result showed that the rates of O3 concentration exceeded Chinese National Air Quality Standard Grade II (93.3 ppbv) were 59.0%, 52.5%, and 55.7% at the above three sites with good consistency, respectively, indicating that O3 pollution is a regional problem in Zhengzhou. The daily peak O3 appeared at 15:00–16:00, which was opposite to VOCs, NOx, and CO and consistent with H2O2. The exhaustive statistical analysis of meteorological factors and chemical effects on O3 formation at YC was advanced. The high concentration of precursors, high temperature, low relative humidity, and moderately high wind speed together with the wind direction dominated by south and southeast wind contribute to urban O3 episodes in Zhengzhou. O3 formation analysis showed that reactive alkenes such as isoprene and cis-2-butene contributed most to O3 formation. The VOCs/NOx ratio and smog production model were used to determine O3-VOC-NOx sensitivity. The O3 formation in Zhengzhou during early summer was mainly under VOC-limited and transition regions alternately, which implies that the simultaneous emission reduction of alkenes and NOx is effective in reducing O3 pollution in Zhengzhou.
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In this paper, the Riemann solutions for the macroscopic production model with chaplygin gas under some special initial data are constructively obtained in the fully explicit form. An interesting ...composite wave RδJ is observed, it is formed by a rarefaction wave R and a left-contact delta discontinuity δJ attached to the wavefront of the rarefaction wave. Furthermore, this delta discontinuity gradually absorbs the rarefaction wave and eventually forms a delta shock wave under some suitable initial condition. In addition, we give some typical numerical results that coincide well with the theoretical analysis.
This paper presents the first estimates, at the global scale, of energy use by energy type associated with individual steps in the production of fabricated steel products. Estimates are averaged over ...the period 2016–20, based on a synthesis of literature regarding energy use for (i) preparation of iron ore; (ii) production of iron in a blast furnace (BF) and as direct reduced iron; (iii) production of refined steel in the basic oxygen furnace or electric arc furnace; (iv) steel casting, hot and cold rolling, and coating; (v) fabrication of intermediate steel products; and (vi) processing of scrap. The International Energy Agency provides separate global energy use for coking, transformation energy use by BF, and by the remainder of the iron and steel industry (rISI) including the remaining BF energy use. With re-allocation of the BF portion of rISI back to BF, and a 9% increase in literature-based estimates of energy intensity across all production steps except coking, bottom-up and IEA estimates of total energy use agree. The resulting mean cumulative energy intensity of fabricated steel products is 24.1 GJ/t. The energy content of the lost iron equals about 10% of the total energy used in producing finished steel products.
•Reconciles bottom-up and top-down estimates of global iron & steel energy use.•Breakdown of energy use by energy type and process.•Embodied energy of fabricated steel products and various iron losses is computed.
In our present work, we analyze the limiting behaviour of solution to the Riemann problem for a macroscopic production model with van der Waals equation of state. We construct the solution to the ...Riemann problem of the governing system which consists of only classical elementary waves and observe vacuum state for certain initial data. In the limiting process we establish the formation of extreme concentration for a state variable in terms of Dirac delta distribution. Further it is observed that the delta shock solution of the governing system is different from that of pressureless gas dynamics system so a perturbation to the flux is made and the intrinsic phenomena of concentration and cavitation is examined in the limiting case. Additionally we perform numerical simulations to note the effect of van der Waals parameter on the solution of the Riemann problem and to observe the formation of delta shock and vacuum state in the limiting cases.
•A macroscopic production model is investigated.•Limiting behaviour of the solution of the Riemann problem is successfully developed and validated.•The influence of delta shock wave is explored.•Successful verification of the results of the proposed solution in a special case.
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