Effects of recruitment variability and fishing history on estimation of stock-recruitment relationships: Two case studies from U.S. West Coast fisheries

2019 ◽  
Vol 217 ◽  
pp. 21-34 ◽  
Author(s):  
Xi He ◽  
John C. Field
Keyword(s):  
Case Studies ◽  
West Coast ◽  
Stock Recruitment ◽  
Recruitment Variability

scholarly journals Testing different methods of incorporating climate data into the assessment of US West Coast sablefish

2009 ◽  
Vol 66 (7) ◽  
pp. 1605-1613 ◽  
Author(s):  
Michael J. Schirripa ◽  
C. Phillip Goodyear ◽  
Richard M. Methot
Keyword(s):  
West Coast ◽  
Environmental Variability ◽  
Stock Assessment ◽  
Environmental Variable ◽  
Environmental Data ◽  
Observation Error ◽  
Climate Data ◽  
Simulation Techniques ◽  
Stock Recruitment ◽  
Us West

Abstract Schirripa, M. J., Goodyear, C. P., and Methot, R. M. 2009. Testing different methods of incorporating climate data into the assessment of US West Coast sablefish. – ICES Journal of Marine Science, 66: 1605–1613. The objective of this investigation was to evaluate different methods of including environmental variability directly into stock assessments and to demonstrate how this inclusion affects the estimation of recruitment parameters, stock status, and the conservation benchmarks used to manage a stock. Variations on two methods of incorporating environmental effects were tested. The first method (“model” method) utilizes a structural change in the stock–recruitment function to adjust the annual expected number of recruits by a value, either positive or negative, equal to that year's anomaly in the environmental variable. The second method (“data” method) allows for observation error in the environmental data and uses the time-series as an index to tune the vector of estimates of annual recruitment deviations. Simulation techniques were utilized to produce datasets of known quantities that were subsequently analysed with a widely used stock assessment platform. Under the circumstances simulated in this study, neither method could be said to have performed significantly better than the other in all situations. Because the two approaches handle years of missing data differently, the best approach is dictated by the available data, rather than a more appropriate method.

scholarly journals Evolution of A Type; A Case Study of Station Buildings in West Coastline, Malaysia During the British Era (1885-1957)

2021 ◽  
Author(s):  
Nor Hafizah Anuar ◽  
◽  
Musfika Gul Akdeniz ◽  
Nazende Yilmaz ◽  
◽  
...  
Keyword(s):  
Case Studies ◽  
West Coast ◽  
East Coast ◽  
Type A ◽  
Railway Station ◽  
The World ◽  
The City ◽  
Urban Places

The British intervention in Malaya resulted in the development of the railways as urgency of the expanding tin and rubber industries. This paper attempted to emphasize on the evolution of the station buildings’ plan types and its train-sheds. Railways were the pioneers of modern transportation introduced by the British in 1885 in Malaya. Although the terrain was the main difficulties in railway developments, they managed to connect the lines through West Coast and East Coast lines until Singapore on the southern part and Bangkok on the northern part in the year 1931. Case studies have been conducted and the analysis on plan type evolution will be made between the station buildings in Malaysia in parallel with station buildings around the world during that time. Together with the growth of the railway, the city blooms where it allows road constructions and buildings with different functions such as administrative buildings, railway station buildings and others started to fill major urban places.

scholarly journals Low to very high temperature thermal energy recycling – 3 case studies

2021 ◽  
Vol 313 ◽  
pp. 09001
Author(s):  
Arne Høeg ◽  
Tor-Martin Tveit
Keyword(s):  
High Temperature ◽  
Heat Source ◽  
Case Studies ◽  
Heat Pump ◽  
Thermal Energy ◽  
West Coast ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
The West ◽  
Very High

In this paper we present three case studies of the installation of a stirling-cycle high temperature heat pump applied to recycling thermal energy including steam generation. Many industries have heat demand at temperatures above 100°C and often the preferred energy carrier is steam. The optimal integration of a heat pump can be determined by investigating the thermal need of the process with pinch technology. For many industries, the pinch temperature is too high for conventional heat pumps. We present a heat pump solution that can recycle thermal energy and deliver this to a heat source up to 200°C, as hot water or steam. The heat pump can be integrated in a thermodynamic efficient way placing the sink and source in-between the pinch temperature. The working medium is a gas throughout the process cycle, with no evaporation or condensation. Thus, the process can auto-adjust to temperature variations and achieve very high efficiencies compared to the Carnot heat pump cycle. The coefficient of performance (COP) of the heat pump vary with the sink/source temperatures as the temperature fraction varies. Another important feature is that the medium has both a global warming potential (GWP) and ozone depletion potential (ODP) of zero. The thermodynamics of the heat pump is explained in more detail in the introduction section. The first installation is at a dairy plant on the west coast of Norway. In this installation, the heat pump provides cooling at 0-5°C and converts this heat into hot water at 120°C. The second installation is also at a dairy in Norway. Here the heat pump cools the ammonia from the cooling compressors at about 25-30°C and converts the heat to hot water at 110C°. The third installation is at a beverage plant on the west coast of Norway. Here the heat pump is providing cooling to compressors and other equipment. The final temperature of the heat source varies from 20-70°C. The heat is converted into steam at 168°C. In the case study sections, the installations are discussed in more details, together with the performance and a discussion of the experiences with the technology.

A Long Term Perspective of Landscape Evolution in a Coastal Interface: Case Studies from the Portuguese West Coast, Near the Aveiro Lagoon

2016 ◽  
pp. 129-144
Author(s):  
Maria Rosário Bastos ◽  
Olegário Pereira ◽  
Sérgio Monteiro-Rodrigues ◽  
João Pedro Tereso ◽  
João Pedro Cunha-Ribeiro
Keyword(s):  
Case Studies ◽  
West Coast ◽  
Landscape Evolution ◽  
Aveiro Lagoon

Effects of Density-Dependent and Climatic Factors on American shad, Alosa sapidissima, Recruitment: A Predictive Approach

1986 ◽  
Vol 43 (2) ◽  
pp. 457-463 ◽  
Author(s):  
Victor Crecco ◽  
Thomas Savoy ◽  
Walter Whitworth
Keyword(s):  
River Flow ◽  
Climatic Factors ◽  
American Shad ◽  
Connecticut River ◽  
Alosa Sapidissima ◽  
Density Dependent ◽  
Class Strength ◽  
Stock Recruitment ◽  
Parent Stock ◽  
Recruitment Variability

We developed environment-dependent stock–recruitment models for American shad, Alosa sapidissima, in the Connecticut River to forecast recruitment variability and measure density-dependent effects. These models were fitted to the 1966–78 stock–recruitment estimates and to May and June river flow, water temperature, and rainfall data shown previously to affect American shad year-class strength. We also attempted to validate the models by forecasting the 1979–84 year-classes based on juvenile indices, parent stock size, and hydrographic data for these years. The stock–recruitment models without environmental factors explained less than 3% of the recruitment variability, and none of the density-dependent exponents were statistically different from 0. The predictive capability of the Ricker stock–recruitment model improved dramatically (r2 = 0.90) when combined with mean May flows, June flows, and the number of American shad lifted over the Holyoke Dam. The density-dependent exponents of these multiple regression models were highly significant, indicating that density-dependent processes are hidden by climatically induced variability in recruitment. Two environment-dependent stock–recruitment models predicted 80–90% of the American shad recruitment variability from 1979–84.

Accounting for non-stationary stock–recruitment relationships in the development of MSY-based reference points

2020 ◽  
Author(s):  
Fan Zhang ◽  
Paul M Regular ◽  
Laura Wheeland ◽  
Rick M Rideout ◽  
M Joanne Morgan
Keyword(s):  
Case Studies ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Anthropogenic Impacts ◽  
Low Frequency ◽  
Maximum Sustainable Yield ◽  
Reference Points ◽  
Stock Recruitment ◽  
Traditional Approaches ◽  
Asymmetric Relationships

Asbtract Stock–recruitment relationships (SRRs) may vary over time due to ecological and anthropogenic impacts, challenging traditional approaches of calculating maximum sustainable yield (MSY)-based reference points that assume constant population traits. We compare seven methods to calculate MSY, FMSY and BMSY by modelling constant, stochastic (uncorrelated), and autocorrelated SRRs using simulations and two case studies [Atlantic cod (Gadus morhua) and American plaice (Hippoglossoides platessoides) on the Grand Bank off Newfoundland, Canada]. Results indicated that the method used to model SRRs strongly affected the temporal pattern of recruitment projection, and the variations generated by autocorrelated SRRs were more similar to observed patterns. When the population productivity had low-frequency and large-magnitude variations, stochastic SRRs generated greater MSY and FMSY estimates than constant or autocorrelated SRRs, while no consistent pattern of BMSY was detected. In the case studies, stochastic and autocorrelated SRRs produced asymmetric relationships between fishing mortality and yield, with higher risk of overfishing by going beyond FMSY. Overall, our results suggest that caution should be taken when calculating MSY-based reference points in highly dynamic ecosystems, and correctly accounting for non-stationary population dynamics could, therefore, lead to more sustainable fisheries.

How variable is recruitment for exploited marine fishes? A hierarchical model for testing life history theory

2014 ◽  
Vol 71 (7) ◽  
pp. 973-983 ◽  
Author(s):  
James T. Thorson ◽  
Olaf P. Jensen ◽  
Elise F. Zipkin
Keyword(s):  
Life History ◽  
Hierarchical Model ◽  
Life History Theory ◽  
Simulation Models ◽  
Fish Populations ◽  
Theoretical Research ◽  
Life History Variation ◽  
Stock Recruitment ◽  
Recruitment Variability ◽  
Bayesian Prior

Recruitment often varies substantially in fish populations, and residual variability may have serial autocorrelation due to environmental effects even after accounting for a stock–recruitment relationship. However, the likely magnitude of variability and autocorrelation in recruitment has yet to be formally estimated. We therefore developed a hierarchical model for recruitment variability and autocorrelation and applied it to data for 154 fish populations. Results were similar when using either the Ricker or Beverton–Holt stock–recruitment model, and showed that autocorrelated recruitment has a marginal standard deviation of 0.74 (SD = 0.35) and a mean autocorrelation of 0.43 (SD = 0.28) when predicting for an unobserved taxonomic order. Estimates differed somewhat among taxonomic orders and stocks, and also supported a hypothesized positive relationship between age at maturity and autocorrelation in recruitment. Our results can be used as a Bayesian prior for recruitment variability in models for data-poor stocks and to distinguish recruitment from other process errors in models for data-rich stocks. Estimates can also be used in the design of future simulation models and management strategy evaluations and in theoretical research regarding life history variation.

Sign in / Sign up

Export Citation Format

Share Document