OpenUCT Home
→
Browsing by Author

Browsing by Author "Robinson, William M L"

Now showing items 1-20 of 31

Next Page

Analyses of the results from the island closure feasibility study for the Dassen/Robben and St Croix/Bird Island Pairs

Author: Robinson, William M L ; Butterworth, Doug S ; Furman, Liam B Date: 2014 The results from the Island Closure Feasibility Study are analysed using the GLMs as set out at the 2010 international stock assessment workshop. Estimates of residual variance for a random year effects GLM for the various penguin response ... Read more
An analysis of the small scale surveys of anchovy abundance around Robben and Dassen islands from 2009 to 2013

Author: Robinson, William M L ; Butterworth, Doug S Date: 2014 The results from the small scale hydroacoustic surveys of the abundance of anchovy around Robben and Dassen islands over the 2009-2013 period are analysed under the assumption of a Gaussian form for the trends in density at each island over ... Read more
Assessing the adequacy of current fisheries management under changing climate: a southern synopsis

Author: Plagányi, Éva E ; Weeks, Scala J ; Skewes, Tim D ; Gibbs, Mark T ; Blamey, Laura K ; Soares, Muri ; Robinson, William M L ; Poloczanska, Elvira S ; Norman-Lopez, Anna Date: 2011 Climate change is likely to have a significant impact on both target and non-target marine stocks worldwide, with the concomitant need for management strategies capable of sustaining fishing in future. We use several southern hemisphere ... Read more
Assessing the adequacy of current fisheries management under changing climate:a southern synopsis

Author: Plagányi, Éva E ; Weeks, Scala J ; Skewes, Tim D ; Gibbs, Mark T ; Blamey, Laura K ; Soares, Muri ; Robinson, William M L ; Norman-Lopez, Anna Date: 2012 Climate change is likely to have a significant impact on both target and non-target marine stocks worldwide, with the concomitant need for management strategies capable of sustaining fishing in future. We use several southern hemisphere ... Read more
Checking the penguin population model estimator for bias

Author: Robinson, William M L ; Butterworth, Doug S Date: 2010 A bootstrap approach is used to check the Robben Island penguin model estimator bias. The results show that there is little evidence for this. The distributions of estimates from the bootstrapping process are well-centred on the penalized maximum ... Read more
Comments on the benefit to penguins of fishing restrictions around Robben Island predicted by Weller et al. Robben Island penguin model simulations

Author: Robinson, William M L ; Butterworth, Doug S Date: 2014 The following comments relate to results in a recent publication (Weller et al., 2014) that are pertinent to the discussions of the Island Closure Task Team, specifically the impact of fishing around Robben Island on the penguin population. ... Read more
Ecosystem modelling provides clues to understanding ecological tipping points

Author: Plagányi, Éva E ; Ellis, Nick ; Blamey, Laura K ; Morello, Elisabetta B ; Norman-Lopez, Anna ; Robinson, William M L ; Sporic, Miriana ; Sweatman, Hugh Date: 2014 Ecological thresholds, associated with abrupt changes in the state and organisation of ecosystems, challenge both scientists and managers. Adaptive response to such changes, and planning for their occurrence, requires an understanding of the ... Read more
Evaluating the accuracy of hake abundance index predictions using different smoothing techniques

Author: Butterworth, Doug S ; Robinson, William M L ; Ross-Gillespie, Andrea Date: 2013 Alternative projection approaches based on linear and quadratic smoothing are applied retrospectively to abundance indices for hake to ascertain whether they can provide more accurate predictions of resource status one and two years ahead, ... Read more
Fitting both moult counts and tagging data to a population model for Robben Island penguins

Author: Robinson, William M L ; Butterworth, Doug S Date: 2009 A population model for penguins at Robben Island is fit to both moult count and tagresighting data. The fit is reasonable and provides an estimate of the over-dispersion of the resighting data. This is important for generating resightings in ... Read more
Full description of the Robben Island penguin-fish interaction model and base case Bayesian results

Author: Robinson, William M L ; Butterworth, Doug S Date: 2011 Work on the penguin–fish interaction model has progressed to the point where a reasonable base case for Robben Island has been achieved. Read more
Further results from future projections of a single or two sardine stock operating model, with initial results using a two-area directed sardine TAC

Author: De Moor, Carryn L ; Butterworth, Doug S ; Robinson, William M L Date: 2013 de Moor and Butterworth (2013a) showed some initial projections for future average directed catch and risk to the resources, assuming a no catch scenario, Interim OMP-13 v2, or a similar Management Procedure (MP) with re-tuned control parameters. ... Read more
GLMs relating penguin demographics to pelagic catches close to islands and to pelagic abundance

Author: Robinson, William M L ; Butterworth, Doug S Date: 2010 Earlier GLM analyses of the impact of pelagic fishing in the vicinities of Robben and Dassen Islands on the dynamics of penguins breeding on those islands are extended to cover a wider set of data series, and to consider relationships involving ... Read more
Illustrative outputs of the age-structured model of African penguin populations for linking to the pelagic OMP testing process

Author: Robinson, William M L ; Plagányi, Éva E ; Butterworth, Doug S Date: 2008 Given the move towards adopting an ecosystem approach to fisheries in the pelagic sector, the new joint OMP needs to be tested in the light of not only the risk parameters as considered previously, along with catch statistics, but also ... Read more
Island closure feasibility study power analysis

Author: Robinson, William M L ; Butterworth, Doug S Date: 2014 This paper indicates how it is planned to extend the general linear model (GLM) analyses by Robinson (2013) to estimate the power of the Island Closure Experiment. Statistical power reflects the probability that an experiment will detect ... Read more
Island closure feasibility study power analysis results for Dassen and Robben islands

Author: Robinson, William M L ; Butterworth, Doug S Date: 2014 The power analysis for penguin responses to fishing around Dassen and Robben islands has been completed. Response variables considered are chick condition, active nest proportion, fledging success, chick growth, foraging path length, ... Read more
Penguin island closure feasibility study analysis results update: random effects models applied to both Western and Eastern Cape islands

Author: Robinson, William M L ; Butterworth, Doug S Date: 2014 This Addendum updates results from previous papers using random effects instead of fixed effects models for the year factors. Results are now given for Bird and St Croix islands in addition to those for Dassen and Robben islands. The results ... Read more
Penguin model update: an improved penguin mortality relationship with sardine biomass and results of sensitivities to the base case

Author: Robinson, William M L ; Butterworth, Doug S Date: 2011 Work on the penguin–fish interaction model has progressed to the point where a candidate base case for Robben Island was presented in document FISHERIES/2011/SWG–PEL/40. However, one concern there was that the likelihood could always be ... Read more
Penguin population models for Robben Island

Author: Robinson, William M L ; Butterworth, Doug S Date: 2010 As an initial illustrative exercise, a population model for Robben Island penguins, which includes dependency of reproductive success and survival rate on pelagic fish abundance, is fitted to moult count information for the colony. The ... Read more
Penguin survival estimates from tag data using a multinomial likelihood

Author: Robinson, William M L ; Butterworth, Doug S Date: 2010 A simple population model for Robben Island penguins is considered which incorporates fitting to both moult counts and tag data. The latter are now fit using a multinomial likelihood which is the method used in program MARK. Probability intervals ... Read more
Projections of the Robben Island African penguin population

Author: Robinson, William M L ; Butterworth, Doug S Date: 2012 The Robben Island penguin population model was described in the working group document FISHERIES/2012/JUL/SWG–PEL/35. This paper shows projected penguin numbers under various scenarios concerning the future abundance and distribution of sardine. Read more

Now showing items 1-20 of 31

Next Page

Browse

All of OpenUCT