Analyses of the results from the island closure feasibility study for the Dassen/Robben and St Croix/Bird Island Pairs
| dc.contributor.author | Robinson, William M L | |
| dc.contributor.author | Butterworth, Doug S | |
| dc.contributor.author | Furman, Liam B | |
| dc.date.accessioned | 2016-03-22T09:28:42Z | |
| dc.date.available | 2016-03-22T09:28:42Z | |
| dc.date.issued | 2014 | |
| dc.date.updated | 2016-03-22T07:41:40Z | |
| dc.description.abstract | 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 variables are considered to be sufficiently precise to enable power analyses to be conducted to contribute to the evaluation of whether to transition to a full experimental closures programme, so that the feasibility study may be considered successfully concluded. For the Dassen and Robben Islands about 80% of the estimates of the fishing effect parameter λ are positive, with this same proportion maintained for those (about one sixth) of these estimates which are significant at the 5% level. Thus the preponderance of the evidence from these analyses is that the impact of fishing around these islands has been positive. The rather fewer instances available to analyse for the Eastern Cape colonies suggest a weakly positive effect at Bird Island, but a somewhat stronger negative effect at St Croix. The power analyses suggest that in cases for Dassen and Robben Islands where further data collection might render currently non-significant λ estimates significant at the 5% level within the next two decades, the likely period required for such further collection would typically be in the vicinity of five years. The advantage provided by continuing the closure programme itself seems however to be slight, as the natural variation over time in normal catches would be sufficient to provide the contrast to achieve such results with only typically two years’ extension to those five years. For the two Eastern Cape islands, it seems that results which are statistically significant at the 5% level seem unlikely to be achieved in the foreseeable future – a result which may be a consequence of the relatively low levels of sardine catches typically taken close to those islands. | en_ZA |
| dc.identifier.apacitation | Robinson, W. M. L., Butterworth, D. S., & Furman, L. B. (2014). <i>Analyses of the results from the island closure feasibility study for the Dassen/Robben and St Croix/Bird Island Pairs</i> University of Cape Town ,Faculty of Science ,Marine Resource Assessment and Management Group. Retrieved from http://hdl.handle.net/11427/18153 | en_ZA |
| dc.identifier.chicagocitation | Robinson, William M L, Doug S Butterworth, and Liam B Furman <i>Analyses of the results from the island closure feasibility study for the Dassen/Robben and St Croix/Bird Island Pairs.</i> University of Cape Town ,Faculty of Science ,Marine Resource Assessment and Management Group, 2014. http://hdl.handle.net/11427/18153 | en_ZA |
| dc.identifier.citation | Robinson, W. M. L., Butterworth, D. S., & Furman, L. B. (2014). Analyses of the Results from the Island Closure Feasibility Study for the Dassen/Robben and St Croix/Bird Island Pairs. | en_ZA |
| dc.identifier.ris | TY - Working Paper AU - Robinson, William M L AU - Butterworth, Doug S AU - Furman, Liam B AB - 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 variables are considered to be sufficiently precise to enable power analyses to be conducted to contribute to the evaluation of whether to transition to a full experimental closures programme, so that the feasibility study may be considered successfully concluded. For the Dassen and Robben Islands about 80% of the estimates of the fishing effect parameter λ are positive, with this same proportion maintained for those (about one sixth) of these estimates which are significant at the 5% level. Thus the preponderance of the evidence from these analyses is that the impact of fishing around these islands has been positive. The rather fewer instances available to analyse for the Eastern Cape colonies suggest a weakly positive effect at Bird Island, but a somewhat stronger negative effect at St Croix. The power analyses suggest that in cases for Dassen and Robben Islands where further data collection might render currently non-significant λ estimates significant at the 5% level within the next two decades, the likely period required for such further collection would typically be in the vicinity of five years. The advantage provided by continuing the closure programme itself seems however to be slight, as the natural variation over time in normal catches would be sufficient to provide the contrast to achieve such results with only typically two years’ extension to those five years. For the two Eastern Cape islands, it seems that results which are statistically significant at the 5% level seem unlikely to be achieved in the foreseeable future – a result which may be a consequence of the relatively low levels of sardine catches typically taken close to those islands. DA - 2014 DB - OpenUCT DP - University of Cape Town KW - results KW - feasibility study KW - Robben Island KW - Dassen Island KW - St Croix LK - https://open.uct.ac.za PB - University of Cape Town PY - 2014 T1 - Analyses of the results from the island closure feasibility study for the Dassen/Robben and St Croix/Bird Island Pairs TI - Analyses of the results from the island closure feasibility study for the Dassen/Robben and St Croix/Bird Island Pairs UR - http://hdl.handle.net/11427/18153 ER - | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11427/18153 | |
| dc.identifier.vancouvercitation | Robinson WML, Butterworth DS, Furman LB. Analyses of the results from the island closure feasibility study for the Dassen/Robben and St Croix/Bird Island Pairs. 2014 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/18153 | en_ZA |
| dc.language.iso | eng | |
| dc.publisher.department | Marine Resource Assessment and Management Group | en_ZA |
| dc.publisher.faculty | Faculty of Science | en_ZA |
| dc.publisher.institution | University of Cape Town | |
| dc.subject | results | en_ZA |
| dc.subject | feasibility study | en_ZA |
| dc.subject | Robben Island | en_ZA |
| dc.subject | Dassen Island | en_ZA |
| dc.subject | St Croix | en_ZA |
| dc.title | Analyses of the results from the island closure feasibility study for the Dassen/Robben and St Croix/Bird Island Pairs | en_ZA |
| dc.type | Working Paper | en_ZA |
| uct.type.filetype | Text | |
| uct.type.filetype | Image | |
| uct.type.publication | Research | en_ZA |
| uct.type.resource | Research paper | en_ZA |