An initial analysis of the power of monitoring certain indices to determine the effect of fishing on penguin reproductive success from an experiment where pelagic fishing is prohibited in the neighbourhood of Robben Island, but continues around Dassen Island
| dc.contributor.author | Brandão, Anabela | |
| dc.contributor.author | Butterworth, Doug S | |
| dc.date.accessioned | 2016-03-16T06:51:44Z | |
| dc.date.available | 2016-03-16T06:51:44Z | |
| dc.date.issued | 2007 | |
| dc.date.updated | 2016-03-16T06:49:38Z | |
| dc.description.abstract | Historical data on fledging success and the breeders per adult moulter ratio for penguins at the Robben and Dassen island colonies are analysed using General Linear Modelling (GLM) to provide the basis for a simulation evaluation of the power of an experiment which closes a neighbourhood (about 20 km radius perhaps) around Robben Island to detect a statistically significant (5% level) impact of the (assumed multiplicative) effect of fishing on penguin reproductive output. Process error for each index is estimated to be about 20%. For an actual effect size of 30% (corresponding to a change in the population growth rate of about 3% p.a.), the experiment would have to continue for some 10 years for a better than 50:50 chance of such detection for the breeders per adult moulter index, and at least 20 years for fledging success. An initial GLM analysis to determine the direction and magnitude of the effect of pelagic catches on penguin reproductive output in terms of the two indices and colonies considered suggests that these catches enhanced this output in all four instances (a potential consequence of the hypothesis that fishing scatters large shoals, thus increasing the probability of natural predators finding their prey), though none of the estimates is statistically significant at the 5% level. | en_ZA |
| dc.identifier.apacitation | Brandão, A., & Butterworth, D. S. (2007). An initial analysis of the power of monitoring certain indices to determine the effect of fishing on penguin reproductive success from an experiment where pelagic fishing is prohibited in the neighbourhood of Robben Island, but continues around Dassen Island. http://hdl.handle.net/11427/17825 | en_ZA |
| dc.identifier.chicagocitation | Brandão, Anabela, and Doug S Butterworth "An initial analysis of the power of monitoring certain indices to determine the effect of fishing on penguin reproductive success from an experiment where pelagic fishing is prohibited in the neighbourhood of Robben Island, but continues around Dassen Island." (2007) http://hdl.handle.net/11427/17825 | en_ZA |
| dc.identifier.citation | Brandão, A., & Butterworth, D. S. (2007). An initial analysis of the power of monitoring certain indices to determine the effect of fishing on penguin reproductive success from an experiment where pelagic fishing is prohibited in the neighbourhood of Robben Island, but continues around Dassen Island. Unpublished report, Marine and Coastal Management, South Africa. Report No. EAFWG/OCT2007/STG/04. | en_ZA |
| dc.identifier.ris | TY - Journal Article AU - Brandão, Anabela AU - Butterworth, Doug S AB - Historical data on fledging success and the breeders per adult moulter ratio for penguins at the Robben and Dassen island colonies are analysed using General Linear Modelling (GLM) to provide the basis for a simulation evaluation of the power of an experiment which closes a neighbourhood (about 20 km radius perhaps) around Robben Island to detect a statistically significant (5% level) impact of the (assumed multiplicative) effect of fishing on penguin reproductive output. Process error for each index is estimated to be about 20%. For an actual effect size of 30% (corresponding to a change in the population growth rate of about 3% p.a.), the experiment would have to continue for some 10 years for a better than 50:50 chance of such detection for the breeders per adult moulter index, and at least 20 years for fledging success. An initial GLM analysis to determine the direction and magnitude of the effect of pelagic catches on penguin reproductive output in terms of the two indices and colonies considered suggests that these catches enhanced this output in all four instances (a potential consequence of the hypothesis that fishing scatters large shoals, thus increasing the probability of natural predators finding their prey), though none of the estimates is statistically significant at the 5% level. DA - 2007 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2007 T1 - An initial analysis of the power of monitoring certain indices to determine the effect of fishing on penguin reproductive success from an experiment where pelagic fishing is prohibited in the neighbourhood of Robben Island, but continues around Dassen Island TI - An initial analysis of the power of monitoring certain indices to determine the effect of fishing on penguin reproductive success from an experiment where pelagic fishing is prohibited in the neighbourhood of Robben Island, but continues around Dassen Island UR - http://hdl.handle.net/11427/17825 ER - | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11427/17825 | |
| dc.identifier.vancouvercitation | Brandão A, Butterworth DS. An initial analysis of the power of monitoring certain indices to determine the effect of fishing on penguin reproductive success from an experiment where pelagic fishing is prohibited in the neighbourhood of Robben Island, but continues around Dassen Island. 2007; http://hdl.handle.net/11427/17825. | en_ZA |
| dc.language | eng | en_ZA |
| dc.publisher | MARAM, University of Cape Town | en_ZA |
| 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.title | An initial analysis of the power of monitoring certain indices to determine the effect of fishing on penguin reproductive success from an experiment where pelagic fishing is prohibited in the neighbourhood of Robben Island, but continues around Dassen Island | en_ZA |
| dc.type | Journal Article | en_ZA |
| uct.type.publication | Research | en_ZA |
| uct.type.resource | Article | en_ZA |