Updated GLM standardised CPUE abundance indices for orange roughy for known aggregations off Namibia from 1994 to 2006

Brandão, Anabela; Butterworth, Doug S

Updated GLM standardised CPUE abundance indices for orange roughy for known aggregations off Namibia from 1994 to 2006

Working Paper

2007

Publisher

University of Cape Town

Department

Marine Resource Assessment and Management Group

Faculty

Faculty of Science

Abstract

GLM analyses are used to standardise the CPUE data for Namibian orange roughy in a manner that deals with tows that record zero catch of orange roughy. The possibility of there being a “learning” period of lower CPUE for a new vessel when it enters the fishery is taken into account. Further, to allow for areal expansion of the fishery at each aggregation, sub-aggregations are defined and CPUE trends estimated separately for each. The “zero” method for combining the results for the various sub-aggregations to provide a single index for an aggregation is applied. The standardised CPUE value for 2005 (i.e. the July 2004 – June 2005 fishing year) for Johnies is the highest it has been in the last six years. The 2006 index is down from the previous year. For Frankies the 2006 index is up from that for 2004 (no 2005 index is available). No indices for Hotspot and Rix are available for the last two years.

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