Obtaining a multiplicative bias calibration factor between the Africana with the old and the new trawl gear
Working Paper
2004
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University of Cape Town
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Abstract
The survey vessel Africana has been used for the demersal surveys on the south and west coasts of South Africa since 1984. In June 2003, the fishing gear used on this vessel was changed and a different value for the multiplicative bias factor q needs to be applied to the surveys conducted with the new gear in the assessments of the South African hake resource. Calibration experiments have been conducted between the Africana with the old gear (hereafter referred to as the “old Africana”) and the Nansen, and between the Africana with the new gear (“new Africana”) and the Nansen in order to provide a basis to relate the multiplicative biases of the Africana with the two types of gear ( qold and qnew ). A Generalised Linear Model (GLM) analysis assuming a negative binomial distribution for the catches made in the experiments has been applied to provide the calibration factor.
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Brandão, A., Rademeyer, R. A., & Butterworth, D. S. (2004). Obtaining a multiplicative bias calibration factor between the Africana with the old and the new trawl gear. MARAM: University of Cape Town.