Standardising the CPUE for the <Emphasis Type="Italic">Illex argentinus</Emphasis> fishery in the Southwest Atlantic |
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Authors: | Chih-Shin Chen Tai-Sheng Chiu |
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Institution: | (1) Institute of Marine Affairs and Resource Management, National Taiwan Ocean University, Keelung, 20224, Taiwan;(2) Institute of Zoology, Department of Life Science, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan |
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Abstract: | The catch per unit effort (CPUE) is a widely used index for assessing the abundance of exploited populations in fishery management.
To obtain appropriate CPUE values, it is essential to standardise catch-effort data from fisheries. This task is particularly
important for squid fisheries because squid generally have a short life-span and are vulnerable to environmental variability,
and thus effective fishery management should take such factors into account. In this study, we analysed unit catches of paired
vessels operating under similar fishing conditions to calculate their relative fishing power (RFP) in order to standardise
the CPUE of the Taiwanese fleet jigging for Illex argentinus in the Southwest Atlantic. To evaluate the appropriateness of the method, we used a logbook dataset covering eleven years
(1993–2003), in which 93.5% of the total catch during the period was included. The results indicate that 98.7% of the fishing
effort can be standardised according to the estimated RFP. Compared to nominal CPUE, the standardised CPUE values projected
an explainable temporal pattern, indicating an increasing trend in abundance from 1995 to 1999 and a subsequent sharp plunge
from 1999 to 2003. However, the RFP was not related to apparent physical factors of the vessel, such as gross tonnage or vessel
length. Our evaluations suggest that the RFP method is appropriate for standardising the CPUE, so that it can serve as an
abundance index that reflects the annual recruitment size of the squid fishery, because the quality of the method can potentially
take possible affecting factors into account in order to satisfy the general assumptions of standardisation criteria. However,
the effects of varying the settings of parameters should be carefully examined prior to applying this standardisation method
to other squid fisheries. |
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Keywords: | CPUE Illex argentinus Squid fishery Standardisation Stock |
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