Update on the CPUE standardization of the bigeye tuna caught by the Taiwanese large-scale tuna longline fishery in the Indian Ocean.

In the present study, the bigeye tuna catch and effort data from the logbook records of
the Taiwanese large-scale tuna longline fishing vessels operating in the Indian Ocean
from 2005-2021 were analyzed. We used cluster analysis to classify longline sets into
groups based on the species composition of the catch, to understand whether cluster
analysis could identify distinct fishing strategies. Bigeye tuna CPUE were then
standardized. CPUE Indices were estimated using two approaches, delta lognormal and
lognormal + constant, but the primary approach was the delta lognormal. All analyses
were performed using R source code developed in the Collaborative CPUE Workshop
applied to Taiwanese longline operational data. Standardized CPUE series of the bigeye
tuna caught by Taiwanese longline fishery showed a decreasing trend with smaller scale
in tropical region of Indian Ocean.