Standardized CPUE of blue shark (Prionace glauca) caught by Indonesian longline fleet in the eastern Indian ocean

Standardized catch per unit effort (CPUE) as calculated based on commercial catches are the input data to run stock assessment models to gather useful information for decision making in fishery management. In this paper a Generalized Linear Model (GLM) was used to calculate relative abundance indices and effect of longline fishing gear configuration. The parameters used for standardization of CPUE were quarter, year, number of hooks between floats, latitude and longitude. Data were collected by a scientific observer program from August 2005 to December 2018. Most of the boats monitored were based in Benoa Port, Bali. Catches are often equal to zero because blue shark is a bycatch for Indonesian longline fleets. A tweedie model was selected because it has flexibility to the sample distributions. The results showed that the average scaled CPUE was 1.19. The CPUE pattern showed fluctuated during periods and reached the peak on 2006 with 2.09 and the lowest on 0.33 in 2011. The results from this study can demonstrate the catch variation of blue shark by Indonesian tuna longline fleets.