Update on CPUE Standardization of Blue Marlin (Makaira nigricans) from Indonesian Tuna Longline Fleets 2006-2021

Black marlin (Makaira indica) is commonly caught as frozen by-catch from Indonesian tuna longline fleets
targeting albacore, yellowfin and bigeye tuna and its contributed around 7% (~600 tons/year). Relative
abundance indices as calculated based on commercial catches are the input data for several to run stock
assessment analyses that provide models to gather information useful information for decision making and
fishery management. In this paper a Delta-Lognormal Model (GLM) was used to standardize the catch per
unit effort (CPUE) and to calculate estimate relative abundance indices based on the Indonesian longline
dataset. Data was collected from August 2005 to December 2021 through scientific observer program. Most
of the vessels monitored were based in Benoa Port, Bali. The result showed that year, quarter, latitude and
longitude statistically significant and kept in the lognormal model, whereas moon and cluster were excluded.
In addition, according to the delta model, targeting effect (cluster) and vertical movement (latitude) played
no part on the possibility of catching BUM. Whereas, longitude, year, quarter, and the presence of moon
phase were likely the more influential effects. However, high uncertainties seemed as lingering issue, which
is inevitable due to low coverage of scientific observer data.