Open AccessApplication of Fishery-independent Data as an Alternative Source for Determining Relative Abundance Indices of Blue Marlin, Makaira nigricans (Actinopterygii: Perciformes: Istiophoridae) in the North-eastern Indian Ocean
Author(s) -
Bram Setyadji,
D. Stott Parker,
Shengping Wang
Publication year - 2022
Publication title -
turkish journal of fisheries and aquatic sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.343
H-Index - 29
eISSN - 2149-181X
pISSN - 1303-2712
DOI - 10.4194/trjfas19142
Subject(s) - fishery , actinopterygii , perciformes , abundance (ecology) , geography , indian ocean , environmental science , oceanography , biology , geology , fish <actinopterygii>
The present study aimed to determine the abundance index of blue marlin, Makaira nigricans (Lacepède, 1802) utilizing fishery-independent data, i.e., scientific observer, and attempted to bridge the research's gap for low coverage information in the north eastern Indian Ocean. A total of 2,984 set-by-set observer data from 2006-2018, spatially disaggregated by one-degree blocks, were obtained from the Indonesian scientific observer program following commercial longline fleets. A delta-lognormal model was chosen to fit the dataset, using catch as the response variable with seven covariates. A backward procedure based on AIC, BIC and R2 were used to select the best model. Overall, the delta-Gamma performs better when modelling data with a high proportion of zeros than other traditional models. The blue marlin CPUE trend is relatively stable over time, despite the inter-annual fluctuations, which are likely a result of natural variation in the population as opposed to operational changes or inter-annual environmental variation. Given the low spatial coverage compared to logbook data, scientific observer data performed well and produced a robust abundance index of blue marlin in the northeastern Indian Ocean.