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Abstract

Round scad and Indian mackerel are considered the highly important speccies in the Gulf of Tonkin. During 2012-2017, total of 3 hydroacoustic surveys were conducted by using a multi-frequencies SIMRAD EK60 on board of M.V.SEAFDEC2, representative for the Southwest moonson (May 2012, June 2017) and the Northeast moonson (October 2012). The oceanographical condition in the Gulf of Tonkin during the surveys, including remote sensing data, in-situ measurements and plankton samples were collected and integrated with the relative abundance (sA) of Round scad and Indian mackerel. Generalized Additive Models (GAM) were used to finalise the best model for the Round scad and Indian mackerel in the Gulf of Tonkin. GAM showed that there was a tied relationship between oceanographical conditions and the relative abundance. It was found that DEP was the most important variables in the models for Round scad; then SST, Chlorophyll a and geographic velocity. SST and SSHa were considered the most contributed to the models of Indian mackerel; then the Chlorophyll a, geographic velocity and depth. These could contribute the scientific consideration for fishing ground forecast models of Round Scad and Indian mackerel in the Gulf of Tonkin and also whole marine waters of Vietnam.

Key words: Round scad; Indian mackerel; GAM; remote-sensing; oceanography; hydroacoustic.