Docosahexaenoic acid (DHA, 22:6n-3) and ecosapentaenoic acid (20:5n-3) have attracted increasing attention since the first epidemiological report on the importance of n-3 essential fatty acids. It is thought that DHA has important functions in brain and retinal tissues. Thraustochytrids, a group of marine protists, are capable of heterotrophic growth, and are potential omega-3 producers for industrial use, especially the members of the Schizochytrium and Thraustochytrium genera. The aims of this work were to isolate, identify and screen thraustochytrids from 17 different locations. Twenty-three isolates were screened for biomass, total fatty acid (TFA) and DHA content. Analysis of the fatty acid methyl esters revealed four distinct clusters biomass ranged from $8.68-9.36gL^{-1}$, and lipid and DHA contents ranged from $3.11-4.10gL^{-1}$ and $1.05-1.93gL^{-1}$ biomass, respectively. B-12 isolates were screened for biomass ($9.36gL^{-1}$), TFA ($4.10gL^{-1}$) and DHA (47.01%, w/w) content. C-6 isolates were also screened for biomass ($8.92gL^{-1}$), TFA ($3.30gL^{-1}$) and DHA (49.41%, w/w) content. The 18S rRNA gene sequencing results identified Schizochytrium mangrovei as B-12 and Crypthecodium cohnii as C-6.