Enables beta-galactoside (CMP) alpha-2,3-sialyltransferase activity. Involved in ganglioside biosynthetic process via lactosylceramide and protein glycosylation. Predicted to be located in Golgi membrane. Orthologous to human ST3GAL2 (ST3 beta-galactoside alpha-2,3-sialyltransferase 2). [provided by Alliance of Genome Resources, Apr 2022]