Non-catfish families:
Macrouridae: body scaled; pectoral fins without spine; mouth not surrounded by barbels.
Ophidiidae: body scaled; pectoral and dorsal fins without spines.
Key to the marine species of Plotosidae occurring in the area
1a. Body very elongate, depth at first dorsal-fin origin less than 11% of standard length
(Fig. 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Euristhmus spp.1/
1b. Body less elongate, depth at first dorsal-fin origin usually greater than 15% of standard
length (Figs 3 and 4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ 2