Smiling Sand Eel, Ichthyapus selachops
The Smiling Sand Eel, Ichthyapus selachops, whose common Spanish name is tieso sonriente, is a species in the Snake Eel or Ophichthidae Family, known collectively as tiesos in Mexico. Globally, there are only five species in the genus Ichthyapus, two of which are found in Mexican waters, one in the Atlantic and one in the Pacific.
The Smiling Sand Eels have elongated cylindrical bodies with a rounded cross-section that is fusiform (tapering at both ends). They have an overall creamy yellow coloration with irregular brown spots on their head and a brown stripe along their mid-side. Their head is conical with a sharply pointed snout that is broad, depressed, and overhanging. They have minute eyes and pointed teeth in a single row. Their front nostril is a flat hole (a key to identification) and their rear nostril has an irregular rim and opens into the mouth. Their gill openings are below the head on the throat. They do not have fins or scales. Their long tail is 62 to 64% of total length and ends in a hard finless point.
The Smiling Sand Eels are demersal burrowing fish that spend the majority of their time half submerged within soft sandy and muddy bottoms at depths up to 100 feet. They reach a maximum length of 54 cm (21 inches). They feed on invertebrates and small fish. They are seldom seen by humans and very little is known about their behavioral patterns.
In Mexican waters the Smiling Sand Eels have a limited distribution being found along the extreme southwest corner of the Baja, as established by the fish photographed below, along the east coast of Baja from Santa Rosalia to Cabo San Lucas, and along the coast of the mainland from Mazatlán to Guatemala.
The Smiling Sand Eel is virtually identical to and very easily confused with the Equatorial Eel, Apterichtus equatorialis (maximum length 30 cm; tubular front nostril; rear nostril is a slit in lip).
The Smiling Sand Eels are too rare to be of interest to most.
Smiling Sand Eel, Ichthyapus selachops. Fish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, May 2013. Length: 31 cm (12 inches). Tail 61%. Identification courtesy of H.J. Walker, Jr., Scripps Institution of Oceanography, La Jolla, CA.