Hourglass Clingfish, Tomicodon petersii

Hourglass Clingfish, Tomicodon petersii. Underwater photographs taken in Zihuantanejo Bay, Guerrero, January 2019 and February 2023. Photographs courtesy of Ron Woheau, Zihuantanejo.

The Hourglass Clingfish, Tomicodon petersii, is member of the Clingfish or Gobiesocidae Family, that is also known as Peter’s Clingfish, and in Mexico as chupapiedras clepsidra. Globally, there are twenty-two species in the genus Tomicodon, of which six are found in Mexican waters, all in the Pacific Ocean.

The Hourglass Clingfish has an elongated “tadpole” like body that have relatively slender head when compared to other Clingfish. They are white dorsally with brown reticulum that thicken in places to form a series of irregular “hourglass” bars and the flanks have elongated spots and a prominent dark brown spot above the pectoral fins. Their anal fin has 6 or 7 rays; their caudal fin has 8 to 10 rays; their dorsal fin has 7 or 8 rays; and, their pectoral fins have 19 to 21 rays. The sucker on their ventral side is disproportionately large and further from the anus than to the anal fin origin. Their skin is smooth and has no scales.

The Hourglass Clingfish is a shallow-water species found in rocky areas within tidal pools at depths up to 5 m (15 feet). They reach a maximum length of 4.6 cm (1.8 inches). They feed primarily on barnacles and small crustaceans. The Hourglass Clingfish is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

The Hourglass Clingfish is a resident of all Mexican waters of the Pacific Ocean with the exception that they are absent from Magdalena Bay, Baja California Sur, northward along the central and northwest coasts of Baja and from the extreme northern portions of the Sea of Cortez.

The Hourglass Clingfish is most likely confused with the Blackstripe Clingfish, Tomicodon myersi (lacks vertical bars).

From a conservation perspective the Hourglass Clingfish is currently considered to be of Least Concern with stable widely distributed populations. They are too small to be of interest to most.