Twobeak Searobin, Prionotus birostratus
The Twobeak Searobin, Prionotus birostratus, whose common Spanish name is vaca dospicos, is a species in the Searobin or Triglidae Family, known collectively as rubios and vacas in Mexico. Globally, there are twenty-three species in the genus Prionotus, fifteen of which are found in Mexican waters, ten in the Atlantic and five in the Pacific.
The Twobeak Searobins have rectangular block-like bodies that are gray brown in color with white undersides. Their large square bony head features large eyes and is covered with many ridges and spines. Their anal fin is transparent, their caudal fin has three dark bars; their first dorsal fin is dusky with the first three spines having dark tips; the second dorsal fin has dusky outter margins, and their pectoral fins are black with white blotches. The first dorsal fin has 10 spines and their second dorsal fin has 10 to 12 rays. They have flattened heads with two strongly projecting snout plates. There is a bony ridge under the eye and two spines at the rear of their eyes and five or six well-developed gill rakers. Their pectoral fins are long, reaching past the anal fin, and have shorter free rays. Their body is covered with very rough scales.
The Twobeak Searobins are found over and within sandy and muddy bottoms at depths between 60 and 200 feet. They are more active and feed at night; during the day they are found submerged in sand. They reach a maximum length of 18.0 cm (7.1 inches). The Twobeach Searobins are poorly studied and very little is known about their behavioral patterns.
In Mexican wates the Twobeak Searobin have a limited distribution being found from Magdalena Bay southward along the southwest coast of Baja, in the southern half of the Sea of Cortez, and along the coast of the mainland south to Guatemala.
The Twobeak Searobin can be confused with six other Searobins found in Mexican waters of the Pacific, however, its extended snout plates, aerodynamic body profile, and unique spotting pattern on the tail make it easy to identify.
Due to their bony structure and rarity, the Twobeak Searobins are of limited interest to most. They are a frequent by-catch of deepwater shrimp trawlers around the tip of Baja.