Slender Suckerfish, Phtheirichthys lineatus
The Slender Suckerfish, Phtheirichthys lineatus, whose common Spanish name is rémora delgada, is a species in the Remora or Echeneidae Family, known collectively as remoras and pega pega in Mexico. Globally, this is only one species in the genus Phtheirichthys, and it is found in Mexican waters of both the Atlantic and the Pacific.
The Slender Suckerfish have very elongated bodies whose width is less than 10% of standard length. They are an overall dark blue color with three prominent light blue stripes along their flank. Their caudal fin is dark brown with narrow upper and lower white margins. Their anal and dorsal fins are transparent and their pectoral and pelvic fins are dark. Their head has a convex lower and a flat upper profile with mid-sized black eyes and a short disc that is 20 to 22% of standard length and reaches the center of the pectoral fins with nine to eleven lamellae. They have one to 3 gill rakers above and 14 to 17 below. Their lower jaw is projecting and their mouth is oblique with numerous small pointed teeth. Their anal and dorsal fins are of similar size and shape with very long bases that are approximately three times longer than the length of the head; their caudal fin margin is “W” shaped; their pectoral fins are pointed; and their pelvic fins are joined to the belly.
The Slender Suckerfish are oceanic pelagic fish that either travel attached to their hosts (large dead fish, slow moving fish, slow moving sharks, and turtles) or are free swimming. Due to their small disc, they are not as strongly host-dependent as the other Remoras for feeding and are known to consume planktonic crustaceans. They are normally found very close to the surface and range to depths up to 330 feet. They reach a maximum length of 76 cm (30 inches). Very little is known about their biology due to their need for fast moving water for survival, making study in captivity difficult.
In Mexican waters the Slender Suckerfish are found in all waters of the Pacific with the exception that they are absent from the northern 20% of the Sea of Cortez. They are more common in southern Mexican waters.
The Slender Suckerfish is an easy fish to identify due to its lamellae count and the stripes along its flank. It is, however, somewhat similar to the Whitefin Sharksucker, Echeneis neucratoides (18 to 28 disc plates, wide white bars on flanks).
The Slender Suckerfish are too rare to be of interest to most. They are most definitely a “catch-and-release”.
Slender Suckerfish, Phtheirichthys lineatus. Fish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, January 2010. Length: 15.5 cm (6.1 inches). Identification courtesy of H.J. Walker, Scripps Institution of Oceanography, La Jolla, CA.