Pacific Portholefish, Diplophos taenia
The Pacific Portholefish, Diplophos taenia is a species in the Bristlemouth or Gonostomatidae Family. This fish does not have a Spanish name. It received its common name from first be observed out of a porthole in a ship. Globally, there are only five species in the genus Diplophos, one which one, this species, that is found in Mexican waters of both the Atlantic and the Pacific.
The Pacific Portholefish have very slender elongated bodies that taper significantly from head to tail. They are uniformly dull grayish brown in color and transition to silver ventrally. Their fins are transparent. Their head is large with a pointed snout, mid-sized eyes, and a large mouth that extends to the rear margin of the eyes. Their anal fin has no spines and 59 to 72 rays; their caudal fin is small and forked; and their dorsal fin has 10 or 11 rays and no spines. They have two conspicuous rows of photophores (light producing organs) that run ventrally from their head to the base of their tail. Reproduction is oviparous with planktonic eggs and larvae. They are a rare and poorly studied species and very little is known about their behavioral patterns.
The Pacific Portholefish are a bathypelagic species found over sandy bottoms. They reach a maximum length of 28 cm (11 inches). They are vertical migrators that move toward the surface during the night to feed on plankton and return to depths of at least 2,500 feet during the day to avoid predation.
The Pacific Portholefish is a global species found in all tropical and subtropical seas from 40oN latitude to 30oS latitude and is found in all Mexican waters of the Atlantic and the Pacific.
The Pacific Portholefish is difficult to identify. A correct identification requires a professional ichthyologist that specializes in Stomiiformes, the deep water dragonfish, hatchetfish, lightfish, loosejaws, and viperfish. I am fortunate to have had productive discussions with Cindy Klepadio, Scripps Institution of Oceanography, La Jolla, California about this fish which is currently a part of the SIO Fish Collection.
The Pacific Portholefish are relatively small, exceedingly rare, and of limited interest to most.
Pacific Portholefish, Diplophos taenia. Fish caught from coastal waters off Point Palmilla, Baja California Sur, February 2014. Regurgitated by a Highfin Sand Perch, Diplectrum labarum. Length: 8.5 cm (3.3 inches). Identification courtesy of Cindy Klepadio, Scripps Institution of Oceanography, La Jolla, CA.