Giant Kelpfish, Heterostichus rostratus
Giant Kelpfish, Heterostichus rostratus. Fish caught from coastal waters off San Diego, California, November 2018. Length: 16 cm (6.3 inches). Catch, photograph and identification courtesy of Ben Cantrell, San Diego, California.
Giant Kelpfish, Heterostichus rostratus. Fish caught from within the Avalon Marina, San Clemente Island, Avalon, California, December 2022. Length: 20 cm (7.9 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.
Giant Kelpfish, Heterostichus rostratus. Fish caught from within Mission Bay, San Diego, California, March 2020. Length: 25 cm (9.8 inches). Catch, photograph and identification courtesy of Chris Moore, Peoria, Arizona.
Giant Kelpfish, Heterostichus rostratus. Fish caught from coastal waters off San Diego, California, March 2020. Length: 29 cm (12 inches). Catch, photograph and identification courtesy of Chris Moore, Peoria, Arizona.
Giant Kelpfish, Heterostichus rostratus. Fish caught from coastal waters off San Diego, California. Length: 30 cm (12 inches). Catch, photograph and identification courtesy of George Brinkman, Guelph, Ontario, Canada.
Giant Kelpfish, Heterostichus rostratus. Underwater photograph taken in coastal waters off Mission Bay, San Diego, California, September 2016. Photograph courtesy of Bob Hillis, Ivins, Utah.
Giant Kelpfish, Heterostichus rostratus. Underwater photograph taken in coastal waters off Mission Bay, San Diego, California, September 2017. Photograph courtesy of Bob Hillis, Ivins, Utah.
The Giant Kelpfish, Heterostichus rostratus, is a member of the Kelp Blenny or Clinidae Family, and is known in Mexico as sargacero gigante. This is the only global species in the genus Heterostichus and it is found only in Mexican waters of the Pacific Ocean.
The Giant Kelpfish has an elongated and compressed body. They are cryptically colored and have three different morphologies, brown, green and red, that closely match their surrounding plant habitat. They also have 4 different dark melanin patterns which appear to be superimposed and can change rapidly. Their head is elongated and pointed with a small terminal mouth and modest-sized eyes. Their anal fin has 2 spines and 31 to 35 rays; their caudal fin is deeply forked; their dorsal fin has 33 to 38 spines and 11 to 13 rays; their pectoral fins have 12 to 14 rays; and, their pelvic fins have 1 spine and 3 rays. They have 5 to 7 gill rakers on the upper arch and 12 or 13 gill rakers on the lower arch.
Giant Kelpfish are found in rocky areas with kelp forests and surrounding plant from the intertidal zone to depths up to 40 m (132 feet). They reach a maximum of 61 cm (2 feet 0 inches) in length with females being larger and living longer than males. They feed on small crustaceans, small fish, and mollusks. They are found associated with a large number of different plant species as they have the ability to change colors to match their surroundings. Reproduction is oviparous with females depositing eggs into algal nests which are vigorously guarded by males for up to two weeks until they hatch. They are well-developed upon hatching and remain in the planktonic stage in schools within the kelp forest for several weeks. Juveniles develop coloration and become solitary moving to nearshore algae. They have lifespans of 5 years. The Giant Kelpfish 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 Giant Kelpfish is a resident of Mexican waters of the Pacific Ocean but have a limited distribution being found in abundance from Magdalena Bay, Baja California Sur, northward along the central and northwest coasts of Baja.
The Giant Kelpfish is very similar to, and can be easily confused with, the Crevice Kelpfish, Gibbonsia montereyensis, the Spotted Kelpfish, Gibbonsia elegans, and the Striped Kelpfish, Gibbonsia metzi, however, all three have rounded caudal fins.
From a conservation perspective the Giant Kelpfish is currently considered to be of Least Concern with stable, widely distributed populations. They are retained by subsistence fishermen for human consumption and by the aquarium trade on a limited basis.