Kelp Perch, Brachyistius frenatus
Kelp Perch, Brachyistius frenatus. Fish caught from coastal waters off Catalina Island, California, December 2020. Length: 18 cm (7.1 inches). Catch, photograph, and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.
Kelp Perch, Brachyistius frenatus. Underwater photograph taken in the coastal waters off Monterey, California, February 2022. Photograph and identification courtesy of Bob Hillis, Ivins, Utah.
Kelp Perch, Brachyistius frenatus. Fish caught from within the Puget Sound, Des Moines, Washington, November 2020. Length: 20 cm (7.9 inches). Catch, photographs and identifications courtesy of Luke Ovgard, Klamath Falls, Oregon.
Kelp Perch, Brachyistius frenatus versus Striped Seaperch, Embiotoca lateralis. Both fish caught from within the Puget Sound, Des Moines, Washington, November 2020. Catch, photographs and identifications courtesy of Luke Ovgard, Klamath Falls, Oregon.
The Kelp Perch, Brachyistius frenatus, is a member of the Surfperch or Embiotocidae Family, and is also known at the Kelp Surfperch and the Brown Sea-perch and in Mexico as h and in Mexico as perche de varech. Globally, there are two species in the genus Brachyistius, both of which are found in Mexican waters of the Pacific Ocean.
The Kelp Perch have highly compressed elongated body with a depth that is 33% to 37% of standard length. Dorsally they are golden-brown to reddish transitioning to tan ventrally and lack barring and stripes. Their scales are trimmed in black with the color being more prominent above the lateral line. They have a transparent line that runs through the eye, breaks, and then continues before breaking to spots and continuing into the caudal fin. Their fins are pale or rosy. Their head has a sharply upturned small terminal mouth and pointed snout with a projecting upper jaw. Their anal fin has 3 or 4 spines and 20 to 25 rays; their caudal fin is forked; their first dorsal fin has 7 to 10 spines; their second dorsal fin has 13 to 16 rays; and, their pectoral fins have 17 or 18 rays. They have 24 to 29 gill rakers of which 17 to 20 are on the lower. Their body is covered with large scales.
The Kelp Perch is found within the canopies of Giant Kelp Beds, Macrocystis pyrifera, large algae, eelgrass, and surfgrass over boulders and sand substrate from the intertidal zone to depths up to 76 m (250 feet). They are found as solitary individuals or in small groups and in large groups during the summer. The juveniles are found in larger aggregations and higher in the canopy than adults. They reach a maximum of 22 cm (8.5 inches) in length and 0.13 kg (5 oz) in weight. The juveniles consume zooplankton including cladocerans, copepods, larval crustaceans, fish eggs and ostracods; the adults consume benthic gammarid and caprellid amphipods, bryozans, polychaetes, small snails, and shrimps. They act as cleaner fish removing external parasites from a wide variety of larger fishes. In turn they are preyed upon by Copper Rockfish, Giant Kelpfish, Pacific Bonito, various sea birds and sea lions. Reproduction is viviparous with internal fertilization with each female having the ability to store sperm producing 3 to 50 young annually that are born live at 3.3 cm (1.3 inches) in length in the spring. They are subject to die offs in water temperatures below 8oC (46oF). They have lifespans of three years.
The Kelp Perch is a resident of Mexican waters of the Pacific Ocean but has a limited distribution being found only from Guerrero Negro, Baja California, northward along the central and northwest coasts of Baja.
The Kelp Perch, being a uniform dark brown color, can be easily identified from other surfperches including Redtail Surfperch, Amphistichus rhodoterus and the Shiner Perch, Cymatogaster aggregate (both of which have distinct barring), and the Striped Seaperch, Emboiotoca lateralis (distinct stripes).
From a conservation perspective the Kelp Perch is currently considered to be Data Deficient. There populations are strongly affected but the abundance of Giant Kelp whose abundance undergoes dramatic reductions during warm-water El Niño events. They are also killed by kelp-harvesting machines. The Kelp Perch is small in stature and of limited interest to most. Historically they were an important food source of Native Americans. They are utilized by the aquarium trade at a modest level.