Rosethorn Rockfish, Sebastes helvomaculatus
Rosethorn Rockfish, Sebastes helvomaculatus. Fish caught from coastal waters off Tijuana, Baja California, October 2016. Length: 15.2 cm (6.0 inches). Catch, photograph, and identification courtesy of Eli (obsessiveangling.wordpress.com).
The Rosethorn Rockfish, Sebastes helvomaculatus, is a member in the Rockfish and Scorpionfish or Scorpaenidae Family, and is known in Mexico as rocote moteado. Globally, there are one hundred eight species in the genus Sebastes, of which fifty-three are found in Mexican waters, all in the Pacific Ocean.
The Rosethorn Rockfish has a small elongated body with a depth that is 28% to 32% of standard length. They vary in color from crimson, orange, yellow or yellowish-green arranged in a series of diffuse stripes. Their anal and dorsal fins are usually striped in pink or green and the top of their head may be green with white stripes. They have 4 or 5 white blotches on their back. Their anal spines are shorter than, or equal in length to, the anal rays. Their head is relatively narrow and spine-laden with a short pointed snout, large eyes, and a small terminal mouth. Their anal fin has 3 spines and 5 to 7 rays; their caudal fin is square; their dorsal fin has 12 to 14 spines and 12 to 14 rays; and their pectoral fins have 15 to 18 rays. They have 27 to 33 gill rakers.
The Rosethorn Rockfish is a demersal species that is found in benthic environments over mixed rock and mud substrate at depths between 79 m (260 feet) and 350 m (1,150 feet) with water temperatures that can be as low as 4.1oC (39oF). They are typically solitary or found in small aggregations. They reach a maximum of 43 cm (17 inches) in length and of 1.5 kg (3 lbs 5 oz) in weight. As of January 1, 2023, the International Game Fish Association world record stood at 1.49 kg (3 lbs 4 oz) with the fish caught in coastal waters off Elrington Island, Alaska in July 2004. They feed on a wide variety of invertebrates and small fish. In turn they are preyed upon by Lingcod and Yelloweye Rockfish. Reproduction is oviparous with pelagic eggs. They have a lifespan of up to eighty-seven years. The Rosethorn Rockfish 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 Rosethorn Rockfish is a resident of Mexican waters of the Pacific Ocean but has a limited distribution being found from Guerrero Negro, Baja California northward along the central and northwest coasts of Baja.
The Rosethorn Rockfish is most likely confused with the Pinkrose Rockfish, Sebastes simulator (bright red or red with yellow tinges; 17 or more pectoral rays), the Rosy Rockfish, Sebastes rosaceus (purple on head, back, and sides), and the Swordspine Rockfish, Sebastes ensifer (extended second anal spine).
From a conservation perspective the Rosethorn Rockfish has not been formally evaluated. They are not an important commercial food fish. They are caught as a by-catch of trawl and longline fisheries as well as by deep water recreational anglers are retained for human consumption.