Shortspine Thornyhead, Sebastolobus alascanus
The Shortspine Thornyhead, Sebastolobus alascanus, whose common Spanish name is chancharro alacrán, is a species in the Rockfishes and Scorpionfishes or Scorpaenidae Family, known collectively as escorpiónes or lapóns in Mexico. Globally, there are only three species in the genus Sebastolobus, of which two are found in Mexican waters, both in the Pacific.
The Shortspine Thornyheads have elongated bodies with a depth that is 24 to 28% of standard length. They have a red to orange-red coloration with white patches on their sides, back, cheeks, and spiny dorsal fin. Their gill chambers are light in color. Their dorsal fin has a dark spot posteriorly and black patches on its sides. They have a large head, cheeks with 8 to 10 strong spines, and a large terminal mouth. Their anal fin has 3 spines (the second being longer than the third) and 4 or 5 rays; their caudal fin is square; their dorsal fin has 15 to 18 spines (the third being shorter than the fourth) and 8 or 9 rays; their pectoral fins are strongly notched with 22 or 23 rays; and they have 18 to 23 gill rakers. Their body is covered with scales.
The Shortspine Thornyheads are bottom dwellers that reside in a wide variety of habitats including low hard relief, boulders and muddy bottoms and are found at depths between 60 and 5,000 feet. They reach a maximum length of 83 cm (33 inches), with females being larger than males. They are found as solitary individuals and are known to lay motionless on the bottom for long periods of time. They feed on other fish and invertebrates including amphipods and shrimp. Reproduction is oviparous with eggs being released in a gelatinous egg mass that is pelagic. They have a lifespan of up to one hundred years making them one of the longest living fish known. Very little is known about their behavioral patterns.
In Mexican waters the Shortspine Thornyheads are found from Magdalena Bay northward along the central and northwest coasts of Baja.
The Thornyheads can be distinguished from other Rockfish by the spiny ridges across their cheeks. They also have 15 or 16 dorsal spines while other Rockfish have 13. The Shortspine Thornyhead is similar to and found mixed in with the Longspine Thornyhead, Sebastolobus altivelis (elongated third dorsal spine).
The Shortspine Thornyheads are an expanding part of the California commercial fishery with fish taken primarily by deep water bottom trawls and the majority being exported to Japan. In domestic markets many are sold live as they lack a swim bladder and can survive after being hauled up from the deep. They are caught occasionally by recreational anglers but the equipment needed to reach their depth make them a poor sportsfish.