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The Shortspine Thornyhead (Sebastolobus alascanus) is a deep-sea scorpaenid fish characterized by its robust body, large head, and prominent spines. It is a commercially important species in many parts of its range, particularly in the North Pacific. Its common name refers to the relatively shorter spines on its head compared to its congener, the Longspine Thornyhead (Sebastolobus altivelis). This species is well-adapted to its deep-water, benthic habitat.
Physical Characteristics
- Body shape
- compressed
- Coloration
- Typically reddish-orange to reddish-brown dorsally, fading to pink or whitish ventrally. Fins often have darker blotches or margins. Juveniles may exhibit more mottled patterns.
- Scale type
- ctenoid
- Mouth position
- terminal
- Distinctive features
- Large head with numerous prominent spines and ridges, particularly on the operculum and preoperculum., Large eyes, adapted for low light conditions., A deep notch in the dorsal fin between the spiny and soft-rayed portions., Pectoral fins are large and fan-like, often with a dark blotch at the base., The third dorsal spine is typically the longest, but shorter than the longest soft ray., The second anal spine is stout and longer than the third.
- Dorsal fin
- Single dorsal fin with a deep notch, typically 15-17 strong spines followed by 8-9 soft rays. The third dorsal spine is usually the longest.
- Tail fin
- Truncate to slightly emarginate caudal fin.
- Pectoral fin
- Large, fan-like pectoral fins with 20-24 rays, often extending beyond the anus.
- Distinctive fins
- Pelvic fins thoracic, with 1 spine and 5 soft rays. Anal fin with 3 spines and 4-5 soft rays; the second anal spine is notably robust and longer than the third.
Identification Tips
Head Spines
Count the number and observe the prominence of spines on the head, particularly on the preoperculum and operculum. Shortspine Thornyhead has fewer and relatively shorter spines compared to Longspine Thornyhead.
Dorsal Fin Spines
Examine the dorsal fin. The third dorsal spine is typically the longest, but it is shorter than the longest soft ray. This distinguishes it from Longspine Thornyhead where the third dorsal spine is longer than the longest soft ray.
Anal Fin Spines
Note the relative lengths of the anal fin spines. The second anal spine is stout and distinctly longer than the third in S. alascanus.
Pectoral Fin Rays
Count the pectoral fin rays (typically 20-24). The presence of a dark blotch at the base of the pectoral fin is also a helpful indicator.
Coloration
Observe the overall reddish-orange to reddish-brown coloration, which can vary with depth and individual.
Habitat
- Water type
- saltwater
- Depth
- Typically found at depths ranging from 150 to 1,500 meters (500 to 4,900 feet), with a common range of 200-800 meters.
- Environment
- Benthic, inhabiting soft bottoms (mud, sand, gravel) on continental slopes and shelves. They are often associated with rocky outcrops and canyons.
- Geographic range
- North Pacific Ocean, from the Bering Sea and Aleutian Islands south along the North American coast to Baja California, Mexico. Also found off the coast of Japan and the Okhotsk Sea.
Aquarium Information
- Care level: expert
- Temperament: territorial
- Diet: carnivore
- Minimum tank size: Not suitable for home aquaria due to deep-sea requirements and size.
- Temperature: 2-6°C (35-43°F)
- pH level: 7.8-8.2
- Hardness: High (marine salinity)
- Compatibility: Not compatible with other species in an aquarium setting due to specialized deep-sea requirements and predatory nature.
- Special requirements: Requires specialized deep-sea pressure and temperature conditions, making it unsuitable for typical aquarium environments. Maintaining such conditions is extremely challenging and costly.
Wild Information
- Conservation status: least concern
- Seasonality: Fished year-round, but specific seasons may have higher catch rates depending on regional regulations and fish availability.
- Market price: Varies by region and market demand, generally moderate to high due to its deep-water origin and desirable flesh.
- Commercial importance: high
- Taste: Mild, sweet, and delicate
- Texture: Firm, flaky, and moist
- Cooking methods: Baking, Steaming, Grilling, Frying, Sashimi
- Nutritional value: Good source of lean protein, omega-3 fatty acids, and essential vitamins and minerals.
Key Facts
Deep-Sea Dwellerbehavior
Shortspine Thornyheads are adapted to extreme deep-sea environments, enduring high pressures and low temperatures.
Longevityamazing
These fish are known for their remarkable longevity, with individuals recorded living over 100 years, making them one of the longest-lived fish species.
Commercial Importanceinteresting
Despite their deep-water habitat, Shortspine Thornyheads are a significant component of commercial fisheries in the North Pacific, often targeted by trawl fisheries.
Venomous Spinesbehavior
Like many members of the scorpionfish family, Shortspine Thornyheads possess venomous spines that can inflict painful wounds.
Slow Growthbehavior
Their deep-sea existence contributes to a very slow growth rate and late maturity, making them vulnerable to overfishing.
Safety Information
Handle with care- Safety level: caution
- Venomous: Yes
- Edibility: edible
- Handling notes: The Shortspine Thornyhead possesses venomous spines on its dorsal, anal, and pelvic fins. Punctures from these spines can cause significant pain, swelling, and discomfort. Handle with extreme caution, using thick gloves and appropriate tools to avoid direct contact with the spines. If stung, seek medical attention, and apply heat to the affected area (hot water immersion) to help denature the protein-based venom.
Similar Species
Longspine Thornyhead
Sebastolobus altivelis
The Longspine Thornyhead has significantly longer and more numerous head spines, particularly the parietal and nuchal spines. Crucially, its third dorsal spine is longer than the longest soft ray, whereas in the Shortspine Thornyhead, the third dorsal spine is shorter than the longest soft ray. The second anal spine is also typically shorter than the third in S. altivelis, opposite to S. alascanus.
Roughspine Thornyhead
Sebastolobus macrochir
The Roughspine Thornyhead is found primarily in the western Pacific (Japan, Okhotsk Sea) and has a more robust body and rougher scales. Its head spines are generally more pronounced and numerous than S. alascanus, and it typically has fewer pectoral fin rays (18-20).
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Actinopterygii
- Order
- Scorpaeniformes
- Family
- Sebastidae
- Genus
- Sebastolobus
- Species
- alascanus
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