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The Shortfin scad (Decapterus macrosoma) is a pelagic schooling fish belonging to the family Carangidae. It is characterized by its elongated, fusiform body, typical of fast-swimming pelagic species. This species is an important component of artisanal and commercial fisheries throughout its range, often forming large schools in coastal and offshore waters.
Physical Characteristics
- Body shape
- torpedo
- Coloration
- Dorsal side metallic blue to blue-green, fading to silvery white on the flanks and belly. A small, distinct black spot is present on the upper margin of the operculum. The caudal fin is typically yellowish.
- Scale type
- cycloid
- Mouth position
- terminal
- Distinctive features
- Elongated, slender body, Adipose eyelid well developed, covering most of eye except for a vertical slit over pupil, Lateral line with a long anterior arch and a straight posterior section, Scutes present along the straight part of the lateral line, numbering 24-40, A small, distinct black spot on the upper margin of the operculum, Two separate dorsal fins
- Dorsal fin
- Two dorsal fins; the first with 8 spines, the second with 1 spine and 28-33 soft rays, followed by a detached finlet of 1 spine and 1 ray.
- Tail fin
- Deeply forked caudal fin, typically yellowish.
- Pectoral fin
- Short pectoral fins, shorter than the head length, typically 1/3 to 1/2 of the head length.
- Distinctive fins
- Anal fin with 2 detached spines anteriorly, followed by 1 spine and 24-28 soft rays, and then a detached finlet of 1 spine and 1 ray. Pelvic fins are small.
Identification Tips
Body Shape
Look for the distinctly elongated and slender body, which is more streamlined than many other scad species.
Pectoral Fin Length
The pectoral fins are notably short, usually less than half the length of the head. This is a key distinguishing feature from other Decapterus species.
Opercular Spot
A small, but clear, black spot on the upper edge of the operculum (gill cover) is consistently present.
Finlets
Presence of a single detached finlet behind both the dorsal and anal fins.
Lateral Line Scutes
Count the scutes (hardened scales) along the straight posterior section of the lateral line; there are typically 24-40 in D. macrosoma.
Habitat
- Water type
- saltwater
- Depth
- Typically found in coastal and offshore waters from the surface down to about 100 meters (330 feet), though occasionally deeper.
- Environment
- Pelagic, schooling species found over continental shelves and slopes, often associated with reefs or seamounts. Prefers clear, warm tropical and subtropical waters.
- Geographic range
- Widespread in the Indo-Pacific region, from the Red Sea and East Africa eastward to the central Pacific, including Japan, Australia, and many Pacific island nations. Also found in parts of the eastern Pacific.
Aquarium Information
- Care level: expert
- Temperament: peaceful
- Diet: carnivore
- Minimum tank size: 500 gallons
- Temperature: 24-28°C (75-82°F)
- pH level: 8.1-8.4
- Hardness: 8-12 dKH
- Compatibility: Best kept in large, species-specific tanks or with other large, fast-swimming pelagic fish. Not suitable for typical home aquariums due to size and schooling needs.
- Special requirements: Requires very large tanks with strong filtration and ample swimming space. Prone to stress in confined environments. Mimicking natural schooling behavior is crucial for their well-being.
Wild Information
- Conservation status: least concern
- Seasonality: Available year-round in many parts of its range, with peak catches often coinciding with specific spawning or feeding aggregations.
- Market price: Varies significantly by region and season, generally moderate.
- Commercial importance: high
- Taste: Mild, slightly oily
- Texture: Firm, flaky
- Cooking methods: Grilling, Frying, Steaming, Baking, Smoking
- Nutritional value: Good source of protein, Omega-3 fatty acids, and various vitamins and minerals.
Key Facts
Schooling Behaviorbehavior
Shortfin scads are highly schooling fish, often forming large aggregations that can extend for considerable distances, especially during feeding or migration.
Fast Swimmersbehavior
Their torpedo-shaped body and deeply forked caudal fin are adaptations for fast, sustained swimming in open water.
Important Forage Fishinteresting
As a schooling pelagic species, Shortfin scads serve as a crucial food source for larger predatory fish, marine mammals, and seabirds, playing a vital role in marine food webs.
Nocturnal Feederbehavior
While they can feed during the day, Shortfin scads are often more active feeders at night, preying on zooplankton and small invertebrates.
Safety Information
Safe- Safety level: safe
- Venomous: No
- Edibility: edible
- Handling notes: No specific handling precautions are required beyond standard fish handling practices to avoid fin pricks. Not venomous or dangerous.
Similar Species
Round scad
Decapterus punctatus
D. punctatus has longer pectoral fins (usually longer than head length) and a more rounded body profile. The number of lateral line scutes also differs.
Redtail scad
Decapterus kurroides
D. kurroides has a reddish caudal fin and generally a more robust body. Its pectoral fins are also longer than those of D. macrosoma.
Indian scad
Decapterus russelli
D. russelli typically has a more compressed body and a different count of lateral line scutes (usually 30-40). Its pectoral fins are also longer.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Actinopterygii
- Order
- Carangiformes
- Family
- Carangidae
- Genus
- Decapterus
- Species
- macrosoma
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