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Retropinna semoni, commonly known as the Australian Smelt, is a small, slender, schooling freshwater fish native to southeastern Australia. It is characterized by its translucent body, silvery sides, and a distinctive cucumber-like odor when freshly caught. This species plays a significant ecological role as a forage fish in its native habitats.
Physical Characteristics
- Body shape
- elongated
- Coloration
- Translucent to pale olive-brown dorsally, silvery on the sides and belly. A distinct silvery lateral band is often present.
- Scale type
- cycloid
- Mouth position
- terminal
- Distinctive features
- Small adipose fin present between the dorsal and caudal fins., Distinctive cucumber-like odor when fresh., Large eyes relative to head size.
- Dorsal fin
- Single dorsal fin, typically with 9-12 soft rays, positioned well back on the body, posterior to the pelvic fins.
- Tail fin
- Forked caudal fin.
- Pectoral fin
- Small, low-set pectoral fins.
- Distinctive fins
- Presence of a small, fleshy adipose fin, characteristic of the family Retropinnidae.
Identification Tips
Adipose Fin
Look for the small, fleshy fin located between the dorsal fin and the caudal fin. This is a key characteristic of the family Retropinnidae.
Body Shape and Coloration
Slender, elongated body, translucent to pale olive-brown back, and silvery sides with a prominent lateral band.
Size
Typically small, rarely exceeding 10 cm in total length.
Odor
When freshly caught, it emits a distinct cucumber-like smell, which is a reliable field identification cue.
Habitat
- Water type
- freshwater
- Depth
- Typically found in shallow to moderate depths of rivers, streams, lakes, and impoundments.
- Environment
- Prefers clear, cool, well-oxygenated waters with moderate flow. Often associated with aquatic vegetation or submerged structures for cover. Can tolerate a range of substrates from sand to gravel and mud.
- Geographic range
- Southeastern Australia, including the Murray-Darling River system, coastal drainages of New South Wales, Victoria, and South Australia, and Tasmania.
Aquarium Information
- Care level: intermediate
- Temperament: peaceful
- Diet: carnivore
- Minimum tank size: 75 liters (20 gallons)
- Temperature: 10-25°C (50-77°F)
- pH level: 6.0-7.5
- Hardness: 5-15 dGH
- Compatibility: Compatible with other small, peaceful, cool-water fish. Avoid housing with aggressive or much larger species.
- Special requirements: Requires well-oxygenated water, a planted tank with open swimming areas, and a fine substrate. Sensitive to poor water quality. Best kept in schools of 6 or more individuals.
Wild Information
- Conservation status: least concern
- Seasonality: Spawning typically occurs in spring and early summer, but can vary with local conditions.
- Market price: Not typically sold commercially for consumption, occasionally available for aquariums.
- Commercial importance: low
- Taste: Mild, delicate, often described as having a cucumber-like flavor.
- Texture: Soft, flaky.
- Cooking methods: Fried, Pan-seared, Baked
- Nutritional value: Good source of protein and omega-3 fatty acids.
Key Facts
Cucumber Scentinteresting
The Australian Smelt is famously known for emitting a distinct cucumber-like odor when freshly caught, a characteristic shared with some other smelt species.
Ecological Rolebehavior
As a small, abundant schooling fish, Retropinna semoni serves as a crucial forage species, forming a significant part of the diet for larger predatory fish and birds in its ecosystem.
Adipose Fininteresting
The presence of a small, fleshy adipose fin (a fin without rays, located between the dorsal and caudal fins) is a key morphological feature that places it within the family Retropinnidae.
Schooling Behaviorbehavior
Australian Smelt are highly social fish, typically found in large schools, which provides protection against predators and aids in foraging efficiency.
Safety Information
Safe- Safety level: safe
- Venomous: No
- Edibility: edible
- Handling notes: No specific handling precautions are required. They are small, harmless fish. Handle gently if caught for release or observation to minimize stress.
Similar Species
Common Smelt
Retropinna retropinna
R. retropinna is a New Zealand species and is not found in Australia. Morphologically, R. semoni generally has a more slender body and a slightly different fin ray count, though precise identification often requires expert examination.
Tasmanian Smelt
Retropinna tasmanica
R. tasmanica is endemic to Tasmania and typically has a deeper body and a more pronounced silvery sheen compared to R. semoni. Genetic analysis is often required for definitive differentiation.
Australian Grayling
Prototroctes maraena
While also having an adipose fin and a similar body shape, the Australian Grayling is generally larger, has a more brownish-gold coloration, and a more pointed snout. Its mouth is also smaller and more inferior.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Actinopterygii
- Order
- Osmeriformes
- Family
- Retropinnidae
- Genus
- Retropinna
- Species
- Retropinna semoni
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