Har du et billede? Identificer fisk øjeblikkeligt med Fishby-appen.
Åbn appenBeskrivelse
Alosa fallax, commonly known as the Twaite Shad, is an anadromous clupeid fish, meaning it spends most of its life in saltwater but migrates to freshwater to spawn. It is a schooling fish, characterized by its silvery body, large scales, and a series of distinctive dark spots along its flanks. Twaite Shad are highly migratory and play an important ecological role as a prey species and as a link between marine and freshwater ecosystems. They are known for their energetic spawning runs and their sensitivity to habitat degradation and barriers to migration.
Fysiske karakteristika
- Kropsform
- compressed
- Farvetegning
- Silvery flanks, darker blue-green to greyish back, and a white belly. Often exhibits a series of 1 to 10 (typically 3-7) distinct dark spots along the upper flank, posterior to the operculum. The first spot is usually the most prominent.
- Skæltype
- cycloid
- Mundens placering
- terminal
- Kendetegn
- Large, deciduous cycloid scales, Deeply forked caudal fin, A series of dark spots along the flank (typically 3-7, but can be up to 10), Absence of teeth on the vomer, Relatively large eye, Strongly keeled belly with scutes
- Rygfinne
- Single, short-based dorsal fin located mid-body, typically with 16-19 soft rays.
- Halefinne
- Deeply forked caudal fin, symmetrical lobes.
- Brystfinne
- Relatively small, low-set pectoral fins, typically with 13-16 soft rays.
- Karakteristiske finner
- Pelvic fins are abdominal, small, and located beneath the dorsal fin origin. Anal fin is relatively long, with 19-23 soft rays.
Identifikationstips
Spots on Flank
Count the number of distinct dark spots along the upper flank, posterior to the operculum. Twaite Shad typically have 3-7 spots, whereas the closely related Allis Shad (Alosa alosa) usually has only one, or occasionally two or three, which are often less distinct.
Gill Rakers
Examine the gill rakers on the first gill arch. Twaite Shad have fewer (typically 40-60) and shorter gill rakers compared to Allis Shad (typically 90-130), which are longer and more numerous, adapted for filter feeding on smaller plankton.
Mouth and Teeth
Twaite Shad have a more pointed snout and a slightly more terminal mouth. While both species lack vomerine teeth, the overall mouth structure can be subtly different.
Size
Twaite Shad generally reach a maximum length of about 50-60 cm (20-24 inches) and a weight of 1-2 kg (2-4 lbs), while Allis Shad can grow slightly larger, up to 70 cm (28 inches).
Habitat
- Vandtype
- brackish
- Dybde
- Primarily pelagic in marine environments, typically found in coastal waters and estuaries. During spawning, they ascend rivers to freshwater sections, often in depths of 1-5 meters.
- Miljø
- Coastal marine waters, estuaries, and lower to middle reaches of large rivers for spawning. Prefers clear, well-oxygenated waters with gravel or sandy substrates for spawning.
- Geografisk udbredelse
- Eastern Atlantic Ocean, from southern Norway and the Baltic Sea south to Morocco, including the Mediterranean Sea. Also found in the Black Sea. Spawning rivers include those in the UK, Ireland, France, Spain, Portugal, Germany, and other European countries.
Akvarieoplysninger
- Plejeniveau: expert
- Temperament: peaceful
- Kost: carnivore
- Minimum akvariestørrelse: Not suitable for home aquaria due to their large size, migratory nature, and schooling requirements. Requires specialized public aquarium facilities.
- Temperatur: 10-20°C (50-68°F) in freshwater during spawning; wider range in marine environment
- pH-niveau: 7.0-8.0 (freshwater); 7.8-8.4 (saltwater)
- Hårdhed: Moderate to hard (freshwater); high (saltwater)
- Kompatibilitet: Not applicable for typical aquarium settings. In specialized large exhibits, compatible with other large, peaceful, migratory fish.
- Særlige krav: Requires vast, open water spaces, strong currents, and the ability to transition between freshwater and saltwater. Extremely challenging to maintain in captivity outside of dedicated research or public aquarium facilities.
Information om vilde bestande
- Bevaringsstatus: least concern
- Sæson: Spawning runs occur from late spring to early summer (typically April to July), depending on geographic location and water temperature. They are present in coastal marine waters for the rest of the year.
- Markedspris: Historically fished, but commercial fishing is now largely restricted or prohibited due to conservation concerns. Market price would be high if available, but rarely is.
- Kommerciel betydning: low
- Smag: Rich, oily, and flavorful, often compared to herring or mackerel.
- Konsistens: Flaky, tender, but very bony.
- Tilberedningsmetoder: Grilling, Baking, Smoking, Frying (often scored to mitigate bones)
- Næringsværdi: High in Omega-3 fatty acids, protein, and various vitamins and minerals.
Nøglefakta
Anadromous Migratorsbehavior
Twaite Shad are anadromous, meaning they live in saltwater and migrate to freshwater rivers to spawn. This makes them a crucial link between marine and freshwater ecosystems.
Multiple Spawnersbehavior
Unlike their close relative, the Allis Shad (Alosa alosa), Twaite Shad are iteroparous, meaning they can survive spawning and return to the sea to spawn again in subsequent years. Allis Shad are semelparous, typically dying after their first spawning event.
Nocturnal Spawningbehavior
Twaite Shad typically spawn at night, often in shallow, turbulent areas of rivers, producing characteristic splashing sounds that can be heard from the riverbanks.
Indicator Speciesinteresting
Due to their migratory nature and sensitivity to water quality and physical barriers, Twaite Shad are often considered an indicator species for the health of river systems and their connectivity to the marine environment.
Conservation Effortsinteresting
Conservation efforts for Twaite Shad often focus on removing or modifying barriers to migration (e.g., weirs, dams) and improving water quality in their spawning rivers.
Sikkerhedsoplysninger
Sikker- Sikkerhedsniveau: safe
- Giftig: Nej
- Spiselighed: edible
- Håndteringsnoter: No specific handling precautions are required beyond standard fish handling practices. Their scales are large and deciduous, so they can be easily dislodged if handled roughly. They are not venomous and do not possess sharp spines that pose a significant threat.
Lignende arter
Allis Shad
Alosa alosa
Allis Shad typically have only one dark spot (rarely 2-3) behind the operculum, and possess significantly more (90-130) and longer gill rakers on the first gill arch compared to Twaite Shad (40-60 gill rakers). Allis Shad also tend to spawn in deeper, faster-flowing river sections.
Atlantic Herring
Clupea harengus
Atlantic Herring are generally smaller, lack the distinct dark spots on the flank, and have a more streamlined body shape. Their scales are also smaller and less deciduous. Herring are exclusively marine.
Sardine/Pilchard
Sardina pilchardus
Sardines are much smaller, lack the distinct spots, and have a more slender body. They are exclusively marine and typically found in warmer waters.
Videnskabelig klassifikation
- Rige
- Animalia
- Række
- Chordata
- Klasse
- Actinopterygii
- Orden
- Clupeiformes
- Familie
- Clupeidae
- Slægt
- Alosa
- Art
- Alosa fallax
Udforsk Twaite Shad
Identificer fisk overalt
Gratis på iOS, Android og web. Fotoidentifikation, fulde artsoplysninger og meget mere.