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The Striped Killifish (Fundulus majalis) is a euryhaline, estuarine fish belonging to the family Fundulidae. It is characterized by its robust, somewhat compressed body and distinctive sexual dimorphism in coloration and patterning. This species is highly adaptable to a wide range of salinities and temperatures, making it a common inhabitant of coastal waters along the Atlantic and Gulf coasts of North America. It plays a significant ecological role as both a predator of small invertebrates and a prey item for larger fish and birds.
Physical Characteristics
- Body shape
- elongated
- Coloration
- Males typically exhibit 15-20 dark, vertical bars on their sides, often with iridescent blue or green hues, especially during breeding season. Females have 10-12 dark, horizontal stripes or rows of spots along their sides. Both sexes have a pale belly. Coloration can vary with habitat and mood.
- Scale type
- cycloid
- Mouth position
- terminal
- Distinctive features
- Sexual dimorphism in striping pattern (vertical bars in males, horizontal stripes/spots in females), Relatively large, flattened head, Terminal mouth with small, conical teeth, Robust body
- Dorsal fin
- Single dorsal fin, located posteriorly, with 10-13 soft rays. Origin is typically posterior to the anal fin origin.
- Tail fin
- Rounded to slightly emarginate caudal fin.
- Pectoral fin
- Moderately sized pectoral fins.
- Distinctive fins
- Anal fin with 10-12 soft rays, similar in shape to the dorsal fin. Pelvic fins are small and abdominal.
Identification Tips
Body Pattern (Males)
Look for prominent dark, vertical bars (15-20) on the sides, especially noticeable during breeding season when colors are more vibrant.
Body Pattern (Females)
Observe 10-12 dark, horizontal stripes or rows of spots along the sides, which is a key differentiator from males.
Head Shape
Note the relatively large and somewhat flattened head, characteristic of the genus Fundulus.
Mouth Position
The mouth is terminal (at the very front of the head), indicating its surface-feeding habits.
Habitat
Presence in shallow, brackish to marine estuarine environments is a strong indicator.
Habitat
- Water type
- brackish
- Depth
- Typically found in shallow waters, from intertidal zones to depths of a few meters.
- Environment
- Estuaries, salt marshes, tidal creeks, shallow coastal bays, and protected shorelines. Prefers areas with sandy or muddy bottoms, often associated with seagrass beds or other submerged vegetation. Highly tolerant of fluctuating salinities, from nearly freshwater to full marine conditions.
- Geographic range
- Atlantic and Gulf coasts of North America, from New Hampshire south to northeastern Florida, and along the Gulf Coast to northeastern Mexico (Tamaulipas).
Aquarium Information
- Care level: beginner
- Temperament: peaceful
- Diet: omnivore
- Minimum tank size: 20 gallons
- Temperature: 18-28°C (65-82°F)
- pH level: 7.0-8.5
- Hardness: 10-30 dGH
- Compatibility: Generally compatible with other peaceful, similarly sized brackish or marine species. Avoid highly aggressive or very small, delicate tankmates.
- Special requirements: Requires brackish to marine conditions. A well-filtered tank with plenty of hiding spots (rocks, plants, PVC pipes) and a sandy substrate is ideal. Can tolerate a wide range of salinities, but stable conditions are preferred. Live or frozen foods are readily accepted.
Wild Information
- Conservation status: least concern
- Seasonality: Active year-round in its range, with increased reproductive activity during warmer months (spring to late summer).
- Market price: N/A
- Commercial importance: low
- Taste: Not typically consumed by humans due to small size and bony nature.
- Texture: N/A
- Nutritional value: N/A
Key Facts
Sexual Dimorphismbehavior
Striped Killifish exhibit striking sexual dimorphism, with males having vertical bars and females having horizontal stripes, a rare trait among killifish.
Euryhaline Adaptabilityamazing
This species is remarkably euryhaline, capable of thriving in salinities ranging from nearly freshwater to hypersaline conditions, showcasing exceptional physiological adaptability.
Ecological Indicatorinteresting
Due to their abundance and tolerance to environmental fluctuations, Striped Killifish are often used as bioindicators in estuarine health studies.
Surface Feederbehavior
Their superior mouth position and feeding behavior indicate a preference for feeding on the water surface or in the water column.
Safety Information
Safe- Safety level: safe
- Venomous: No
- Edibility: not recommended
- Handling notes: Striped Killifish are harmless to humans. They can be handled safely with wet hands to minimize damage to their protective slime coat. No sharp spines or venomous glands. They are quite active and can jump, so care should be taken when handling or transferring them.
Similar Species
Mummichog
Fundulus heteroclitus
Mummichogs generally have a more robust body and less distinct patterning. Males typically have irregular vertical bars or blotches, not the clean, numerous vertical bars of male Striped Killifish. Females of F. heteroclitus lack the distinct horizontal stripes of female F. majalis. F. heteroclitus also has a more northern distribution, though their ranges overlap.
Spotfin Killifish
Fundulus luciae
Spotfin Killifish are much smaller (typically less than 5 cm) and have a distinct dark spot on the posterior part of the dorsal fin, which is absent in F. majalis. Their body shape is also more slender.
Marsh Killifish
Fundulus confluentus
Marsh Killifish are generally smaller and have a more slender body. Their coloration is typically more mottled or with irregular bars, lacking the distinct vertical bars of male F. majalis or the horizontal stripes of female F. majalis. Their range is primarily in the southeastern U.S.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Actinopterygii
- Order
- Cyprinodontiformes
- Family
- Fundulidae
- Genus
- Fundulus
- Species
- majalis
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