How to Identify Forktail Rainbowfish

To identify Forktail Rainbowfish (Pseudomugil furcatus), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Males exhibit a vibrant yellow coloration on their dorsal, anal, and caudal fins, often with distinct black margins. The body is typically silvery-blue to olive-brown, with a darker stripe running laterally. Females are generally more subdued, with translucent to pale yellow fins and a less intense body coloration. Both sexes have prominent blue eyes.

Scale type

cycloid

Mouth position

superior

Distinctive features

Bright yellow fins with black edges (especially in males), Deeply forked caudal fin, Prominent blue eyes, Two dorsal fins, the first being small and spiny, the second larger and soft-rayed

Dorsal fin

Two dorsal fins; the first is small with 4-7 spines, the second is larger with 1 spine and 7-10 soft rays. In males, the second dorsal fin is often elongated and brightly colored.

Tail fin

Deeply forked caudal fin, often bright yellow with black margins in males.

Pectoral fin

Transparent to yellowish, relatively small.

Distinctive fins

The elongated and brightly colored second dorsal and anal fins of males are a key distinguishing feature, along with the deeply forked caudal fin.

Identification Tips

1. 1

   Fin Coloration

   Look for the bright yellow fins, especially the dorsal, anal, and caudal fins, often with distinct black edges. This is most pronounced in males.

2. 2

   Caudal Fin Shape

   The deeply forked caudal fin is a key identifier and the origin of its common name.

3. 3

   Eye Color

   The prominent blue eyes are characteristic of the Pseudomugil genus, including P. furcatus.

4. 4

   Body Size and Shape

   Small, slender body, typically reaching a maximum size of 4-5 cm (1.6-2 inches).

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