How to Identify Longfin eel

To identify Longfin eel (Anguilla dieffenbachii), look at these key features.

Physical Characteristics

Body shape

eel-like

Coloration

Adults are typically dark brown to black on the dorsal surface, fading to a lighter, often yellowish or greyish, ventral side. Juveniles (elvers) are transparent, becoming darker as they mature.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Dorsal fin originates significantly anterior to the anal fin (a key diagnostic feature)., Large, broad head with a prominent lower jaw., Thick, muscular body., Small, embedded scales, giving a smooth appearance., Large, well-developed pectoral fins.

Dorsal fin

Very long, confluent with the caudal and anal fins, originating well in front of the anal fin.

Tail fin

Rounded, confluent with dorsal and anal fins.

Pectoral fin

Relatively large and fan-shaped.

Distinctive fins

The position of the dorsal fin origin relative to the anal fin is the most distinctive feature.

Identification Tips

1. 1

   Dorsal Fin Origin

   The most reliable identification feature: the dorsal fin starts much closer to the head than the anal fin. If you can draw a vertical line from the anal fin origin, the dorsal fin will be well in front of it.

2. 2

   Head Shape

   Possesses a broad, somewhat flattened head with a prominent lower jaw, giving it a slightly 'bulldog' appearance compared to other eel species.

3. 3

   Size

   Adults are typically much larger and more robust than other New Zealand eel species, often exceeding 1 meter in length.

4. 4

   Coloration

   Generally darker, often black or dark brown dorsally, with a lighter belly, though coloration can vary with habitat.

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