The Spot Tail Dartfish, Ptereleotris heteroptera, is also known as the Blacktail Dartfish, Indigo Dartfish, Blue Gudgeon Dartfish and Blacktail Goby. They are relatively shy fish and as their name suggests are quick to dart into their burrows.
The Spot Tail Dartfish has a tubular shaped body which tapers backwards. Their dorsal fin is set far back and the anal fin extends forwards quite far. The body is a sky blue color and there is a bright blue iridescent line behind the eye and around the eye. In Tanzanian specimens the caudal fin is often transparent with a spot in the middle of the fin whereas in other areas the caudal fin is yellow.
SPOT TAIL DARTFISH IN THE WILD
Spot Tail Dartfish are usually seen hovering a meter or so above rubble or sandy areas of the reef. They are mainly seen in pairs but occasionally they may be seen in a small group of pairs. Normally they hover a meter or so above the substrate and dart upwards to feed on passing planktonic matter. Juveniles are seen in very large groups on shallow protected reefs in summer. Once the fish reach three to four centimeters in length these groups break up. They are very shy and are difficult to photograph well.
The Spot Tail Dartfish is found across the Indian ocean and in the west Pacific. They are found between depths of 8-50 meters. More usually they are seen around 15 to 18 meters in depth. They prefer rubble and sand to the reef.
The Spot Tail Dartfish feed on zooplankton and as a result are mainly found in areas with a fair amount of current. They hover above their burrow facing into the current and wait for zooplankton to come to them. They make quick darting movements to grab passing titbits.
Monogamous pairs are formed but very little seems known of their breeding habits. Some accounts have them keeping the eggs in the burrow tended by the males and others have them close to the burrow tended by both male and female.
SPOT TAIL DARTFISH CLASSIFICATION
- The Reef Guide fishes, corals, nudibranchs & other invertebrates: East and South Coasts of Southern Africa by Dennis King & Valda Fraser