Expedition Log: Palau – Day 16

For the past few weeks I have descended into Palau’s waters each day with my two vital pieces of equipment: a tape measure reel and writing slate. My job on this mission is to count, identify and measure reef fish throughout Palau’s reefs. Before this trip I never really had much appreciation for the very small reef fish, unlike my fellow fish surveyor Stefan. Instead I am drawn to the larger and more charismatic members of the reef. That was until I started counting dartfishes.

Zebra Dartfish (Ptereleotris zebra)
(Click-thru on image for greater detail.)

Dartfishes are small, elegant elongate reef fish from the family Microdesmidae and subfamily Ptereleotrinae. There are 20 species worldwide, and Palau contains 11 of these. So far, the fish team has managed to spot and ID six species—Fire Dartfish (Nemateleotris magnifica), Twotone Dartfish (Ptereleotris evides), Spottail Dartfish (Ptereleotris heteroptera), Monofin Dartfish (Ptereleotris monoptera) and Zebra Dartfish (Ptereleotris zebra)—and we seem to find at least one of these species during each dive in Palau. I’ve learned that the best place to spy these enigmatic little fish is hovering individually, in pairs or in small groups just above the seabed. As the dartfish hover they feed on tiny zooplankton from the water column. Most species are known to occur in relatively shallow waters, although one South African species, Ptereleotris lineopinnis, is found only in depths greater than 90m!

Fire Dartfish (Nemateleotris magnifica)
(Click-thru on image for greater detail.)

I have also learned that these beautiful fish are aptly named. As soon as I get too close with my tape measure or camera, they dart straight into their sandy burrow or under a rock. Unfortunately for them, they are very photogenic and appealing and the fish team are very persistent; so we have managed to snap a few photos!

 
Twotone Dartfish (Ptereleotris evides)
(Click-thru on image for greater detail.)

Photos by Ken Marks.