With so many fascinating subjects to discover on the world's coral reefs, divers sometimes ignore the more common residents during searches for the rare and exotic. This is unfortunate because every fish has a fascinating story to tell those who take the time to stop and watch.
A good example of an easily-overlooked but fascinating marine subject is the dartfish. These small fish can be found in tropical waters around the world, from the Indo-Pacific and Red Sea to the Caribbean and Florida waters.
There are many different common names for dartfish, including dart gobies, gudgeons, hovering gobies and gudgeon-gobies — and each individual species might have up to a half-dozen common names. Adding to the confusion is an ongoing disagreement in the marine biology community regarding the specific classification of various dartfish species. Currently there are thought to be 21 members in the family, but that changes as new varieties are discovered, while others are combined and reclassified. What these fish have in common is a slender torpedo-like body, large eyes, a blunt head and a pronounced lower jaw.
Another thing all dartfish have in common is a shy and wary nature. To catch a dartfish in action, you'll need to swim up slowly and not get too close. When startled, these fish are quick to retreat into an underground lair or seek shelter in a nearby crevice in the reef. This darting behavior is what earned these fish their common name.
Dartfish are not difficult to locate. Find a sandy area or rubble patch on the reef that's exposed to passing currents. Dartfish prefer areas where there is water movement, because that's what delivers dinner their way. These fish feed on small zooplankton, but rather than waste time and energy foraging for a meal, they hold position in the flow and let the prey come to them.
Some species of dartfish are found singly or as part of a mated pair, while other types form small groups. When feeding, they usually hold position a few feet above the sea floor facing into the current. Dartfish have excellent eyesight and are quick to spot small morsels drifting their way. When a chosen target drifts within range, the dartfish opens wide and gulps down the snack.
The dartfish's hold-in-place feeding strategy techniques allow it to remain close to the safety of an underground sanctuary. Some species will dig their own burrows, using their tails to excavate the sand. Other species take advantage of holes already dug by crabs, shrimp or other species of fish. A relatively rare but fascinating strategy employed by some species is to move in with a shrimp-and-goby pair. The mutually beneficial relationship of gobies and shrimp is another fascinating story that you can read about on our blog. https://www.caradonna.com/blog/meet-oceans-original-odd-couple Essentially, the goby becomes the lookout for the near-blind shrimp, which in exchange does all the digging to maintain the shared burrow. When a dartfish joins the team, they provide an extra set of keen eyes, and will hover above the borrow to keep watch while their roommates guard the entrance.
Thanks to their shy and skittish nature, the home life and sex life of dartfish isn't well known. The males and females display the same shape and color, and the only time you could tell the difference is when a female swells up with eggs just before a spawn. The mating takes place underground and out of sight, and the fertilized eggs remain hidden until they hatch and a released into the currents to drift and forage in the flow. When the youngsters grow to about a half an inch in size they will settle onto the sand and start homesteading.
Though found worldwide, dartfish are most common in Indo-Pacific waters, and that's also where you will find many of the most colorful species, including the flame dartfish (aka firefish) the magnificent dartfish, the decorated dartfish and the pearly dartfish, named for it's lustrous, semi-transparent skin tone. But Caribbean divers can also join the hunt. The hovering dartfish can be found across the region, from the Bay Islands, Cozumel and the Cayman Islands to the Bahamas, while the bluestripe dartfish makes its home near southern islands such as Bonaire and Curacao. Florida divers are sometimes treated to sightings of blue dartfish at shallow and inshore sights such as Palm Beach's Blue Heron Bridge.
Dartfish are just one example of the many fascinating finds that await divers who take the time to slow down and observe details of life on a coral reef. So while the big fish and big walls may be the main attraction, don't forget to seek out the smaller treasures of a dive site.