Slippery Dick Fish: What You Need to Know

The slippery dick is a tiny fish that does not grow beyond 35 cm. Interestingly, that’s not the only thing that makes it unique because this fish undergoes a sex change during its life cycle. If this intrigues you, keep reading to discover more interesting facts about this tiny, cigar-shaped fish.  

Photo of a slippery dick fish
Source: Wikimedia

Fish Profile: Slippery Dick

Scientific nameHalichoeres bivittatus
Other namesDoncella rayada
FamilyLabridae (Wrasses)
AppearanceJuveniles are white with a black lateral stripe. Initial phase slippery dick are grayish-white with a pinkish-red lateral stripe. Slippery dicks in the terminal stage are green with darker streaks.
DietCrabs, small fishes, sea urchins, shrimp, snails, polychaetes
Ave. weight and length12 cm (0.4 ft) to 35 cm (1.15 ft), 146 g (0.321875 lbs) maximum
HabitatRocky, coral reefs, and some seagrass beds, especially in the Epipelagic or sunlight zone
Spawning seasonMay and June
Depth range1 to 15m
Conversation statusLeast concern

What Is a Slippery Dick Fish?

The slippery dick fish, scientifically known as Halichoeres bivittatus, is a species of wrasse in the Labridae family. If you’re wondering how this fish got its name, well, its unique name is from the slippery mucus it secretes to fend off predators.

Fun Fact: Many anglers struggle to catch this fish even when using nets because of its slippery surface.  

You can find it in shallow, tropical waters, especially in Mexico. In addition, the fish has three stages; juvenile, initial, and terminal.

If you’re in Mexico, you know the thin, slippery dick by its common Spanish name, doncella rayada. 

What Does A Slippery Dick Look Like?

Slippery dick fish color and patterns depend on its life stage. If you expected a straight answer, you’re in for a surprise.

In the juvenile phase, they are white with a lateral stripe from the snout to the tail. You will also notice a greenish-yellow spot just above its pectoral fin. However, in the initial stage, they will have a whitish-gray, with a pink or red lateral line. They also have another stripe, parallel to the first, running through the gills.

During their terminal phase, slippery dicks are green, and the lateral stripe is darker than the two previous phases. These stripes are not necessarily straight. They can be broken, too, so don’t wonder if you see a beaded look. Also, the fish is easy to identify thanks to its cigar shape. 

Fun Fact: During the three stages, one physical appearance is retained, and that is the stripes that run from the fish’s tail fin or the caudal base to the eyes. 

Adding to the fish’s uniqueness are its three anal spines, 12 anal soft rays, and nine dorsal spines. 

Where Is Slippery Dick Caught?

You’ll find this fish roaming around rocky coral reefs across the subtropical waters of the western Atlantic Ocean, covering areas in the Gulf of Mexico, North Carolina, Bermuda, the Caribbean, and the Bahamas. 

If you plan on catching the slippery dick fish, aim for depths between 1-15m (49.2 ft). Also, this fish is quite common, so you won’t struggle to find it in all the Mexican waters. Besides, the IUCN lists its population as Least Concern. 

Tip: Slippery dick fish is not a food fish. Instead, you catch it for your aquarium. 

What Do They Eat? 

This fish species is a fan of benthic invertebrates. These are backbone-less organisms found at the bottom of the ocean. However, the slippery dick diet is diverse since you can keep it in an aquarium.

The following are common in the slippery dick’s diet:

  • Snails
  • Shrimps
  • Crabs
  • Sea cucumbers
  • Ophiuroids
  • Polychaetes (bristle worms) 
  • Sea urchins 

This fish species’ mouth, thick lips, and protruding teeth make grazing at the bottom much easier. In addition, the throat has toothed grinding plates.

Fun Fact: The slippery dick fish has enlarged canines and pharyngeal jaws to break down thick and hard crab shells.   

How Do They Reproduce? 

As mentioned earlier, slippery dick fish are protogynous hermaphrodites. They are females as they hatch, but some develop into males later in life for reproduction or mating. 

It takes about 3-4 weeks for sex reversal to complete. So, when the spawning season comes between May and June, terminals come together (in leks) to compete and attract females. For this reason, large adult males have unique and brighter color patterns to stand out. 

The terminal male that attracts a female the fastest swims to the top of the reef with the new partner. Since they are open pelagic spawners, they simultaneously release their gametes in the water in daylight. 

Then, fertilization occurs in the waters, where the fertilized eggs remain until they hatch (23 hours after fertilization). In some cases, males in their initial phase disrupt spawning, just as the fish are about to release gametes. Experts call this phenomenon streaking.  

Note: Slippery dicks don’t care for their young ones. Besides, the currents can carry eggs far from the fertilization site and the parent fish. 


You now know where to find the slippery dick fish and what it feeds on. Don’t let the protogynous hermaphroditism scare you.

This fish species changes from female to male to keep growing its population. Therefore, don’t worry about the color and pattern change. It’s all part of the reproductive dance!