Biological Diversity 2003     

This image courtesy of: Wades Page

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Labridae
Species: bifasciatum


This image courtesy of


Wrasses in Motion!

Wrasse feeding around sponge

Several Wrasse swimming

(Video clips provided by Rock and Wreck)

Male blue-headed wrasse with harem.
This image courtesy of
Science News.

There's no place like home...

Komodo Reef picture
courtesy of The Nature Conservancy

Courtesy of Mother Jones Action Atlas


Coral Reef Destruction

Plastic bags and other debris can harm reefs, causing them to "suffocate".
Image from

Star coral starting to bleach
This image courtesy of E.C. Peters at
Ocean World

Red indicates areas in the world where
coral reefs are in danger.

Courtesy of Ocean World


Coral Conservation Organizations

Coral Reef Background
This site wil give you the skinny on coral reefs including their anatomy, the habitat requirements they have, and the many types of coral reefs found in the Carribean.

The Atlantic and Gulf Rapid Reef Assessment (AGRRA) Program is an international collaboration of scientists and mangers aimed at determining the regional condition of reefs in the Western Atlantic and Gulf of Mexico.

Coral Reef Alliance
The Coral Reef Alliance (CORAL) is a member-supported, non-profit organization dedicated to keeping coral reefs alive around the world.

Reef Relief
Reef Relief is a nonprofit organization dedicated to the preservation and protecion of coral reefs through local, regional and global efforts.

National Action Plan to Conserve Coral Reefs
In March 2000, the U.S. Coral Reef Task Force released the National Action Plan to Conserve Coral Reefs. The plan outlines the strategies for understanding, conserving and protecting the nation's coral reef ecosystems. The NOAA (National Oceanic and Atmospheric Administration) efforts thus far to fulfill the goals of the National Action Plan are described.

The Nature Conservancy
Their mission is to preserve the plants, animals, and natural communtities that represent the diversity of life on Earth by protecting the environments they need to survive in. They have protected more htan 98 million acres of lands and waters worldwide.

Wrasse Fun
Thought learning about Blue Headed Wrasse was all facts and statistics? WRONG!
Check out these fun Wrasse activities:
Color-by-number primary male
Color-by-number secondary male
Word Find


Blue Headed Wrasse

The Blue Headed Wrasse is one of the most prevalent fish on coral reefs. They are often found in schools of hundreds or even thousands, and besides their unique coloring, they are know for their unique reproductive strategies and adaptations in the science world.

You will find these colorful fish on coral reefs in Bermuda, the Bahamas, the Caribbean, the Gulf of Mexico, the northern South Amercian coast, and the Atlantic coast of Florida.

Food and Feeding
The diet of the Blue Headed Wrasse varies, but largely consists of copepods (small crustaceans), crabs, crab larvae, trematodes (flatworms), zooplankton, gastropods and gastropod larvae (Norton, Costello, 1996). Juvenile Blue Headed Wrasse often act as cleaner fish (Hood). They also eat plankton found on coral reef’s perimeters.

Physical Characteristics
A Blue Headed Wrasse population is composed of three different groups:
1.) the non-sex-changing primary males, who are small and plain.
2.) the females, who are yellow. Females and primary males are generally referred to as being in initial phase.
3.) the secondary (or terminal) males, who have blue heads and green bodies separated by two black stripes (these males were initially females who went through a sex change (Louch)).

One secondary male wrasse swimming with harem of females.
Courtesy of Georgia State University.

Blue Headed Wrasses are protogynous (female first) sequential hemaphrodites. This means that when the secondary male in a community dies, the largest female changes into a male.

Every afternoon, secondary males gather and wait for females to return from feeding (McIntyre). Terminal males are pair-spawning. They form “harems” and mate with only one female at a time. Secondary males experience huge breeding success. Estimates of breeding range from 25 times an afternoon (Deloach, 1995) to up to 40 times a day (Louch).

Primary males have little breeding success. Instead of mating one-on-one, they release sperm into the water. They must either covertly spawn with a female or travel in gangs, hoping to catch a female outside the sight of a secondary male. Often, they gather immediately outside the spawning sites of the secondary males, hoping to sneak access to females (Warner).

Accurate portrayal of removal of secondary male in a population...
The biggest female then changes into a male.

This image courtesy of McIntyre.

Once hatched, juvenile fish have to find protection. Coral reefs provide the perfect habitat for protection from predators, food, and reproductive practices.

Breeding vs. Habitat
The specifics of breeding are different on large reefs and on small reefs. The plethora of wrasses found on large reefs enables primary males to experience high breeding success. The secondary males are often distracted and not able to constantly monitor females. In extremely large reefs, where it becomes very hard for males to defend females, the proportion of primary males in a population can reach 50% and the
amount of secondary males can be as low as 19%.

On small and medium-sized reefs, there are fewer wrasses and primary males are very unlikely to have breeding success. Secondary males control all the favored breeding sites and monopolize mating (McIntyre). Consequently, the vast majority of wrasses are born female. However, Blue Headed Wrasses frequently experience socially controlled sex changes (Louch). When the secondary male dies or is removed, the largest wrasse (usually a female, but occasionally a primary male) begins changing color and within weeks, or even days, transforms completely into a secondary male (Deloach, 1995).

Coral Conservation Status
The Blue Headed Wrasse, although not an endangered species, are prime candidates for becoming endangered because of the destruction of their natural habitat...coral reefs. Blue Headed Wrasses are considered "'homebodies'". They rarely leave the reef from which they were spawned making the protection of their reef microenvironments crucial to maintaining the numerous subspecies of Wrasses found on specific coral islands (Clark, 2003).

This image courtesy of the
National Action Plant to Conserve Coral Reefs

Conservation Issues
Coral reefs are one of the greatest habitats for biodiversity on Earth. They are home to one quarter of all marine plants and animals: Nearly a million species of fish including the Blue Headed Wrasse, crabs, eels, mollusks, sponges, worms, grasses, algae, and other marine animals live on reefs or use them as places to protect their young (Reef Relief, 2001). Corals also naturally filter seawater for its neighbors. These reef ecosystems support vast fisheries that people, especially in coastal nations, depend upon for much of their protein. Barrier coral reefs can protect shorelines from erosion and storm damage (Reef Relief, 2001). This ecosystem benefits humans and numerous species. The protection of coral reefs is crucial for its many species to remain existent.

Many different abiotic, and biotic forms of disturbance that affect coral reefs include: coral bleaching, human harvesting, disease, other human activity, and many more.

Coral is unique in that it lives a symbiotic life with an organism called zooxanthellae (zoo-zan-thel-y). Inside the sac of each coral polyp lives the one-celled algae. The algae gives off oxygen and other nutrients that the coral polyp needs to live and in return the polyp gives the algae carbon dioxide and other substances the algae needs. The algae need sunshine for photosynthesis. That is why coral reefs grow so close to the surface of the water where it is the sunniest (Ocean World, 2003).

When sea temperatures rise or other stresses occur the corals expel their zooxanthellae. This is called coral bleaching. One environmental concern is global warming, as it contributes to increasing water temperatures that have been connected to coral bleaching (Hall and Hall 2003).

Another concern is human harvesting. Over fishing can destroy populations of fish that help keep reefs healthy (Hall and Hall 2003). Destructive fishing techniques and over-harvesting of fish and tropical marine life is known to be a worldwide problem (Reef Relief, 2001). Fishing can be a very positive factor in population management, but too much of anything can lead to problems.

Diseases such as, Rapid Waste Disease, Yellow Pox Disease, White and Black Band Disease, and infections such as Aspergillosis (Smith, 2003) can cause large mortality rates in small species habitats. These diseases can be caused by any number of different things, generally stemming from bacteria in the water.

One may not think that what occurs on land can affect the ecosystems within the ocean, but it does. Agricultural run-off that contains pesticides and fertilizers add toxins and nutrients to reefs that require nutrients-free waters to thrive. Over-development and lack of sewage and storm water infrastructure in coastal areas is also a leading source of damage to reefs. Humans also play are more direct role in the destruction of coral reefs. Divers and snorkelers touch and step on the reef, breaking it. Boat groundings and propellers damage corals and sea grasses, along with many other species (Reef Relief, 2001).

As humans we need to be more aware of our surroundings and what we can do to ensure their stability. So next time you’re snorkeling, DON’T STEP ON THE REEF!

Literature Cited
Costello, M.J. 1996. Development and future of cleaner-fish technology and other biological control techniques in fish farming. 171-184 in M.D.J.

Deloach, N. 1995. Reef fish behavior. Jacksonville: New World Publications.

Hall, Howard and Michele Hall. 2003. Sixty Fathoms Under the Sea. National Wildlife: World Addition 41(3):52-56.

Hood College. Date Unknown. Thalasoma bifasciatum.
Accessed 2003 April 3.

Louch, C. Date Unknown. Fish Tales. Accessed 2003 April 3.

McIntyre, K. Date Unknown. Sex change you say???
Accessed 2003 April 3.

Norton, S. Date Unknown.Bluehead wrasse. Fishes of North Carolina Rock and Wreck.
dWrasse.html Accessed 2003 April 3.

Oceanworld. 2003. Coral Reef Destruction and Conservation.
Accessed 2003 April 3.

Reef Relief. 2003. All About the Coral Reef Accessed 2003 April 3.

Sayer, editor. Wrasse: Biology and use in aquaculture. Oxford: Fishing News Books.

Smith, Garriet. 2003. The Decline of the Coral Reef- Coral Bleaching and Diseases with Dr. Garriet W. Smith Accessed 2003 April 3.

Global Warming: Early Warning Signs.1999. Accessed 2003 April 3.


Images Cited

Authors: Corliss Harris, Melissa Maheux, Emily Shepard
Creation/revision date: 31 March 2003

Aloe Vera Amanita phalloides American Lobster Attwater's Prairie Chicken Bacillus anthracis Basilisk Lizard Blue-headed Wrasse Blue-ringed Octopus Botflies Ethnobotany and A. araucana Hyacinth Macaw Indiana Bat Leafy Sea Dragon Leishmania Maned Sloth Platypus Rafflesia Ring-tailed Lemur Baiji Spanish Dancer St. Croix Ground Lizard Tomatoes Vampire Squid

This website is part of a Biology 226 class project on the conservation of global biodiversity.

Earlham · Biology Department · Biology 226: Biological Diversity

Copyright ©-2001 Earlham College. Revised 31 March 2003. Send corrections or comments to,,