More of our class explores Lighthouse Cave, San Salvador, Bahamas.
The angelfish is a very important reef fish in many tropical ecosystems, especially in the Indo Pacific and the Southwestern Atlantic. An article from The Conscientious Marine Aquarist states that their natural range is from “both sides of the Atlantic to the west mainly between the Bahamas, Florida to Southeastern Brazil. Occasionally, currents carry specimens farther up the eastern seaboard.” These fish have disc shaped bodies, small mouths, comb-like teeth, and vibrant colors; they are of close relation to the butterflyfish. Many characteristics, like coloration, of angelfish change between their juvenile and adult life spans. These fish are often disease resistant; they live long, and are known to make good aquarium fish. When the dominant male in the habitat leaves a female often undergoes a sex change and takes over the dominant male role. Also, some species are known to be mates for life. The angelfish is active at day and sheltered at night. They are sometimes known as coral fish and are recognized by their amazing colors.
Historically the angelfish belong to the family chaetodontidae along with the butterflyfish. This name means “bristle tooth” or “hair tooth” in Greek. However recently they have been put into a family of their own, the Pomacanthidae family. In this family there are 20 genera known and about 190 species known. Angelfish alone takes up about 8o species, in the Bahamas there are known to be between 7 and 11 species. A majority of the species lives in the Indo-Pacific. The angelfish have been divided into three different groups Holacanthus, Pomacanthus, and Centropyge. There are several species that exist within the Bahamian waters. Of the Holacanthus there is the tricolor, ciliaris, and bermudensis; the Pomacanthus includes the paru and the arcuatus these five are the larger of the angelfish that exist. Some species exist all over while others are specific to only one small island like the pygmy angelfish around Ascension Island.
The main difference between the angelfish and the butterflyfish is that the angelfish have a strong preopercular spine, and butterflyfish do not. Some scientists who have studied the nerves in the angelfish and the butterflyfish believe that they should belong to different families. Some sources do separate them into different families; the butterflyfish remain in the Chaetodontidae family while the angelfish are moved to the Pomacanthidae family. However, both have densely scaled vertical fins that are not divided, and their bodies look like discs that are thin and deep. These laterally thin bodies allow them slide into thin spaces and gaps at night. Their size ranges from a few centimeters to 24 inches.
Their coloring is very important because as they go from juveniles to adults colors change. The adult Bahamian species Holacanthus have brilliant colors (blues and yellows) while the Pomacanthus have brilliant marks. The Pomacanthus juveniles have bands of black and yellow or dark blue and white that form concentric rings, while the Holacanthus have vertical blue stripes that disappear as they grow older. There typically is no difference in the color of the female verses the male, however in one west pacific case, the genicanthus, the males are more strongly stripped and the females appear plain.
Most of their time they spend are in shallow reefs that are only above 30 m. They are extremely tolerant fish. They can generally withstand different ranges of temperature or salinity. The French angelfish are “euryhaline” which means not sensitive to a wide range of salinity. Some angelfish are herbivores while others are omnivores; adult angelfish tend to vary in the types of foods that they eat. This food can range from sponges, seaweed, coral polyps, plankton, algae, worms, small active invertebrates, and small crustaceans. They mainly eat encrusting plants and animals, but the size of the species determines their diet. The larger species tend to eat the shrimp, shellfish and worms, while the smaller ones eat the plankton. Some studies show that they are grazers. (Perez) The digestive tracts of both the Pomacanthus and the Holacanthus are similar. They have a small mouth with teeth, a short esophagus, and a stomach with thin walls connecting to long intestines.
Angelfish in the Bahamas are easy targets for spearing, and as a result their numbers decrease. They are easy targets because they can act curious and virtually fearless. When other fish attack them they can dive and take cover in the coral. However, the predators will quickly learn that they are bony and offer a poor meal. In addition with their dorsal spines up it would be very difficult to ingest. Some scientists believe that their bright colors do not attract other fish but that the colors are a warning sign that they are not good prey. When some angelfish are disturbed they make a drumming sound that startles their predators. The queen angelfish is quite large and her sound can be loud. Some sources, specifically those that are directed towards aquarium fish, state that the angelfish is quite disease resistant.
Humans are also a threat to fish on reefs. More than 95% of fish caught come from the continental shelf, this is the shallow region that many fish are in. This region is close to the shore and fishing boats depend upon it for their harvest instead of going farther out into the ocean where the water conditions are rougher. In addition to over fishing, humans cause pollution that threatens the species directly or the habitat that they thrive in. (Roberts) There have been attempts at protecting the fish through the establishment of marine reserves, however, their effectiveness does not show until long periods of time have passed. (Gerber) Another threat is the desire for juvenile angelfish as aquarium fish. They sometimes sell for up to $100 American each. The threat is unknown, but it is suspected because the juveniles have not yet reached a breeding age. (Perez)
According to studies of adult angelfish they can live in pairs sometimes for life, unlike their juveniles who swim solo when they are at their cleaning stations. When they are in pairs, like the butterflyfish more commonly do, they swim synchronized facing the same direction at all times. Many angelfish are territorial, however the juveniles of both sexes are more territorial than adults. At night the fish slide into holes and gaps in the coral or hide behind corals before becoming inactive, but during the day they come out. A group of angelfish may include 4 females and one dominant male. If the male is displaced from the group a female will change sex over the course of only a few weeks. Yoichi Sakai, author of Rapid transition in sexual behaviors during protogynous sex change in the haremic angelfish Centropyge vroliki (Pomacanthidae), observed that the most dominant female will take over the role on the first day and change her sex to begin spawning over days 1 through 3. Sex change has been studied and found in over 24 species of the angelfish. (Sakai) This fish will defend the others and take on the task of fertilizing all of the eggs. First, the females lay the eggs and then the male fertilizes them, next they are left to float out to sea; many do not survive.
Juvenile angelfish, specifically the Pomacanthus paru, spend their days cleaning client fish. This is "a cooperative, interspecific interaction among reef fishes. During cleaning interaction cleaner fish seek food on the body surface of other fishes which, in turn, are rid of parasites and debris, and receive tactile stimulation." (Sazima) At the station the angelfish performs a fluttering swimming and touches the other fish with its pelvic fins. There are many types of clients that the angelfish clean, including predators like the grouper, jacks, and morays. The cleaning has been observed mainly in sea grass and flats. (Sazima) The cleaner fish mostly clean the flanks and fins, but in some cases they cleaned the heads (queen triggerfish and the white grunt).
The angelfish is a very extraordinary fish. Although it shares many characteristics with other fish, it has many interesting habits. The angelfish undergoes many changes throughout its lifetime. It starts as a juvenile with brilliant concentric circles as a pattern over its body and as it grows older it changes to a solid gray with blue and yellow highlights, still standing out in the ocean waters to divers who are privileged to encounter such a fish. Another important change that larger females undertake is the sex change when the male leaves the group. Besides all of the changes these angelfish as juveniles graciously clean other fish and as adult they graciously synchronize swim with their partners. As humans, with the power and control that we take over the ocean’s edge we owe it to all the species to protect and learn from them, especially our ocean’s angels.
Gerber, Leah.., Kareiva, Peter., and Bascompte, Jordi. “The influence of life history attributes and fishing pressure on the efficacy of marine reserves.” Biological Conservation. 11 September 2001: 11-18.
Hughes, Terry., Bellwood, David., and Connolly, Sean. “Biodiversity hotspots, centres of endemicity, and the conservation of coral reefs.” Ecology Letters. 2002: 775- 784.
Morgan., Laplaza, Gomez. “The influence of social rank in the angelfish, Pterophyllum scalare, on locomotor and feeding activities in a novel environment.” School of Biosciences. Birmingham, UK. 2003: 108-120.
Perez-Espana, H., and Cardenas, Abitia. “Description of the digestive tract and feeding habits of the king angelfish and the Cortes angelfish.” Journal of Fish Biology. 12 June 1995: 807-817.
Perez-Espana, H., and Diaz, Martinez. “Feasible mechanisms for algal digestion in the king angelfish.” Journal of Fish Biology. 4 June 1999: 692-703.
Roberts, Callum., and Hawkins, Julie. “Extinction risk in the sea.” Environmental Dept., University of York. York, UK.
Sakai, Yoichi., Tsujimura Chihiro., Yukari Nakata., Tanabe, Hisayo., and Maejima, Go. “Rapid transition in sexual behaviors during protogynous sex change in the haremic angelfish Centropyge vroliki (Pomacanthidae).” Ichthyological Research Society of Japan. 6 September 2002: 30-35.
Sazima, Ivan., Moura, Rodrigo., and Sazima, Christina. “Cleaning activity of juvenile angelfish, Pomacanthus paru, on the reefs of the Abrolhos Archipelago, western South Atlantic.” Environmental Biology of Fishes. Published in the Netherlands, 1999: 399-407.
“The French Angelfish, Pomacanthus paru.” The Conscientious Marine Aquarist. Available: http://www.wetwebmedia.com/marine/fishes/angels/pomacanthus/paru.htm.
Angelfish Pictures: http://www.snap-shot.com/pages/fish/angel.html
“The angelfish.” (2002) PageWise Inc. Available: http://allsands.com/Pets/Fish/angelfish_aem_gn.htm
“Angelfish: Beauties of the Reef.” Green Reef, Belize. Available: http://www.greenreefbelize.com/reefbriefs/briefs83.html
“Angelfish.” (2002-2003) Enchanted Learning. Available: http://www.enchantedlearning.com/subjects/fish/printouts/Angelfishprintout.shtm
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