Diversity
Diversity of reef organisms

A healthy reef supports a rich diversity of organisms.  CLICK ON a "hot" button to see some examples of Caribbean reef plants and animals. Throughout the VIRTUAL DIVE we’ll see these and many other reef-dwellers and will study what they do, how they behave, and how they interact. 

hot buttons for diversity section of BIOLOGY OF CARIBBEAN CORAL REEFS website diversity of corals diversity of gorgonians diversity of sponges diversity of worms diversity of molluscs diversity of crustaceans diversity of echinoderms diversity of tunicates diversity of turtles diversity of fishes diversity of sharks/mammals
hot button for sharks/mammals-diversity section of BIOLOGY OF CARIBBEAN CORAL REEFS website

Sharks/rays/mammals

There are about a dozen species of sharks, half a dozen rays, and another half-dozen dolphins and whales in the Caribbean region. On a given SCUBA dive, depending on the area and depth, a diver might expect to see a dolphin or two from the dive boat and, underwater, perhaps a shark and, on sandy bottoms, a southern stingray. Like all world species, numbers of Caribbean sharks have been decimated through overfishing to levels perhaps only 10% of those in the 19th Century.

A recent assessment of stocks of southern stingrays Dasyatis americana in the shallow lagoon areas of Glovers Reef Atoll, Belize indicates a density of about 250 individuals per square kilometer, or 8400 in total in the entire atoll.  This high density bodes well for their continued survival, in sharp contrast to the decimated situation of sharks. Tilley & Strindberg 2013 Aquat Conserv: Mar & Freshw Ecosyst 23: 202.

NOTE  this species of elasmobranch is by far the most numerous in the lagoons.  Other related species noted by the authors include nurse sharks, eagle rays, and “uncounted observations” of yellow stingrays Urolophus jamaicensis

photograph of southern stingray Dasyatis americana photograph of yellow stingray Urolophus jamaicensis
Southern stingray Dayatis americana Yellow stingray Urolophus jamaicensis

seahorse dive leader in the BIOLOGY OF CARIBBEAN CORAL REEFS website photograph of a coral reef taken from a video

"Divers are always looking for the big stuff. Sharks, dolphins, and whales are usually transient, while rays, such as eagle rays and this southern stingray, may hang around for a time."
- Turneffe Island. Video courtesy Andy Stockbridge, Belize

NOTE the spotted eagle rayAetobatus narinari is hosting at least one remora on its back

NOTE Dasyatis americana


   
seahorse dive leader photograph of a nurse shark taken from a video Nurse sharks Ginglymostoma cirratum are nocturnally active, hunting for food items such as crustaceans, molluscs, fishes, and rays. During the day they are commonly found in shallow water, often resting on their fins. Although their mouths are relatively small, their thraats apparently have a kind of bellows-valve construction, enabling them to suck in prey. Unlike most open-water species that need to swim to create adequate ventilation, nurse sharks are able to pump water actively through their branchial chambers. Nurse sharks are not commercially fished to any great extent, and consequently their numbers remain relatively high - Turneffe Island, Belize. Video courtesy Andy Stockbridge, Belize

   
seahorse dive leader photograph of a silky shark taken from a video Silky sharks Carcharhinus falciformis are not often seen by SCUBA divers because they mostly inhabit oceanic waters. Named for the smoothness of their skin, the species is a fast, aggressive, and effective hunter of bony fishes, such as tuna, and cephalopods. In 2007 the International Union for Conservation of Nature raised its status from one of "little concern" to "near threatened" - Turneffe Island, Belize. Video courtesy Andy Stockbridge, Belize

   
seahorse dive leader photograph of reef shark taken from a video The reef shark Carcharhinus perezi is the species most commonly seen on SCUBA dives. This video was made at about 120ft depth in the Blue Hole, Belize. For some reason, presumably an ample food supply, the sharks hang out there at deep depths. Food generally consists of a variety of fish species, cephalopods, and sometimes rays. The reef shark is the most common participant at shark "feeding stations", and much money is invested by tourist divers at different locations in the Caribbean, most notably in the Bahamas. In this respect, Wickipedia lists the value of a single reef shark in tourist dollars at around $40,000, as compared with a fish-market value of perhaps $50-100. The practise is not without controversy, as it requires provision of bait fish and additionally is thought to decrease the normal "shyness" of the species, possibly leading to more attacks on humans (of which the reef shark is the overall Caribbean leader) - Blue Hole, Belize. Video courtesy Andy Stockbridge, Belize

   
seahorse dive leader photograph of pilot whales taken from a video Pilot whales Globicephala spp. are actually a type of dolphin, and are commonly known as blackfish. There are only 2 species, a long-finned one living in northern waters and a short-finned one, likely the one filmed here, living in warmer subtropical and tropical areas. Pilot whales feed mainly on squids and fishes. Of all delphinids, pilot whales are exceeded in size only by killer whales. For whatever reason, pilot whales are the cetaceans that commonly strand themselves on beaches - Turneffe Island, Belize. Video courtesy Andy Stockbridge, Belize

   
seahorse dive leader photograph of bottlenose dolphins taken from a video The bottlenose dolphin most often seen in the Caribbean Sea isTursiops truncatus. It represents one of three world species in the genus, the other two mainly inhabiting the Indo-Pacific region. There is a total of some 40 world species of dolphins, in 17 genera. Dolphins feed on fishes that they locate by echolocation. Dolphins communicate with one another using a variety of sounds, flipper and tail slaps, and other forms of body language. They are well known for their sense of "play", as witnessed in this video of them swimming around a dive boat- Turneffe Island, Belize. Video courtesy Andy Stockbridge, Belize

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