Taravana in Pearl Divers
by E.R. Cross
There has been an increasing interest in snorkeling and breathhold diving by recreational divers. This has reawakened an interest in some of the greatest breathhold divers in the world, who earn their living by harvesting products of the sea in deep water. Perhaps the greatest of the breathhold divers are the Paumotan pearl divers of the central Tuamotu Archipelago in French Polynesia. They dive with no surface or self-contained air supply yet are able to descend to depths of more than 120 feet where they work for up to two minutes. In the Tuamotus the pearl divers make eight to ten dives per hour during five to six hours. Frequently, they are stricken by a syndrome they call taravana (tara, to fall and vana, crazily). Recently, David Leith, MD, KN, wrote asking about the timing of the various symptoms in the Paumotan taravana syndrome.
The existence of taravana was first reported in the November 1962 issue of SKIN DIVER Magazine when I revealed my studies of the problem, encountered while diving the Tuamotus. The Paumotan breathhold divers are able to dive deep;to 150 feet and occasionally more. They work at their diving depth for up to one and a half minutes and sometimes make many repeated dives with no more than two to three minute surface intervals. Some taravana symptoms occur early in the diving day; others do not strike until later. The symptoms are easily preventable. One of the likely causes for some of the early symptoms is hyperventilation during the entire surface interval. Later symptoms may be related to short surface intervals between dives.
All snorkelers and breathhold divers should avoid hyperventilation. Experienced and properly equipped snorkelers should not feel the need to hyperventilate. Surface intervals between breathhold dives should be at least five times longer than the bottom time. Bottom time for a snorkeler or breathhold diver counts just as though an air supply was being used. If a snorkeler or breathhold diver remained submerged at 40 feet for one minute, the surface interval would be about five minutes; surface intervals can be less for shallower dives.
Advanced scuba divers sometimes make breathhold dives between scuba dives. Time at depth in the breathhold dive should be added to total bottom time in the repetitive dive tables. Usually, however, it is advisable to relax and rest during a surface interval.
Read the water and read your total projected dive profile. One of the inducements for snorkeling and breathhold diving is the stimulating and exciting nature of marine life in the shallower depths. Readers who are interested in receiving more information on deep breathhold diving and its ramifications as related to scuba diving are invited to write to E.R Cross, c/o SKIN DIVER Magazine, 6420 Wilshire Boulevard, Los Angeles, CA 90048-5515.
In the 1960s and 1970s the Crown of Thorns Starfish (Acanthaster planci) was thought to be destroying, or was likely to destroy, all coral reef systems. Led by some overzealous dive groups and poorly informed science advisers, star-mops and similar eradication methods were common. This scientific misinformation was compounded by some media sources. I also blame scare tactics used by some to benefit their status. In one instance, two scientists spent three weeks flying over the reefs of Guam and determined that reef damage by the starfish was more extensive than had been reported. A Honolulu paper headlined Coral-Eater Starfish Found Here. The next day, UH scientists probe control of starfish. Then the fun started. Divers were organized and began chopping up every Crown of Thorns that was found. Suddenly the destroyers found that some pieces of starfish from the hundreds of chopped up Crown of Thorns were rapidly growing back into adult starfish. Also, there was a report in the New York Times that Shell collecting was tied to the spread of the Starfish. The chief predator of the starfish was supposedly the Tritons Trumpet (Charonia tritonis). Several times I have observed the Trumpet shell feeding on sea urchins, once on a Pincushion Starfish and only once on the Crown of Thorns.
It seems the variations in the population of the rapacious Crown of Thorns are most likely owing to widespread changes in its environment, possibly to some phenomenon such as El Nino. The changes are widespread and slow, rather than local, as would be those caused by shell collecting divers.
Most, possibly all, of the 2,000 species of starfish are carnivorous. During many years of diving in Hawaii, I observed several kinds of starfish feeding. Only once did I observe the Crown of Thorns feeding on coral, although several other divers reported this many times. However, on several occasions, in areas of no coral, the Crown of Thorns was observed feeding on small bivalves, the shells of which they had apparently pried open. On several occasions, the Pincushion Starfish (Culcita novae-guineae arenosa) was observed feeding on small, orange colored, stringy sponges. The long-rayed stars, principally those in the Solaster family, are noted for their rapacious feeding on heavily coated pier pilings. The suction cups on the many arms of these stars pry open the shell, feed on the mollusk and then let the shell fall to the bottom. The Sunflower Star (Pycnopodia helianthoides) is very mobile compared to others. Other seastars feed on sea anemones and still others on sea urchins. Seastars that live buried in soft mud probably feed on worms and other animal life that exists in this habitat.
Read the Water
Last month we addressed the question, Can an environment be destroyed? An environment is the aggregate of influences or forces surrounding a habitat that may influence or modify organisms in their form and potential for survival. It is my opinion that an environment can only be changed, not destroyed. No matter how an environment is changed there will be an aggregate of something to influence organisms in the area.
The question then arises, Can a habitat be destroyed? A habitat is a site or place having physical features where plant or animal species naturally exist and grow, or where entire populations of similar or related biota thrive. Again, I feel a habitat cannot be destroyed; it can only be changed. Possibly the change can be so dramatic that some species occupying the habitat will either die or migrate to a more suitable habitat. However, something will very quickly occupy the disturbed habitat and will continue to exist and grow.
As a diver, your environment is the surrounding water. When you touch bottom you will establish a habitat, albeit a small, temporary one. As you dive your way around the world read the water and all it encompasses. You will be surprised at what you find. Small ecological niches and biotopes will hold as many exciting and pleasant surprises as shark feeding areas. Go for it. You will be glad you did.