Some of the class stands by the Sundial at the Lighthouse on San Salvador, Bahamas. See other beautiful phenomena from the Bahamas.
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Southern stingrays are one of the many types of rays belonging to the class chondirchthyes along with sharks and chimeras. They are also one of the 513 species included in the order rajiformes, belonging to the stingray family Dasyatidae. The other families in this order consist of Urolophidae (round rays), Narcinidae (electric rays), and Potamotrygonidae (freshwater stingrays). Southern stingrays are scientifically named Dasyatis americana.10
Southern stingrays are found most commonly in the Atlantic Ocean, from New Jersey through the Gulf of Mexico and the Caribbean to Rio de Janeiro, Brazil. They live in shallow, inshore open water with sandy or muddy bottoms that provide excellent camouflage. Based on this habitat, these rays feed primarily on small fish, shrimp, crabs, clams, and worms. The Southern stingray is easily recognized by its diamond shaped body that can reach up to seven feet in length. The body has distinct pointed edges as well as a light colored forehead spot. Additionally, Southern stingraysÕ have a gray or a white underside, but are capable of changing the skin on their back between gray, brown, or green in order to best match their surroundings. 10
Despite their attempts to blend in, Southern stingrays have been observed to have symbiotic relationships with other marine animals. The most prevalent of these is their cleaning interaction with the bluehead wrasse. Southern stingrays are frequently noticed to be swimming slowly around a cleaning station while the wrasses nip at their dorsal side or to be cleaned when they settled on the cleaning station and assumed the solicitation pose.9 Another more rare interaction has been observed between a Southern stingray with an octopus attached to the rayÕs back. The reasons for this attachment are unclear, but it is hypothesized as a means of travel for the octopus, a technique to avoid predation by the stingray, or for feeding on the stingrayÕs mucus.11
Although Southern stingrays are non-aggressive, they are probably best known for the painful effects of their sting. In fact, stingray stings result in approximately 1,500 emergency room visits annually in the US, which is more than any other marine vertebrate. The majority of stings occur when a swimmer steps onto a stingray hidden in the sand, typically in shallow water. This causes the stingray to feel threatened and triggers the stingray to whip its tail around against the victimÕs leg or foot. The painful sting originates from the stinger enclosed in a sheath on the tail that is equipped with 1-4 venomous spines. 1, 13
Once skin has made contact with the stinger venom, the immediate result is intense localized pain. However, the venom can also potentially result in salivation, nausea, vomiting, diarrhea, syncope, muscle cramps, fasciculations, dyspnea, cardiac dysrhythmias, hypotension, seizures, convulsions, and rarely, death. Every individual can react differently to the venom, so one should be carefully monitored for any of the more serious previously listed conditions. The venom is known to be heat labile and composed of a variety of proteins, enzymes, and serotonergic and cholinergic substances, yet the exact component that causes the severe symptoms and pain still remains unclear. 1, 13
Immersing the affected area in hot water is thought to eliminate or significantly decrease the pain associated with the sting by accelerating the denaturing of the venom toxin. In a retrospective study of 119 cases admitted to the emergency room, 88% of patients experienced total pain relief within 30 minutes with strictly a hot water immersion treatment. The rest of the patients experienced complete pain relief upon the single dosage of an analgesic, and none experienced any thermal burns or similar negative side effects due to the treatment. However, a significant number of patients returned to the emergency room with wound infections due primarily to the puncture nature of the wound. Therefore, in addition to the hot water immersion, it is suggested that the afflicted individual should be prescribed antibiotics to prevent serious infection.1, 13
Despite their stinging potential, Southern stingrays manage to attract thousands of tourists every year to areas such as the ÔÔStingray City SandbarÕÕ in the Cayman Islands. This is a warm, shallow area located in the North Sound of Grand Cayman, where free-ranging Southern stingrays gather to be hand fed frozen squid.8 With environmental and wildlife preservation becoming the latest fad, marine wildlife tourism (MWT) has become one of the biggest money makers for countries with coastlines.2 Ultimately, MWT has both positive and negative effects on the animal involved. The greatest benefit in the exploitation of wild animals is the interaction typically promotes awareness and appreciation of species, which creates an increased desire in the tourist to protect the speciesÕ natural environment.8
Unfortunately, MWT can also have several negative affects on the species, especially if careful management techniques are not practiced. Frequently, the ideals of the wildlife conservationalist, the visitor, and the money-making stakeholder clash, with the wildlife conservationalist often being the losing party.5 In these instances, the wildlife regularly becomes dependent on the tourists as their primary food source, which can differ significantly from their natural diet as well as lead to food shortages and starvation during tourist off-seasons. During these times, inter-species aggression and accidentally injury of the tourist is more likely to occur as the animals struggle to survive. The deviation from the animalÕs intended diet can also make it more susceptible to increased injury and disease. Ultimately, intentional and long-term feeding can alter the natural behavior patterns and populations levels of any animal.5
In the case of the Southern stingrays, a recent study involving fatty-acid (FA) profiling was commissioned by Caymanian stakeholders in order to determine the compositional and nutritional requisiteness of the fed animalsÕ diet as compared to free-foraging Southern stingrays. Since FAs take longer to incorporate into the animal, FA profiling provides a more complete picture of the animalÕs diet, as opposed to the snap snots provided by direct observation of dietary intake, stomach content, and scat analysis. Profiling results indicated significant differences in serum FA composition between the unfed and fed Southern stingrays, with the FA profile of the fed stingrays more closely resembling that of squid.8
Ultimately, this indicates that the squid has become the major food source in these stingraysÕ diet, suggesting that humans have now become the primary provider and possibly that these stingrays are losing their natural ability to forage. Additionally, such results indicate that fed stingrays are more likely to have a lower body condition which could cause long-term effects on the fed stingraysÕ growth, immune function, resistance to parasites and disease, and overall survival.8 Furthermore, a different study found that fed Southern stingrays were more likely to be injured by boats and predators, be susceptible to ecto-dermal parasites, be engaged in intense interference competition (in the form of conspecific bite marks), and have a higher mean numbers of injuries, parasites, and median bite marks.9
In order to limit these negative impacts as much as possible, several management techniques have been suggested. Wildlife conservationalists advise decreasing the amount of artificial food fed to the Southern stingrays or change the composition of the supplied food so that it more closely resembles the variety found in the Southern stingrayÕs natural diet. It is also suggested to implement management techniques that limit boat and stingray density in order to control crowded conditions at tourist sites.8
Such suggested management techniques raise concerns from wildlife tourism managers over how tourists would respond to the proposed wildlife management plans. In order to predict this response, a survey consisting of hypothetical wildlife viewing experiences was conducted on a sample of visitors to the Stingray City Sandbar. Responses fell into two distinct categories, two thirds being pro-management and the remaining being pro-current. Those falling under the pro-management category desired actions that reduced congestion, impacts on stingrays, and the number of stingrays present. They also were willing to pay a conservation fee and were primarily concerned with significantly reducing the risk of injury to the rays.6
In the pro-current group, the tourists would be willing to pay a small conservation fee, but were most strongly interested in continuing to directly interacting with the stingrays, even if it meant engaging in potentially injurious activities. This group was not concerned with congestion, as they felt the excitement of the experience would be diminished if the number of stingrays was limited. Despite this, both of these groups responded positively to at least some form of wildlife management. This suggests that some techniques could be implemented to successfully manage the exploitation of the Southern stingrays.6
Regardless which technique the manager chooses to follow, it is clear that some form of action is necessary in order to maintain the health of the Southern stingrays. Although Southern stingrays may not be endangered of extinction like pandas or bald eagles, they are endanger of becoming a menace to society much like the bears at Yellowstone National Park. In the recent years alone there have been two documented cases of stingrays jumping into fishing boats and injuring the occupants.12 Although these seemed like freak events, it is unusual for a stingray to come into such close contact with boats and one cannot help but wonder whether this was the stingrayÕs attempt to gain food from a place it had been conditioned to associate as a food source. With increased human contact at places like the Stingray City Sandbar, it seems only likely that such events will occur more frequently in the future as the battle for a food supply becomes more intense. With the public so focused on saving the environment, there has never been a more opportune time to implement wildlife management techniques for Southern stingrays. Ultimately, each individual manager will need to determine which techniques are most appropriate for their stingray population.
Works Cited
1Clark, R. F., Girard, R. H., Rao, D., Ly, B. T., & Davis, D. P. (2007). Stingray envenomation: A retrospective review of clinical presentation and treatment in 119 cases. Journal of Emergency Medicine, 33(1), 33-37.
2Green RJ, Higgenbottom K (2000) The effects of non-consumptive wildlife tourism on free-ranging wildlife: a review. Pacific Conservation Biology 6:183Ð197
3Orams, MB. (2002). Feeding wildlife as a tourism attraction: a review of issues and impacts. Tourism Management, 23, 281-293.
4Rays (2008). In Lerner B., Lerner K.(Eds.), . Detroit: Thomson Gale.
5Reynolds PC, Braithwaite D (2001) Towards a conceptual framework for wildlife tourism. Tourism Management 22:31Ð42
6Semeniuk, C.A.D., Haider, W., Beardmore, B., and Rothley, K.D. (2009). A multi-attribute trade-off approach for advancing the management of marine wildlife tourism: a quantitative assessment of heterogeneous visitor preferences. Aquatic Conservation, 19(2), 194-208.
7Semeniuk, C.A.D., Rothley, K.D. (2008). Costs of group-living for a normally solitary forager: effects of provisioning tourism on southern stingrays Dasyatis americana. Marine Ecology Progress Series, 357:271-282.
8Semeniuk, C.A.D., Speers-Roesch, B., Rothley, K.D. (2007). Using Fatty-Acid Profile Analysis as an Ecologic Indicator in the Management of Tourist Impacts on Marine Wildlife: A Case of Stingray-Feeding in the Caribbean. Environmental Management, 40(4), 665Ð677.
9Snelson, F.F., Gruber, S.H., Murru, F.L, Schmid, T.H. (1990). Southern Stingray, Dasyatis americana: Host for a Symbiotic Cleaner Wrasse. Copeia, 4, 961-965.
10Southern stingray. (n.d.). Retrieved April 28, 2009, from EBSCO Animals database.
11Souza, A.T, Ilarri, M.I., Valentim, L.P.F (2007). A Ôhitch-hiker octopusÕ on a southern stingray at Fernando de Noronha Archipelago, SW Atlantic. Coral Reefs, 26:333.
12Sutton, J. (2008, March 21). Stingray barb 'did not kill woman.' Retreived from 13Vijayasekaran, V.J. (2001). Stingray Envenomation or Iatrogenic Thermal Burn. ANZ Journal of Surgery, 71, 323Ð325.
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