Feeling the Sting

Coastal degradation is concentrating stingrays along healthy beaches, where they can make visitors painfully aware of their presence

• Michael Tennesen
• Aug 01, 2005

ABOUT 30 BIOLOGISTS and graduate students from California State University–Long Beach splash into the surf at Seal Beach and take hold of the ropes at either end of a 100-foot seine net that loops out into the sea. They strain at the ropes, hoping to land whatever marine treasures the white water hides. Once on shore, they dump the wiggling contents onto the sand. They quickly toss fish back into the water, but one common catch—stingrays—they handle more gingerly, carrying them carefully by the tail to plastic pools filled with water, where they will be measured and marked.

In less than 20 minutes on this July day, Chris Lowe, an associate professor of marine biology at Cal State, and his colleagues have pulled more than 300 stingrays from the water. According to Lowe, the rays, with their venomous stingers, pose an invisible danger to Southern California surf enthusiasts. “In the summer, Seal Beach attracts hundreds of unwary beach goers each day who trot into the surf and the next thing they know, they are in a minefield,” he says.

Lowe is the head of the Cal State Shark Lab, where he studies rays, skates and sharks, related animals collectively known as elasmobranchs. He believes that the density of stingrays at Seal Beach, and the problem it poses for people, is an example of the dire condition of the marine environment off Southern California, a region plagued by pollution and habitat loss.

In the United States, stingrays nail their barbs into 1,200 to 1,500 people every year. About a quarter to a third of these incidents occur on tiny, mile-long Seal Beach. During summer, lifeguards keep a row of buckets filled with hot water so beach goers can soak their wounds to help neutralize the stingray venom. As many as 20 people gather there at once on busy summer days to tend their injuries. Allergic reactions, stingers that break off in the flesh, severe cuts and infections can send victims to the hospital.

An average stingray spine measures about 1 and 1/2 inches long. The needlelike point allows the ray to drive it into the flesh of beach goers, and miniature teeth along the edges hold the stinger in place. “When you pull it away, the teeth act like a steak knife sawing away the flesh—it can sever a tendon,” Lowe says. “But it is the mucous covering over the stinger that contains the venom which causes the pain.”

California has several species of stingray, including the bat ray, which can grow up to 6 feet long, but the animals that cause the most problems for people are the dinner-dish-sized round rays. These animals occupy Seal Beach waters from May to October, but the highest number of stinging incidents occurs during summer when schoolchildren hit the beach.

Most stingrays move off when approached, but round rays bury themselves in the sand where they are difficult to detect. “Once someone steps on one, it flips its tail up as reflex, and it sticks in your foot or calf,” says Lowe, who has been stung several times. “The pain is like something you wouldn’t believe.”

The local community has tried culling, fishing derbies and translocations to control the problem, all to no effect. Signs on lifeguard stations warn bathers of the dangers and encourage them to shuffle their feet while in the water in order to scare off stingrays hidden under the sand.

Lowe and his colleagues started work in 2000, tagging stingrays to estimate population size. The first year they tagged 2,200 stingrays but recaptured only 14 after two years, indicating a minimum summer population off Seal Beach of 16,000.

Round rays have a life expectancy of 10 to 12 years. Sexually mature at 3 to 4 years, they mate in May and give birth in September or October. They feed on clam necks, marine worms and soft-shelled creatures. Stingrays use shallow estuaries as important mating and pupping grounds. They forage in the sediment and perform an important function by stirring up the bottom, re-suspending nutrients so that shellfish and other marine organisms have access to them.

To date the shark lab has captured, measured and tagged more than 6,000 rays at Seal Beach. A combination of ecological problems makes the beach especially attractive to round rays. Breakwaters to the north tame the surf, keeping waves from flushing away the fine silt that round rays prefer as a substrate. Two power plants discharge warm water into the nearby San Gabriel River, creating an artificial estuary at Seal Beach.

Pollution is a key problem along the Southern California shore, where toxic waters have contributed to a decline in fish that prey on stingrays, a further boost to the rays. Cities use the coastal rivers for drainage, pouring in pollutants. Eighty-five cities feed storm drainage into the San Gabriel River. Seal Beach is frequently closed to swimmers when bacterial levels rise because of animal feces that enter the storm-drain system. This pollution jeopardizes a number of coastal species, including hornyhead turbot, sheephead and halibut.

Kevin Kelley, a research endocrinologist at Cal State, is looking at the effects that human hormones in sewage may have on marine species. Modern sewage treatment facilities do a lot to clean up urban effluent, but they cannot touch many of the substances that are excreted with urine, such as estrogen.

Kelley has found that levels of estrogen in hornyhead turbot near sewage outfalls are ten times higher than those found elsewhere. Hormones like estrogen can play an important part in fish development. Bottom fish such as turbot and sole are born with eyes on either side of their heads, as in other fish. But in these species, one eye migrates to the opposite side as the fish matures and “flattens,” allowing it to lie close to the ocean bottom. Kelley is studying what effect elevated hormones may have on development. Studies elsewhere show that elevated hormones can impair both growth and stress-response systems.

Sewage outfall problems and wetlands development affect marine populations nationwide, particularly near major population centers on the east and west coasts. Studies in Brazil, Canada and Italy show similar problems. “No major population center is immune to them,” says Kelley.

There are a few bright spots along the Southern California coast. Native grasses have filled in parts of Mission Bay off San Diego, yielding “the most important fish nursery in Southern California,” according to biologist Dick Seymour at the Scripps Institution of Oceanography. Remediation efforts mandated by the expansion of commercial harbors have improved a number of coastal lagoons, which had filled with sediment from development.

Chris Lowe says some environmental groups have been trying to get the breakwater off Long Beach, north of Seal Beach, removed in order to return the coastline to a more natural condition. Though he thinks that will be a tough fight, he sees more immediate progress elsewhere. Locals are learning the stingray shuffle. Says Lowe, “People do not call for the wholesale killing of the rays anymore. They are learning to coexist.”

Michael Tennesen is the author of The Complete Idiot’s Guide to Global Warming.



What to Do If Stung by a Stingray

Remove the stinger if present and control bleeding by applying pressure to the wound as needed.
Wash the wound immediately with available water.
As soon as possible, immerse the wound in water as hot as the victim can stand. The heat will relieve pain.
Disinfect the wound after removal from hot water.
Seek medical help as soon as possible—even seemingly harmless stings can damage tissue.