Round Stingray, Urolophus halleri
The round stingray (Urolophus halleri) is found in coastal waters in the eastern North Pacific Ocean. It is most common around southern California and the Baja Peninsula, but can also be found from Humboldt Bay south to Panama.
The round stingray prefers warm-temperate waters close to shore less than 49 feet deep. However, some have been spotted to depths of 298 feet. They are a bottom-dweller found in muddy or sandy floors with an abundant supply of eelgrass which they can camouflage themselves in. They may also be found around rocky reefs.
Prevalent water temperature for this species is 50 degrees Fahrenheit. The adults can withstand a wider range of water temperature than the juveniles. From spring to fall they stay close to shore but in the winter they move to deeper water where the temperature is more consistent.
The shape of the disc is nearly round. It has a short stout tail with a long serrated stinging spine. Inside the mouth are small diamond shaped teeth. In males the central teeth are sharply pointed and curved inward. The color of the round stingray can be brown, black or grayish with pale yellow spots, some individuals are spotless. The tail spine is shed and replaced periodically. At the beginning of July a small second spine appears and the species has two until the primary one falls off, usually around September.
The male and female of this species usually segregate. The male stays close to shore while the female is in deeper water. Juveniles feed on polychaete worms and crabs. As they mature they begin to feed on mollusks. Round stingrays feed during the day and are most active during the warmer temperature of summer. They use their disc and mouth to uncover buried prey.
The female will birth one to six young, with amount being determined by the size of the female. The gestation period is three months and the female stores sperm year-round. Mating is done from April to June in southern California and later in the year further south. The females migrate closer to shore with the males. After the young are born, the female will swim back into deeper water and the juveniles stay in the shallows.
Hundreds of beach goers are stung yearly by the round stingray. Though it is not fatal, it is very painful. An average of 226 people are stung yearly on Seal Beach. Authorities have recently begun capturing, tagging and removing the spine to reduce injuries to swimmers. But it has not been successful due to the large number of round stingrays and their natural ability of stinger replacement.
They are considered a nuisance by trawlers, caught in large numbers in their nets. Usually they are discarded or have the tail removed resulting in a high mortality rate. Due to the abundance of the species and high reproduction rate, the International Union for Conservation of Nature has them listed as least concern.
Image Caption: Round stingray (Urolophus halleri). Credit: LASZLO ILYES/Wikipedia (CC BY-SA 2.0)