aggregation, swimming and respiratory behaviour of sharks, but only at short time scales. The group size of scuba divers was less important in affecting sand tiger behaviour than the distance within which they approached the sharks. Divers approaching to within 3 m of sharks affected their behaviour but after the divers had retreated, the sharks resumed normal behaviour. Other studies indicate sand tiger sharks can be indifferent to divers. Scuba divers are normally compliant with Australian shark-diving regulations. In captivity Its large and menacing appearance, combined with its relative placidity, has made the sand tiger shark among the most popular shark species to be displayed in public aquaria. However, as with all large sharks, keeping them in captivity is not without its difficulties. Sand tiger sharks have been found to be highly susceptible to developing spinal deformities, with as many as one in every three captive sharks being affected, giving them a hunched appearance. These deformities have been hypothesized to be correlated to both the size and shape of their tank. If the tank is too small, the sharks have to spend more time actively swimming than they would in the wild, where they have space to glide. Also, sharks in small, circular tanks often spend most of their time circling along the edges in only one direction, causing asymmetrical stress on their bodies. Threats and conservation status Threats There are several factors contributing to the decline in the population of the sand tigers. Sand tigers reproduce at an unusually low rate, due to the fact that they do not have more than two pups at a time and because they breed only every second or third year. This shark is a highly prized food item in the western northern Pacific, off Ghana and off India and Pakistan where they are caught by fishing trawlers, although they are more commonly caught with a fishing line. Sand tigers' fins are a popular trade item in Japan. Off North America, it is fished for its hide and fins. Shark liver oil is a popular product in cosmetic products such as lipstick. It is sought by anglers in fishing competitions in South Africa and some other countries. In Australia it has been reduced in numbers by spear fishers using poison and where it is now protected. It is also prized as an aquarium exhibit in the United States, Europe, Australia and South Africa