FOOD wastage caused by hunger striking Vietnamese boat people has prompted the Correctional Services Department (CSD) to introduce a rationing and registration system. Thousands of meals prepared at the Vietnamese camps have been discarded following the asylum-seekers refusal to take food. ''From today onwards we have a system to keep wastage to a minimum,'' a CSD spokesman said yesterday. ''We are asking them to register whether or not they want to eat and then the meals will be cooked according to the number of registrations.'' About 2,500 boat people at the High Island Detention Centre refused ''official'' food yesterday after a similar action by 2,600 on Tuesday in protest against the Government's toughened repatriation policy. Only 67 people from Whitehead Detention Centre refused to eat CSD food yesterday, while about 2,000 demonstrated peacefully, a CSD spokesman said. At Tai A Chau camp, 144 refused official food.