Although many kinds of edible fish are readily obtainable in New Zealand waters, the fishing and fish-processing industry has remained relatively small. Since the 1960s, however, the government has taken a number of measures to expand the industry and increase fishery exports. In 1978, the government began implementing a 322-km (200-mi) exclusive economic zone. During the next four years, it approved nearly 40 joint ventures with foreign companies in order to exploit the zone, which, with an area of about 1.3 million sq mi (nautical), is one of the world's largest. These waters support over 1,000 species of fish, about 100 of which have commercial significance. The volume of fish landed in New Zealand increased from 6,488 tons in 1936 to 561,324 tons in 2000. New Zealand's domestic vessels account for about 60% of the catch. With the rapid growth of fishing in the 1980s, about 75% of the catch is exported (with a value of $665.7 million in 2000), mostly to the United States, Japan, and Australia. The principal finfish species caught included blue grenadier, mackerel, whiting, snoek, and orange roughy. In addition, New Zealand fishermen in 2000 landed 20,952 tons of squid and 15,319 tons of New Zealand dredge. The most valuable part of the catch is made of orange roughy, hoki, squid, and rock lobster. Oyster and mussel aquaculture are well established; scallop, salmon, and abalone farming are developing. In 2000, exports of fish and shellfish totaled NZ $84 million; Australia, Japan, and the United States were the major markets.