High-priced sweet water prawns a large type of shrimp — are being grown in Israel and have become a fast-growing export — though none are sold locally because of the kashrut laws. Israel grows and markets locally some 10,000 tons of fresh-water fish in fish ponds annually. The prawns were first introduced to diversify the fish population, and exports began two years ago, when 3.5 tons were sent abroad. The exports doubled last year to seven tons, and this year the breeders plan to export 16 tons, at $6,000 a ton. The prawns are hatched in laboratories, introduced to the ponds in April and grow to marketing size of 45 grams by November.