They are concerned with the decline in production 他们与生产衰退有关。
2.
In 1993 an epidemic outburst of viral disease in 2 . 2 million mu of pond - cultured shrimp brought about a great decline in production in spite of much ameliorative measure taken to improve culture mode and culture technology 1993年，全国范围内220万亩的对虾养殖池爆发了病毒性流行病，产量大减。近几年来，尽管对养殖模式、养殖技术等进行了改革，但我国北方中国对虾的养殖仍然处于低迷状态。
