这里的stocking是stock的动名词,意为“放养”,Freshwater fish stocking就是“淡水鱼放养”,Regular stocking of dams,weirs and rivers则是“对水坝、堤堰、河道的定期放养”.
请看上海译文出版社2007陆谷孙主编《英汉大词典(第2版)》的相关解释和例句:
供给...牲畜;在...放养牲畜(或其它动物);放养
He stocked his farm with Jersey cows.他在自己的牧场里饲养泽西奶牛.
stock a lake (with fish)在湖里养鱼
stock livestock放牧牲口