长鳓（学名：Ilisha elongata，又称鳓，俗名曹白、鲞鱼、力鱼）为辐鳍鱼纲鲱形目鲱亚目锯腹鳓科鳓属的其中一种鱼类。

本鱼广泛分布于东海、俄罗斯东部大彼得湾以及沿海，以及印度太平洋区等海域，包括俄罗斯远东地区、日本、朝鲜、韩国、台湾、印尼、马来西亚、印度、缅甸、泰国、越南、菲律宾等。该物种的模式产地在苏门答腊。

Ilisha elongata, called the elongate ilisha (the FAO name) or Chinese herring or slender shad (even though it is not a close relative of herrings and shads) (Chinese:勒鱼; pinyin:lèyú, or simply 鳓, lè), is a species of longfin herring native to the coastal waters and estuaries of North Indian Ocean and Northwest Pacific. It is a relatively large species, up to 45–60 centimetres (18–24 in) in total length. It is an important fishery species.