Changes in Abundance of Larvae of the Four Domestic Chinese Carps in the Middle Reach of the Yangtze River, China, before and after Closing of the Three Gorges Dam

摘要

In 1997 - 2005, a systematic study on the dynamics of the abundance the larvae of the four domestic Chinese carps was performed in the middle reach of the Yangtze River, close to Sanzhou city. It was calculated that in breeding seasons the abundance of fry drifting through the section of Sanzhou was 3. 59 billion in 1997, 2. 75 billion in 1998, 2. 15 billion in 1999, 2.85 billion in 2000, 1.90 billion in 2001, 1.90 billion in 2002, 406 million in 2003, 339 million in 2004 and 105 million in 2005 respectively. Spawning locations of the four domestic Chinese carps in the middle reach of Yangtze River were almost the same, but larval abundance was lower since 2003 (before the Three Gorges Project was closed). The composition of larvae has undergone great changes compared to 1970s. The proportion of silver carp increased, but the proportion of grass carp descended obviously, which indicated that the affect of the Three Gorges Project is grave to grass carp.