Studying the variation of cross-section vorticity on the spawning grounds of the four major Chinese carps in the middle reach of the Yangtze River

摘要

The four major Chinese carps, the grass carp (Ctenopharyngodon idella), black carp (Mylopharyngodon piceus), silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis), are typical pelagic spawners. With reproductive modes stimulated by peak ood dynamics, their spawning grounds in general are located at riverbanks or in areas of complex terrain that form ‘reduced or vortex ows’, thereby ensuring good conditions for fertilization and egg development (Yi, 1988). Yang et al. (2007) studied this topic on sturgeon spawning grounds. However, complex hydrological conditions are dicult to measure because of limited analytical techniques. One research approach at present is to identify characteristics of spawning grounds via hydroacoustics (Li et al., 2006; S. Y. Wang et al., 2008; Y. K. Wang et al., 2009).