Determination of suitable ecological flow regimes for spawning of four major Chinese carps: A case study of the Hongshui River, China

Abstract

Due to the construction and operation of cascade reservoirs in Hongshui River (HSR), most natural fish spawning grounds have been destroyed, thus causing ecological-economic impacts on local riverine ecosystems and fisheries. An effective way to restore spawning habitats and fulfill their spawning requirements is to generate an appropriate ecological flow regime. With a focus on the existing spawning ground of Dingzi Beach (DZB) for four major Chinese carps (FMCC) in HSR, this study built a one- and two-dimensional (1D and 2D)-coupled and fuzzy logic-based fish habitat model to estimate a suitable ecological flow to ensure the existence of continuous and connected habitats. In addition, critical indicators and timing to trigger spawning behaviors were quantified given the requirements for water temperature and high-flow pulses. Thus, suitable ecological flow regimes during the spawning period of FMCC in HSR were established based on the notion of thresholds of flow discharge. The ecological flow between 2,500 and 11,000 m3/s from April to July at DZB was found to be maintained. Three high-flow pulses characterized with different thresholds of flow indicators were recommended to be generated to meet the requirements of the FMCC spawning either in the second half of May, June, or July. Results of this study can provide the basis for sustainably managing cascade reservoirs as well as establishing a suitable ecological flow regime to protect the reproduction of FMCC in HSR.