Improvement of fish and pearl yields and nutrient utilization efficiency through fish-mussel integration and feed supplementation

A 153-day experiment was conducted in land-based enclosures to explore the efficacy of fish-mussel integration in pearl yield, fish yield and nutrient utilization. The freshwater mussel Hyriopsis cumingii were integrated with either a four-fish species combination (grass carp, gibel carp, silver carp and bighead carp) or a two-fish species combination (silver carp and bighead carp). Fish in each combination received either formulated feed supplementation or no formulated feed. Fish yield, nitrogen utilization efficiency and wastes of nitrogen and phosphorus were higher in the enclosures received formulated feed supplementation than in those received no formulated feed. Production performance (evaluated with pearl weight and soft tissue weight of each mussel, pearl and fish yields, nitrogen utilization efficiency and nitrogen wastes) was better in the enclosures of mussel integrated with four fish species and fed with formulated feed than in those of mussel integrated with two fish species without feeding formulated feed. The total nitrogen, total phosphorus, chemical oxygen demand and calcium in the water column were higher, while the Secchi depth and dissolved oxygen were lower, in the enclosures stocked with four fish species and fed formulated feed than in those stocked with two fish species and without feeding formulated feed. This study indicates that formulated feed supplementation to a fish-mussel integrated system can enhance fish and pearl yields and nitrogen utilization efficiency. The combination of four fish species with complementary feeding habits is more productive than that of two fish species in a fish-mussel integrated system. Statement of relevance: We declare that: 1. This study is original and has not been published elsewhere. 2. All data involved in the manuscript are checked and reliable. 3. All the authors have read and accepted the manuscript as it is submitted. 4. All the authors approve the version to be published. We declare that nobody who qualifies for authorship has been excluded from the list of authors. (C) 2015 Elsevier B.V. All rights reserved.