Comparison of the culture performance and profitability of wild-caught and captive pond-reared Chinese mitten crab (Eriocheir sinensis) juveniles reared in grow-out ponds: Implications for seed selection and genetic selection programs

Abstract

Abstract The Chinese mitten crab, Eriocheir sinensis, is a commercially important freshwater crab with a high market value in East Asian countries. The farming of E. sinensis has undergone rapid development in China. Generally, ponds are stocked from two seedstock sources, captive pond-reared juveniles (coin-sized seed, PR) or wild-caught seedstock of E. sinensis (WC). Anecdotally, WC stocks are preferred as they are thought to perform better in culture compared with PR stocks. However, the availability and low cost of PR seedstock have resulted in this becoming the dominant seedstock for production, despite a lack of selective breeding programs. We compared the growth, gonadal development, survival, crab yield, feed conversion rate (FCR), size distribution, and profit between WC and PR populations of E. sinensis seedstock from the Yangtze basin that were cultured in commercial-sized production ponds. The PR had a higher body weight, weight gain rate (WGR), and specific growth rate (SGR) than the WC during the mid-period of the study (July to August) whereas WC had a higher WGR and SGR than PR during the latter part of the study (September to October). Regardless of sex, PR commenced their puberty molt and gonadal development earlier than WC, which resulted in PR having a significantly higher gonadosomatic index (GSI) than WC during the periods between September and November. WC had the higher survival and crab yield, and a lower FCR at the end of the study, though the differences were not significant. However, the proportion of larger sized male or female adults was higher in WC (male ≥ 225 g/crab; female ≥ 125 g/crab) than in PR. The cost of purchasing and feeding WC seedstock was greater than that of the PR seedstock, however the return-on-investment (ROI) for WC seedstock was higher because of higher yield and the higher price for larger crabs. Despite having better culture performance and greater ROI from stocking WC crabs, this source of seedstock is not sustainable for the E. sinensis farming industry because of the variable quantity, high seed cost, and very limited natural seedstock resources in the Yangtze River. Thus, there is a need for genetic-improvement breeding programs focused on the establishment of captive stocks to obtain desirable traits, such as larger harvest size, low FCR, and delayed onset of maturity in E. sinensis.