Aquaculture industry development, annual price analysis and out-of-season spawning in largemouth bass Micropterus salmoides

Largemouth bass (LMB) is one of the two fastest-growing fish species and viewed as one of the five most successful alien species in Chinese aquaculture. Global aquaculture production of LMB reached 0.458 million tons in 2017 and China produced 99.8% of the total amount. Currently, imbalanced regional production, strong price fluctuation, and universal poor seed quality are three main stumbling blocks for steady and healthy aquaculture industry development of LMB. In the present work, we have analyzed interannual and seasonal price volatility between 2015 through 2018 and the production mode of LMB and concluded that off-season spawning is one of the best solutions for these issues. We have established an off-season spawning regimen for LMB through a single manipulation of temperature, which is suitable for large-scale production of LMB fry in the autumn (September and October). We also found as a species displaying a mixed-breeding (capital breeding and income breeding) strategy, LMB is able to acclimate itself rapidly to compressed reproductive cycle using different energy allocation strategies. Our results combined with previous reports suggest photoperiod is more important for the process of oogenesis in LMB, while the temperature is more critical for vitellogenesis and the final stage. The off-season spawning technique allows us to produce LMB fry twice in a year using the same broodstock population by single temperature manipulation.