Freshwater fishes

Abstract Freshwater (FW) aquaculture has greater potential than mariculture for intensifying production in ecologically sustainable systems that utilize available know-how and technologies. FW fishes used for aquaculture are positioned lower in trophic webs and, thus, require fewer resources than most catadromous, anadromous, and marine aquaculture fishes. Carp, tilapia, and catfish are the most important FW fishes used for aquaculture. They are farmed mostly in semi-intensive, open pond systems that rely heavily on ecosystem services. FW fish aquaculture is often divided into hatchery, nursery, and grow-out phases. Reproduction of carp, tilapia, and catfish broodstock is performed by natural spawning or artificial fertilization. In carp and catfish, injection of pituitary hormones induces ovulation and spawning. Carp and tilapia species dominate animal aquaculture and are often raised in polycultures to better utilize resources by taking advantage of different feeding habits and food preferences. Polyculture of carp and tilapia with rice and azolla improve resource utilization by integrating primary producers with heterotroph consumers into aquaculture nutrient cycles. Tilapia, carp, and catfish have high environmental stress tolerance and are ideal for a wide variety of aquaculture systems. However, their high environmental stress tolerance also promotes invasiveness. Premature reproduction of tilapia is problematic for aquaculture and promotes invasiveness. It has been addressed by producing single-sex (mostly all male) populations using multiple approaches. Catfish aquaculture has shifted from an initial focus on channel catfish in the second half of the twentieth century to Asian torpedo and shark catfish, which have superseded channel catfish in value and yield.