Decreasing global availability of fish meal or fish oil has urged the aquaculture industry to investigate the alternative ingredients.Exploring the dfferences between fish meal or fish oil and their substitution is particularly important.And one of the main differences is whether highly unsaturated fatty acids(HUFAs)exist and their content.HUFAs are the fatty acids that contain no less than 20 carbon atoms and 3 double bonds,which play important roles in supplying energy for fish organism,moderating the membrane compositions,converting to the highly biological eicosanoids,as well as regulating the lipid metabolism and immune response,mainly being contained in fish oil and certain kinds of microalgae.It is acknowledged that freshwater fish has the capacity to synthesize HUFAs de novo,thus HUFAs were not the essential fatty acids and there is no need to be included in the diets.However,considerable researches have proved the nutritional benefits of HUFAs in the freshwater fish,suggesting that the fatty acid theories of freshwater fish remained to be further improved.This paper reviewed the recent results about the effects of HUFAs on the growth performance,lipid metabolism,health status,immunity and reproductive performance of the freshwater fish,indicating that HUFAs should be supplied in diets for the cultured freshwater fish,especially in the context with the use of less-HUFAs-contained protein or oil sources.The role of dietary HUFAs for freshwater fish should be noted in the future studies.Finally,the prospects of future research on HUFAs requirement of the freshwater fish as well as new HUFA-enriched oil source development have been discussed.