Fish meal and oil are major components of feed for farmed fish, particularly carnivorous species. Fish meal, however, is a finite resource which cannot be produced in sufficient quantities to sustain the current growth in aquaculture; its rising cost is another cause for concern amongst fish farmers. Research into alternatives to fish meal is now an international research priority and is the focus of current fish nutrition research. Promising results have been obtained using plant (soyabean, rapeseed, corn gluten, wheat gluten, pea and lupin meals) and animal (meat meal, meat and bone meal, feather meal and blood meal) byproduct meals. The latest approach, though not new, is the use of insects as a source of protein in fish diets. The nutritive value of insects as feeds for fish, poultry and pigs has been recognised for some time in China where studies have demonstrated that insect-based diets are cheaper alternatives to those based on fish meal. The insects used are the pupae of silkworms (Bombyx mori), the larvae and pupae of house flies (Musca domestica) and the larvae of the mealworm beetle, Tenebrio molitor. Silkworm pupae are an important component of cultured carp diets in Japan and China. Dried ground soldier fly larvae have been fed to chickens and pigs with no detrimental effects [1-2]. In recent years there has been some interest in the use of housefly maggot meal as a substitute for fish meal in tilapia and African catfish diets [3-6]. Bondari and Shepherd  observed that channel catfish and blue tilapia fed on soldier fly larvae for 10 weeks were acceptable as food by consumers. Growth and organoleptic quality were not affected when common carp were fed on nondefatted silkworm pupae, a major byproduct of the sericulture industry in India . Ng et al.  demonstrated that T. molitor larvae meal was highly palatable to the African catfish (Clarias gariepinus) and could replace up to 40% of the fish meal component without reducing growth performance.
In the March issue of the Journal of the World Aquaculture Society, St-Hilaire and co-workers  describe a study in which they determined if black soldier fly (Hermetia illucens) prepupae and housefly pupae could be used as a partial replacement for fish meal and fish oil in rainbow trout (Oncorhynchus mykiss) diets. Their data suggest that a rainbow trout diet in which black soldier fly prepupae or housefly pupae constitute 15% of the total protein has no adverse effect on feed conversion efficiency over a 9-week feeding period. However, rainbow trout fed on black soldier fly diets low in fish oil had reduced levels of omega-3-fatty acids in the muscle. According to the researchers, modifying the diet of the fly larvae could improve digestibility and fatty acid content of the prepupae, which in turn could enhance the fatty acid profile of the fish fed on the fly prepupae.
The use of the black soldier fly in manure management, yields abundant numbers of fly prepupae. The authors of the study suggest that fly prepupae may be an economical and sustainable feed ingredient for carnivorous fish diets. However, before fly prepupae can be used commercially in rainbow trout diets, a larger trial over a longer period should be conducted to confirm their preliminary results.
The CAB Abstracts database contains some 700 records describing research on alternative protein sources for use in aquafeeds.
 Newton GL, Booram CV, Barker RW, Hale OM, 1977. Dried Hermetia illucens larvae meal as a supplement for swine. Journal of Animal Science 44:395-400.
 Hale OM, 1973. Dried Hermetia illucens larvae (Stratiomyidae) as a feed additive for poultry. Journal of the Georgia Entomological Society 8:16-20.
 Adesulu EA, Mustapha AK, 2000. Use of housefly maggots as a fishmeal replacer in tilapia culture: a recent vogue in Nigeria. 5th International Symposium on Tilapia Aquaculture, Rio de Janeiro, Brazil, Fitzsimmons K, Filho JC, eds, Vol. 1, pp. 138.
 Ajani EK, Nwanna LC, Musa BO, 2004. Replacement of fishmeal with maggot meal in the diets of Nile tilapia, Oreochromis niloticus. World Aquaculture 35(1):52-54.
 Fasakin EA, Balogun AM, Ajayi OO, 2003. Evaluation of full fat and defatted maggot meals in the feeding of clariid catfish Clarias gariepinus fingerlings. Aquaculture Research 34:733-738.
 Ogunji JO, Kloas W, Wirth M, Schulz C, Rennert B, 2006. Housefly maggot meal (magmeal): an emerging substitute of fishmeal in tilapia diets. Deutscher Tropentag 2006, Conference on International Agricultural Research for Development, Stuttgart-Hohenheim, Germany, 11-13 October 2006, 7 pp.
 Bondari K, Sheppard DC 1987. Soldier fly Hermetia illucens L., as feed for channel catfish, Ictalurus punctatus (Rafinesque) and blue tilapia, (Oreochromis aureus) (Steindachner). Aquaculture and Fisheries Management 18:209-220.
 Nandeesha MC, Gangadhara B, Varghese TJ, Keshavanath P, 2000. Growth response and flesh quality of common carp, Cyprinus carpio fed with high levels of nondefatted silkworm pupae. Asian Fisheries Science 13:235-242.
 Ng WK, Liew FL, Ang LP, Wong KW, 2001. Potential of mealworm (Tenebrio molitor) as an alternative protein source in practical diets for African catfish, Clarias gariepinus. Aquaculture Research 32: 273-280.
 St-Hilaire S, Shepard C, Tomberlin JK, Irving S, Newton L, McGuire MA, Mosley EE, Hardy RW, Sealey W, 2007. Fly prepupae as a feedstuff for rainbow trout, Oncorhynchus mykiss. Journal of the World Aquaculture Society, 38:59-67.