Fish actually seem to prefer housefly larvae and pupae over fish meal, meaning they grow faster when fed with the product, a study has shown. In addition, fish that were raised using the product were less prone to catching diseases, as substances contained in the larvae and pupae apparently strengthen their immune system.
Also, farmed sea bream and yellowtail that were fed the maggots and pupae boasted a glossy coat similar to those found in the wild, unlike those that grew up eating fish meal.
Takeshi Miura, 54, a professor of fish reproductive physiology at Ehime University's South Ehime Fisheries Research Center in Ainan, Ehime Prefecture, has been studying how to farm fish by feeding them insect-derived products since 2008.
Today, many fisheries use fish meal as fish feed, but the material is prone to price hikes and there is a worry that it could place a greater burden on precious marine resources.
Miura believes the use of houseflies gets around this.
The researcher has been experimentally growing the insect in a facility he set up in a pig farm in Kagoshima Prefecture in 2014.
The research center is located in the Nanyo area, the western part of Ehime Prefecture facing the Bungo Channel, which is home to many fish farms raising sea bream and yellowtail, both important commercial species.
The study was spurred by a local resident looking after such aquacultures whom Miura heard complain that “it’s tough dealing with the constant rise in fish meal prices.”
Fish meal is a powder made from anchovies among other fish, but diminishing catches due to overfishing and climate change have led to price increases.
A kilogram of the fish meal was imported for about 100 yen (US 88 cents) in 2012, but the same amount fetched 285 yen two years later. Currently, it goes for about 140 yen.
In addition, experts have criticized that using mass amounts of anchovies as fish feed was wasteful, especially with rising fears of a global food shortage.
So then what rich source of protein could replace anchovies? What came to Miura’s mind were houseflies--a readily available insect species that can be multiplied rapidly.
Upon kicking off the research, the professor found that flies were a better choice than other insects, as all maggots need to grow are waste products. Ten kg of manure acquired from pig farms can be turned into 1 kg of larvae and 3 kg of fertilizer, meaning the pig manure requires no waste treatment.
Miura estimates that the total amount of manure produced from pig farms in Kagoshima and Miyazaki prefectures in a year would be enough for maggots to replace 30 percent of the fish meal circulating annually in the nation.
Fly larvae and pupae seem to enjoy a significant advantage over fish meal, but they are not without obstacles. The biggest issue would be the gross-out factor, as both consumers and farmers rarely perceive flies as the most sanitary of creatures.
Still, Miura remains hopeful.
“By using fly larvae, we will be able to produce foodstuff without adding stress to the environment,” he said. “We hope to establish the technology to farm the maggots in few years’ time.”
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