This post belongs to a series written by students in the Conservation Biology course BSC4052 at the University of South Florida. This course provides an overview of major themes in conservation practice and related applied problems in biology, including: population ecology in the context of conservation, patterns of diversity, valuing diversity, threats to diversity, management actions and strategies for preserving diversity.
Kevin Riemensperger is currently a senior at the University of South Florida; pursuing a bachelor’s in Animal Biology. An avid swimmer; he has always been interested in the water, and that passion extends into his love of Florida’s freshwater and marine ecosystems. He dreams of a world where people practice sustainability in all aspects of their lives. Upon graduation, Kevin plans to pursue conservation work in Florida, and to protect the many forms of life that amaze him.
Primary Article: Vongvichith, B., Morioka, S., Sugita, T., Phousavanh, N., Phetsanghanh, N., Chanthasone, P., Pommachan, P., Nakamura, S. 2020. Evaluation of the efficacy of aquaculture feeds for the climbing perch Anabas testudineus: replacement of fishmeal by black soldier fly Hermetia illucens prepupae. Fish Sci 86: 145–151. https://doi.org/10.1007/s12562-019-01381-5
Featured Image: A handful of young climbing perch; the fish investigated in this groundbreaking study. Source: Southeast Asian Fisheries Development Center/Aquaculture Department
You Are What You Eat
Farmed fish need diets high in protein if humans want them to grow fast and large. Sometimes up to 40% pure protein! Today, the protein needed to feed farmed fish is mostly made by grinding up smaller fish. This ground up fish product is called “fishmeal”, and it’s often the number one ingredient used in the diets of aquaculture fish (Péron et al., 2010). This is an issue, since the fish used for fishmeal could be fed to people instead. Additionally, harvesting all those small fish harms existing fish populations. Between humans, their livestock, and the wild animals that depend on those fish stocks, these populations are dwindling.
Bugs to the Rescue!
On a planet with a growing number of mouths to feed, solutions are needed to relieve pressure on wild fish populations. Numerous past studies have been done to find alternative sources of protein for fish-diets, including plant sources like soybeans, or animal sources like chicken meal. Among these alternate sources, the black soldier fly shows promise, since the “bugmeal” generated from its larvae and prepupae (the life stages of the fly before it becomes an adult) is nutritionally similar to fishmeal (Magalhães, 2017). Black soldier fly larvae (or BSF) carry the additional benefit of converting unwanted food waste into protein for fish feeds.
Prior studies looking into the effects of this insect protein showed that incorporating protein from BSF alongside fishmeal into high-protein diets resulted in similar growth to those only using fishmeal (Bondari & Sheppard, 1981). Knowing this, researchers at the Japan International Research Center for Agricultural Sciences experimented with using BSF as the sole source of protein into new, lower-protein diets. They tested whether this BSF diet could perform just as good as or even better than traditional fishmeal at growing fish.
It’s All in the Diet
To figure out how the BSF protein fares against fishmeal, researchers designed three different diet regimes for groups of growing fish: a 32% protein diet composed entirely of fishmeal, a 30% protein diet composed of a mix of BSF and fishmeal protein, and a 25% protein “fishmeal-free” diet, made entirely from black soldier fly larvae.
Once the diets were formulated, the researchers deployed nine cages (a total of three cages per diet plan) at the Living Aquatic Resources Research Center located in Vientiane, Laos. Each was filled with 200 young climbing perch (Anabas testudineus). Climbing perch were chosen since they are commonly farmed and are a staple food for the people of Southeast Asia. For 123 days, the researchers fed each group of growing fish on their special diets, recording their weights and length every 15 days to see how well the fish were growing. On the final day, the researchers selected 20 fish from each group, to analyze the body composition of each group.
More Than Meets the (Sock)Eye
The researchers found that there were no major differences in fish weight or length among the three groups. Additionally, there was no difference in the crude protein content of the fish, indicating the total amount of protein that the fish were able to convert into biomass. According to this, all three diets seemed to be equally good at growing the climbing perch.
Importantly, the 25% protein BSF diets showed no difference in growing perch to those fed the 32% protein fishmeal diets. This means that perch on the BSF diets had a higher protein retention rate. In other words, they were doing better at converting the insect protein into fish muscle.
The results of this study show that BSF can, in fact, be used as an alternative protein source for fish-diets. It can produce more efficient diets and reduce the dependency on fishmeal in the aquaculture industry. However, it should be noted that the results of this study are, so far, only true for the climbing perch. With more testing on the effects of a BSF diet in other species of fish, humanity may be on its way to replacing fishmeal altogether.
Péron G, Mittaine JF, Gallic BL. 2010. Where do fishmeal and fish oil products come from? An analysis of the conversion ratios in the global fishmeal industry. Marine Policy 34: 815–820. https://doi.org/10.1016/j.marpol.2010.01.027
Magalhães R, Sánchez-López A, Leal RS, Martínez-Llorens S, OlivaTeles A, Peres H. 2017. Black soldier fly (Hermetia illucens) pre-pupae meal as a fish meal replacement in diets for European seabass (Dicentrarchus labrax). Aquaculture 476: 79–85. https://doi.org/10.1016/j.aquaculture.2017.04.021
Bondari K, Sheppard DC. 1981. Soldier fly larvae as feed in commercial fish production. Aquaculture 24: 103–109. https://doi.org/10.1016/0044-8486(81)90047-8