Plastic-eating caterpillars

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Soon on the menu for salmon?

Waxworms fed on plastic waste have the potential to become a new source of protein for farmed salmon feed, researchers in Scotland say.

Waxworms, which are the caterpillar larvae of wax moths and are produced as a bait for angling, have been shown to readily consume polyethylene as part of their diet, making them potentially cheaper to produce.

Glasgow University-based start-up SalmoSim, which uses a salmon gut simulator that analyses the digestibility of alternative forms of aquafeeds, has found that waxworms fed on plastic waste offer the same nutritional value to farmed salmon as other commercially available insect meals.

Using the salmon gut simulator, the SalmoSim team tested the hypothesis that waxworms fed low-density polyethylene (LDPE) could be a more accessible source of protein for fish feeds, as well as solving a plastic waste problem. LDPE is not currently recycled and makes up around 20% of all waste.

Compared to other insect meals, and benchmarked against fishmeal, waxworms performed very well and could be an important source of feed for salmon, said SalmoSim in a press release. Further testing is now required to establish the safety of salmon fed on plastic-fed waxworms.

Martin Llewellyn, Professor of Molecular Ecology at Glasgow University and founding director of SalmoSim, said: “We are hugely encouraged by these data which indicate waxworms used to break down plastic could be a potential source of protein for farmed Atlantic salmon.

“As the pressure on wild fish stocks used for fishmeal continues to grow, the need to find alternative, sustainable and low-cost feed stocks for farmed fish has never been greater. While the next step is to ensure that plastic-fed wax worms pose no toxicity to salmon, and can safely enter the human food chain, there is clearly exciting potential here and we look forward to continuing with our research into sustainable protein sources for farmed Atlantic salmon.”

Llewellyn told Fish Farming Expert that he believes waxworms could eventually replace fishmeal, so long as pre-processing and amino acid content is suitable.

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Source: Fishfarmingexpert, 10 February 2023