If in the Mediterranean it is the brown shrimp that causes headaches for fishermen and environmentalists, in the surroundings of the Strait of Gibraltar there is another invasive species that is causing havoc, the Asian algae Rugulopteryx okamurae. Thus, in a matter of a few months it was able to cover more than 90% of some seabeds. But a research team from the University of Malaga has turned the story around: they now know what to do with the more than 60,000 tons of that algae that predictably They will arrive this year on the Andalusian coast: fish food. A very good one.
The discovery. The team fed mullet for 66 days with a diet composed of a feed containing treated algae. The resulting fish had more protein, less fat and more omega-3 in its meat, in addition to improving the intestinal microbiota that helped them better process other nutrients and improved their immune system. Spoiler: the algae in its natural state is toxic to fish.
Why is it important. On the one hand, because it is a way to dispose of the thousands of tons of algae that collapse the beaches and seabeds of southern Spain every year, within a circular economy model that reduces dependence on fishmeal and fish oils, two common ingredients in the manufacture of feed. On the other hand, the fish obtained is nutritionally more attractive for consumption, although this study does not evaluate its effect on humans, it only focuses on the muscle of the fish.
The algae plague. Rugulopteryx okamurae It is a brown algae native to the northwest Pacific that lives on rocky bottoms, generally between 0.5 and 35 meters deep (although it has been detected up to 40 meters in the Bay of Ceuta). Its arrival in the Mediterranean dates back to 2002, when was accidentally introduced next to Japanese oysters in the French Thau lagoon.
In Spain was detected for the first time on the coasts of Ceuta in 2015 and just a year later, it had already devastated the rocky bottoms. Since then, this algae has colonized a good part of the coast of Cádiz and Málaga, displacing native flora and generating accumulations of biomass that force city councils to allocate budget items to its cleaning.
In detail. To go from an algae that is toxic to fish to turning it into such a potentially interesting ingredient for feed, the team carried out an enzymatic hydrolysis and microbial fermentation treatment, thus eliminating its natural chemical compounds that the algae uses to defend itself and thus enable its digestibility. For the feed, they tested two concentrations, 5 and 15%: the first was more effective in improving the protein and omega-3 profile, while the second also reduced fat, but activated markers related to immunity and oxidative stress.
Yes, but. This is a study that has been carried out with commercial-sized fish, so growth parameters, feed conversion or digestibility were not measured, something essential to know if this way of recycling algae is economically viable. Furthermore, the long-term health of the fish was not evaluated either; 66 days is too short a period of time. On the other hand, a single study with only one species of fish and that period is not enough to think about marketing a feed. In addition, this algae naturally accumulates heavy metals, something that also needs to be explored further.
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Cover | Mariajoao22 and Mar Menor Canal
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