Israeli Innovation Could Feed World With Bigger, Farmed Fish

Prevented from reproducing, fish grow a lot bigger, Jerusalem professor proves on tilapia

Ruth Schuster
Ruth Schuster
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A not particularly large tilapia from the Sea of Galilee. It probably spent its energy reproducing rather than growing. Picture shows the torso and arms of a man wearing a gray T-shirt, holding in wet, dirty hands what is probably a dead tilapia, about double the size of his palm.
A not particularly large tilapia from the Sea of Galilee.Credit: Gil Eliahu
Ruth Schuster
Ruth Schuster

The world population is projected to approach 10 billion by the year 2050, and with climate change roaring, how are they to be fed? An Israeli professor has won an award for her discovery on how to make fish grow bigger with the same inputs, theoretically rendering fish farming a lot more productive.

We already have 7.5 billion people on the planet and food insecurity is not just a figment of war: Africa, Asia and South America have large populations suffering from malnourishment. Wild fish, a food resource since time immemorial, have been decimated by overfishing, pollution, and climate change, which has myriad effects on seawater quality beyond its temperature. Other species, from seals to polar bears to African penguins, have also been devastated as man clears the seas of edible life.

Fish farming is no panacea, either for world starvation or the ecology. The sins of fish farmers against the habitat may range from fouling the local waters with concentrated fish waste and nutrients, to concentrating parasites that infect wild fish. Salmon farming, in cages in the open sea, has come under attack in particular, not least for infecting wild brethren with sea lice. So if we're going to farm our fishy friends, at least let's do it efficiently.

Key to the innovation is that reproduction in fish is enormously energy-intensive. This has been known. It has also been generally supposed that if their reproduction is prevented, delayed or somehow thwarted, they won't start swimming marathons, but will divert that energy into growth.

Now zoologist and aquaculturist Prof. Berta Levavi-Sivan at the Hebrew University of Jerusalem has identified two tiny proteins called neurokinins (peptide chains that have neurological activity), fondly named Neurokinin B (NKB) and Neurokinin F (NKF), that play a crucial role in promoting piscine reproduction. Both are secreted in the brain.

She and the team developed molecules to disrupt reproduction in fish by neutralizing NKB and NKF. These new molecules did inhibit fish reproduction – and did lead to increased growth rates. QED.

"If we delay reproduction a little, the fish will grow more," Levavi-Sivan told Haaretz. "Fish invest in making millions of eggs, so they invest a great deal of energy in preparing the gonads for reproduction. Once that is disrupted, the energy will go towards growth."

So far they have proved the theory in tilapia, a toothsome fish locally called moosht, amnun or St. Peter's Fish, found in the Sea of Galilee.

Young tilapia fed the neurokinin inhibitors in their food for two months gained 25% more weight compared with fish that did not receive the supplement, she says (unpublished).

"We found NKB in every fish we tested," Levavi-Sivan confirmed to Haaretz, and is willing to speculate that it exists in every fish, period. Ergo, the invention of the antagonists to the neurokinins could theoretically work with every farmed fish.

(The Sea of Galilee tilapia were also famous for their massive die-off in 2015, from a mysterious disease that turned out to be a previously unknown virus.)

The chemical can be put in the fish food, which would be precluded from reaching wild fish around the fish farm because the systems are usually closed, Sivan explains. At this point the team is working on characterizing the molecules they invented. In recognition of her work, Prof. Levavi-Sivan was awarded the Kaye Innovation Award for 2017, a the Hebrew University prize established in 1994 to encourage faculty, staff and students of the Hebrew University to develop commercializable innovative methods and inventions.

Meanwhile, the technology developed by Prof. Levavi-Sivan and her team was licensed by Yissum, the Technology Transfer company of the Hebrew University, to a startup named AquiNovo, which is run in the Trendlines venture group.

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