An interview with Itay Oz, Robert H. Smith Faculty of Agriculture, Food, and Environment, The Hebrew University of Jerusalem.
*We would like to thank Prof. Lior David for his valuable contributions.
Q: Can you provide an overview of the Grey Mullet All-Female Project?
Itay Oz: The project, under the supervision of Prof. Lior David from the Robert H. Smith Faculty of Agriculture, aims to produce an all-female grey mullet population by establishing a broodstock of regular females and sex-reversed males. The project began with a collaboration between Dagon, Prof. Lior David, and the Fisheries Research Station at Dor (part of the Ministry of Agriculture and Food Security). To date, this project is administered by Dagon and Lior David's Lab.
Q: Could you describe the biological mechanism underlying this process?
Itay Oz: In grey mullet fish, sex determination follows an XX/XY system, where males are XY and females are XX, meaning the male is responsible for determining the sex of the offspring. This is distinct from species with WZ/ZZ systems, such as birds and some fish species, where the female determines the offspring's sex. Establishing that the grey mullet is an XY species was a crucial first step in our research. Secondly, to obtain sex-reversed males (XX males), this natural genetic mechanism of sex determination had to be overruled by the administration of a masculinizing hormone to normal groups containing both XX and XY progeny. This hormonal manipulation drove the development of testes in XX progeny. Thirdly, based on mapping of the gene that naturally determines sex, a set of genetic markers was developed, allowing screening of hormonally manipulated progeny to identify XX males. Understanding all these allowed us to design our approach for creating an all-female population.
Q: What are the primary markets for this project, and what potential do they hold?
Itay Oz: Female grey mullets grow faster and larger than males, making them more profitable for aquaculture. Further, since females have a faster growth rate than males, growing only females yields more uniform sizes at harvest. Additionally, females produce eggs that are used to make Karasumi and Bottarga, high-value delicacies in Mediterranean, Japanese, Taiwanese, and Korean cuisines. Since the sex of fish is indistinguishable until maturation, growing fish for the production of these delicacies entails growing males as well, which is inefficient. This dual market potential for meat and egg products significantly enhances the economic potential of the project.
Q: Can you outline the main stages and objectives of the project?
Itay Oz: The project's main goal is to produce grey mullet meat and egg products. Female grey mullets develop gonads and hatch only in seawater, although they are nursed and fattened in freshwater ponds. Our strategy involves creating genetically female mullets with male phenotypes as brood fish. When these males breed, their offspring are all-female XX. Initially, we fed the grey mullet broodstock with feed coated in different dosages of testosterone. Timing the hormone treatment to coincide with the fish's sex differentiation was critical. At maturation, we examined approximately 100 fish to identify gonad types, expecting over 50% to exhibit male characteristics as a preliminary success indicator. During breeding, males produce sperm early, while females are identified by their abdominal gonads. We separated females and genotyped the males, removing those with XY genotypes. The remaining males, which were XX, received hormonal boosts to facilitate sperm production. Our first successful hatch yielded 300ml of all-female eggs.
Q: Where does the project stand today at the Dagon and Dor research centers, and what are the next steps for the Volcani Institute?
Itay Oz: Currently, we have as brood fish a few males with female genotypes. Another fingerling group is undergoing testosterone feeding to produce more. With these males, we started producing all-female seeds alongside our production of regular mixed progeny groups. Our main barrier now is obtaining more male phenotype females to establish larger broodstock. Our future research will focus on breeding during the next natural hatching season to create all-female groups and test their growth to establish their advantages.
Q: Can you share a bit about your academic background?
Itay Oz: I graduated from the Ruppin Academic Center with a BSc in Marine Sciences and earned a master's degree in Neurobiology from Tel Aviv University. I am currently pursuing a PhD at the Volcani Institute and Robert H. Smith Faculty of Agriculture, Food, and Environment under the supervision of Dr. Matan Golan and Prof. Lior David, focusing on the molecular and morphological characterization of grey mullet larval development and metamorphosis.
#Aquaculture #GreyMullet #AllFemaleProject #AquacultureInnovation #MarineBiology #SustainableFarming #AquacultureResearch #FisheriesResearch #AquacultureTechnology #AquacultureDevelopment #MarineSciences #AquacultureIndustry #FishFarming #AquacultureGrowth #SustainableSeafood #AquacultureMarkets #ResearchAndDevelopment #AquacultureFuture #AquacultureScience #AquacultureEconomics #MarineEcosystems #AquacultureProduction #SustainableFishFarming @The Hebrew University Of Jerusalem @Itay Oz @Lior David
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