What critical, energy-draining parental sacrifice is made by the male arowana during the incubation period for young fish?

The male parent holds the fertilized eggs in its mouth for incubation, often fasting for the entire two-month duration

Both Silver Arowanas and Asian Arowanas share a specialized reproductive strategy known as mouthbrooding. In this process, the responsibility for protecting the developing embryos falls primarily on the male parent. After fertilization, the male takes hundreds of eggs into his mouth, where they remain protected from predators and environmental risks until they hatch and the fry are developed enough to swim independently. This act of carrying the developing brood is energetically costly because the male must refrain from eating throughout the entire incubation period, which can last as long as two months. During this extended time, the male fasts completely while providing a safe nursery within his oral cavity for the offspring.