Scientists at the Woods Hole Oceanographic Institution (WHOI) discovered that mid-sized fish, such as the bigscale pomfret, act as a crucial link between the deep ocean and surface food webs, explaining why large predators like sharks spend significant time in the ocean's twilight zone. The research, conducted in late December 2025, revealed that these fish reside in the mesopelagic zone during the day, a layer spanning 200 to 1,000 meters deep, and ascend at night to feed in shallower waters.

The study employed satellite tags to track the movements of these previously difficult-to-study fish. Danny Mears, a scientist involved in the project, explained that the tags allowed researchers to monitor the pomfret's behavior in unprecedented detail. The data collected indicated that the fish's vertical migration patterns are influenced by water clarity, potentially impacting the entire ocean food chain.

The mesopelagic zone, also known as the twilight zone, is a dimly lit region of the ocean where sunlight barely penetrates. It is home to a vast array of marine life, including many species of fish, squid, and crustaceans. These organisms play a vital role in the ocean's ecosystem by transferring energy from the surface to the deep sea.

According to WHOI, the bigscale pomfret's role as a link between the deep and surface food webs had been previously underestimated. By feeding in both zones, these fish facilitate the transfer of nutrients and energy, supporting a complex network of predators and prey. The researchers believe that changes in water clarity, potentially driven by climate change or pollution, could disrupt these migration patterns and have cascading effects on the entire ocean ecosystem.

The findings have significant implications for understanding the ocean's carbon cycle. The mesopelagic zone is a major reservoir of carbon, and the biological pump, driven by the movement of organisms like the bigscale pomfret, plays a crucial role in sequestering carbon from the atmosphere. Disruptions to this process could exacerbate climate change.

Future research will focus on further investigating the impact of environmental changes on the behavior of mid-sized fish and their role in the ocean's food web. Scientists plan to use advanced AI-powered models to analyze the vast amounts of data collected from satellite tags and other sensors. These models will help them predict how changes in water clarity, temperature, and other factors will affect the distribution and abundance of these important fish species. The research team also hopes to develop new technologies for monitoring the mesopelagic zone, including autonomous underwater vehicles equipped with advanced sensors and AI-driven data analysis capabilities.