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 extending from 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 hard-to-study fish. Danny Mears, a researcher involved in the project, explained that the tags provided unprecedented insight into the fish's daily vertical migrations. "We were able to observe, for the first time, how these mid-sized fish connect the deep and surface ecosystems," Mears stated.

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, but its role in the larger ocean ecosystem has been relatively unknown. This research highlights the importance of these mid-sized fish in transferring energy and nutrients from the deep ocean to surface waters, sustaining larger predators.

The researchers also found that the fish's movements are influenced by water clarity. Changes in water clarity, potentially caused by climate change or pollution, could alter the fish's behavior and disrupt entire ocean food chains. This finding underscores the vulnerability of deep-sea ecosystems to environmental changes.

The implications of this research extend beyond the scientific community. Understanding the intricate connections within ocean food webs is crucial for effective fisheries management and conservation efforts. By identifying key species, such as the bigscale pomfret, scientists can better predict how changes in the environment will impact marine ecosystems and develop strategies to mitigate those impacts.

Future research will focus on further exploring the role of mid-sized fish in the ocean's carbon cycle. These fish consume organic matter in the surface waters and transport it to the deep ocean, effectively sequestering carbon. Understanding the efficiency of this process is essential for predicting the ocean's capacity to absorb carbon dioxide from the atmosphere and mitigate climate change.