Large marine predators, including great white sharks, have been found to explore the ocean’s twilight and midnight zones, according to a new study conducted by researchers. The study, which analyzed data from 12 species of large predatory fish, revealed that these predators frequently visit the mesopelagic zone, also known as the twilight zone, and the midnight zone, both located far beneath the depths at which they typically feed.
The mesopelagic zone is situated between depths of 656 and 3,280 feet, while the midnight zone extends from 3,280 to 9,800 feet below the ocean surface. By matching the diving patterns of 344 electronically tagged predatory fish with shipboard sonar, the researchers were able to identify the species that regularly venture into these deeper zones.
One significant finding of the study was the correlation between the dives of these predators and the presence of the deep scattering layer (DSL). The DSL is a densely packed layer of small fish and marine organisms. The research suggests that these marine predators feed on animals within the DSL. However, many of them dive even deeper than the DSL itself, for reasons that remain unknown.
The fact that large marine predators spend time in the twilight and midnight zones reveals that these zones are crucial habitats that have not received adequate attention. This is particularly concerning as several commercially fished species inhabit these zones. Therefore, understanding and protecting this potentially significant ecosystem is of paramount importance.
The study’s findings also raise questions about the potential exploitation of the mesopelagic zone’s biomass. If there is indeed more biomass in the twilight zone than in all current marine capture fisheries combined, there could be a “mesopelagic gold rush” to capture and utilize this resource. However, sustainable harvesting cannot take place without further research on the links between predators and mesopelagic biomass.
The researchers highlight the need for continued study and conservation efforts to preserve these critical habitats and ensure the long-term sustainability of marine ecosystems. This study serves as a reminder that there is still much to discover in the depths of the ocean and underscores the urgency to protect these fragile ecosystems for future generations.
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