A new study has found that commercial deep ocean fishing could have a catastrophic impact on bigeye tuna.
The species, which is one of the most valuable and widely consumed tunas, is heavily reliant on mesopelagic fish. These small species live in the deep ocean, and their harvesting by humans could deplete them to the point where the bigeye tuna populations are affected.
New proposals view mesopelagic fish, such as lanternfish and bristlemouths, as an excellent source of fishmeal and fish oil for aquaculture. However, careful management will be needed to avoid disrupting the delicate balance of the ocean.
Commenting on the findings, Ciara Willis, the study’s lead author who conducted the research as part of her PhD thesis in Biological Oceanography at the Woods Hole Oceanographic Institution, stated:
“Bigeye tuna rely heavily on mesopelagic fish for food, at a higher level and with greater consistency than previously assumed. If we remove too much of this critical food source via large-scale mesopelagic fisheries, we risk undermining existing tuna fisheries that support livelihoods around the world, and bigeye tuna won’t be the only species impacted. Numerous large marine predators from fish to whales to seabirds source a meaningful portion of their diets from the mesopelagic.”
Willis, who is now a postdoctoral fellow at the Monterey Bay Aquarium Research Institute, added:
“Mesopelagic fish are central to the ocean food web, and to the future of tuna fisheries. Decisions about deep-sea fisheries made today will shape ocean ecosystems for decades.”
While the study co-author, Melina Kourantidou, an environmental and resource economist and guest investigator at WHOI’s Marine Policy Center, added:
“From an economic perspective, this isn’t just a question of whether mesopelagic fishing is technically possible, but whether it makes sense once we account for what could be lost. If harvesting deep-sea forage fish undermines high-value fisheries like tuna, the total costs could far outweigh the benefits. Our results highlight the importance of considering these cross-fishery trade-offs before new fisheries expand.”
Finally, study co-author Di Jin, an expert in marine economics, contributed to the modeling approach that linked predator and prey added:
“Combining food-web science with economic modeling gave us a full picture of how coupled natural and human systems could respond to mesopelagic fishing.”
