Overfishing Threatens Fish Species That Are Key to Climate Stability and Seabed Health, Research Shows

Overfishing Threatens Fish Species That Are Key to Climate Stability and Seabed Health, Research Shows

(IN BRIEF) New research from the University of Exeter highlights the vital role of fish in bioturbation, the process of churning and reworking seabed sediments, which is crucial for maintaining healthy ecosystems and regulating climate change. The study found that 185 fish species contribute to bioturbation, with 120 of them targeted by commercial fishing. The research emphasizes the importance of preserving species like Atlantic cod, which play a significant role in sediment reworking. Overfishing of these species, including giant skates and halibut, could have uncertain but significant impacts on seabed ecosystems. The study is part of the Convex Seascape Survey, a global research initiative to better understand the ocean’s role in the carbon cycle.

(PRESS RELEASE) EXETER, 29-Apr-2025 — /EuropaWire/ — New research from the University of Exeter reveals that fish play a crucial role in maintaining the seabed, which is vital for climate regulation. The study, part of the Convex Seascape Survey, assesses the role of fish in bioturbation—an essential process that involves the churning and reworking of sediments in shallow UK seas. The research shows that many of the fish we rely on for food, including the Atlantic cod, are key “ecosystem engineers” in this process, with Atlantic cod sharing the top spot alongside the Atlantic hagfish and European eel.

In total, the study found that 185 fish species contribute to bioturbation, with 120 of these species being targeted by commercial fisheries. This highlights the significant impact of fishing on the seabed and its wider implications for the environment.

“Ocean sediments are the world’s largest reservoir of organic carbon, so what happens on the seabed is essential to our climate,” explained Mara Fischer, a PhD student at the University of Exeter and lead author of the study. “Bioturbation is crucial for how the seabed absorbs and stores organic carbon, which helps slow down climate change by reducing greenhouse gas emissions. This process is also vital for maintaining healthy seabed ecosystems.”

For the first time, the study attempts to quantify the role of fish in bioturbation. The research reveals that fish play a far more significant role in this process than previously understood, and their contribution is critical in maintaining the health of the ocean and its ecosystems.

Overfished Species:

Professor Callum Roberts, a co-author of the study from the University of Exeter’s Centre for Ecology and Conservation, added: “Many of the fish species with the highest bioturbation impacts, such as giant skates, halibut, and cod, have been severely overfished and are now at risk of disappearing from our seas. The loss of these species could lead to significant, though still uncertain, changes in the way seabed ecosystems function.”

The researchers examined fish species living on the UK continental shelf and found that more than half play a role in bioturbation through activities such as sifting and excavating sediment during foraging, burrowing, and nest building. The researchers calculated a “bioturbation impact score” for each species based on their size, frequency of bioturbation, and the way they interact with the seabed.

Key Findings:

• European eel: Bioturbation mode: burrower. Bioturbation score: 100. IUCN status: critically endangered.
• Atlantic cod: Bioturbation mode: vertical excavator. Bioturbation score: 100. IUCN status: vulnerable.
• Common skate: Bioturbation mode: lateral excavator. Bioturbation score: 50. IUCN status: critically endangered.
• Black seabream: Bioturbation mode: nest builder. Bioturbation score: 36. IUCN status: least concern.
• Red gurnard: Bioturbation mode: sediment sifter. Bioturbation score: 16. IUCN status: least concern.

Dr. Julie Hawkins, another author of the study, commented: “Anyone who has spent time underwater, whether snorkeling or diving, knows that fish are constantly digging up the seabed. It’s surprising that such an obvious and essential activity has been largely overlooked when understanding ocean carbon burial.”

The Convex Seascape Survey, a partnership between the Blue Marine Foundation, the University of Exeter, and Convex Group Limited, aims to better understand the role of the ocean and its continental shelves in the global carbon cycle. This research is part of a five-year global project focused on slowing climate change.

The findings of the study, titled “A Functional Assessment of Fish as Bioturbators and Their Vulnerability to Local Extinction,” were published in Marine Environmental Research.

Media Contact:

email: pressoffice@exeter.ac.uk

SOURCE: University of Exeter