Popular fish among the main engineers in seabed, shows research

Many fish that we eat play a key role in maintaining the seabed – and therefore our climate, according to new research. Scientists in the convex marine landscape survey evaluated the role of fish in bioturbation (barattage and sediment reworking) in the shallow seas of the United Kingdom. Their article, published in the journal Maritime environmental researchis entitled “a functional evaluation of fish as bioturbators and their vulnerability to local extinction”.

The Atlantic cod – an essential in restaurants – is at the top of the list of these important “ecosystem engineers” (as well as the Atlantic Hagfish and the European eel).

In total, 185 species of fish played a role in bioturbation – and 120 of them are targeted by commercial fishing.

“Oceanic sediments are the largest organic carbon reservoir in the world – so what is happening on the seabed in our climate,” said the PH.D. of the University of Exeter. The student Mara Fischer, who led the study.

“Bioturbation is very important for the way in which the seabed presents itself and stores organic carbon, so the process is essential to our understanding of how the ocean absorbs greenhouse gases to slow down the rate of climate change.

“Bioturbation is also important for wider and wider ocean ecosystems.

“We have a good understanding of how invertebrates contribute to global bioturbation, but so far, we lack half of history.

“Our study is the first to try to quantify the impact of fish bioturbation, and it shows that they play a significant and widespread role.”

Outsourced and neglected

The co-author, Professor Callum Roberts, of the Center for Ecology and Conservation of the Penryn Campus from Exeter in Cornwall, said: “We also found that species with the highest bioturbation impacts are among the most vulnerable to threats such as commercial fishing.

“Many of the largest and most powerful diggers and pretenders of sediments of the seabed, such as giant skates, the withdrawal and the cod, were so overexploited that they have almost disappeared from our seas.

“These losses are reflected in significant, but always uncertain changes, in the operation of the ecosystems of the seabed.”

The researchers examined the files of all the species of fish living on the continental plateau of the United Kingdom and found that more than half play a role in bioturbation – to assert and search the sediments during the nests of research of food, excavations and / or construction.

These different ways to rework the sediments – terminated bioturbation modes – alongside the size of the fish and the frequency of bioturbation, were used by researchers to calculate a bioturbation impact score for each species.

Examples include:

• European eel. Bioturbation mode: terror. Bioturbation score (out of 125): 100. IUCN conservation status: Danger criticizing. Pissed mainly using Fyke traps and nets, they are considered a delicacy in many parts of Europe and Asia – commonly prepared as smoked eel or dishes such as eel pie and eel soup. Threats include climate change, diseases and parasites, loss of housing, pollutants and fishing.
• COD of the Atlantic. Bioturbation mode: vertical excavator. Bioturbation score: 100. UICN status: vulnerable. Mainly caught using trawling and long line lines, they are consumed in many forms, including fish and fries, fresh nets, salted cod and cod liver oil. Threats include overfishing, climate change and habitat degradation. The populations have decreased in several parts of its range, in particular the North Sea and the west of the Atlantic.
• Common skate. Bioturbation mode: lateral excavator. Bioturbation score: 50. IUCN status: in danger criticize. Historically targeted by trawling and long lines, this species is now protected in several regions, but often accidentally captured (accessory sockets). Numbers have radically decreased due to overfishing. The species is vulnerable because of its large size, its slow growth rate and its low reproduction rate – only about 40 eggs are laid every two years, and each generation takes 11 years to reach maturity.
• Black sea. Bioturbation mode: Nest Builder. Bioturbation score: 36. UICN status: the least worrying. Mainly caught using lower trawling, Gillnets and Hook and Line. Fishing during the Frai season in April and May can have an impact on the replenishment of the population. Chaluling at the bottom at this time has the potential to eliminate fish, nests and eggs.
• Gurnard Rouge. Bioturbation mode: Sifter sediment. Bioturbation score: 16. IUCN status: the least worrying. Historically, no major interest in commercial fisheries, the species has been more targeted in recent years (including in Cornwall). It is mainly captured by trawlers. There is currently no management for no species of Gurnard in the EU: no minimum landing size, no quota – which could lead to unbearable fishing.

Julie Hawkins, another author of the study, said: “Whoever spent time underwater, whether diving in apnea or diving, knows that fish constantly dig up the seabed.

“It is difficult to believe that such obvious and important activity has been largely neglected when it comes to understanding the burial of the ocean.”

The Convex Seascape Survey is a partnership between Blue Marine Foundation, the University of Exeter and Convex Group Limited. The ambitious world research program over five years is the biggest attempt to date to build a better understanding of the properties and capacities of the ocean and its continental shelves in the carbon cycle of the earth, in an urgent effort to slow climate change.