UK - Overfishing has reduced fish populations and biodiversity across much of the world's oceans. In response, fisheries are increasingly reliant on a handful of highly valuable shellfish. However, new research by the University of York shows this approach to be extremely risky.
The research, published in the journal Fish and Fisheries, shows that traditional fisheries targeting large predators such as cod and haddock, have declined over the past hundred years. In their place, catches of shellfish such as prawns, scallops and lobsters have rocketed as they begin to thrive in unnaturally predator-low environments often degraded by the passage of trawls and dredges.
In many places, including the UK, shellfish are now the most valuable marine resource. The research by the Environment Department at York suggests that although a shellfish-dominated ecosystem appears beneficial from an economic perspective, it is highly risky.
Like simplified agricultural systems, these shellfisheries are unstable in the long-term and at great risk of collapse from disease, species invasions and climate change.
Lead author, Leigh Howarth, says: "Prawns are now the most valuable fishery in the UK, with catches currently worth over £110 million a year. But this fishery has come to exist only after we overexploited populations of cod, haddock and other predators. If shellfish now collapsed the social consequences for fishermen would be devastating. There are simply very few remaining species left to target."
The study reports similar findings from all over the world. In the United States and Canada, catches of lobster, scallops and crab have also come to dominate following the collapse of cod. However, disease and climate change again put these species at great risk.