UK waters may become more productive fishing grounds as climate change brings new species in from the south, according to researchers.
Fish such as red mullet, hake and sole have become more abundant in the last 30 years, as the waters have warmed.
But established favourites such as cod and haddock may be on the wane.
The findings come from an analysis of trawl data going back to 1980, covering about 100 million fish caught, and is published in Current Biology journal.
“This is the first attempt that’s brought together many different datasets,” said project leader Steve Simpson from Bristol University.
“People have been reluctant to piece together data from lots of different surveys because there are some tough challenges there.
“But we spent about a year doing it, and it really gives us the first comprehensive look at [the effects of climate change on] fish in European shelf waters.”
The relatively shallow waters of the European continental shelf include those around the UK and Ireland, spanning the North Sea, English Channel and Irish Sea.
Overall, three-quarters of the species in the area are responding to rising water temperatures, the team found.
And of those, three times as many are increasing in abundance as declining.
Previous studies have also indicated that species such as haddock and mackerel are moving northwards in response to warming – a situation that led to last year’s “mackerel war” between Iceland and the EU, with Scotland especially vociferous in protest against the Icelandic quota.
The team behind this study – drawn from eight UK research institutes and one in the Irish Republic – emphasises there is no guarantee that abundances of these species will continue to rise.
Each one needs not only water of a given temperature range but also factors such as a secure food supply and the right environment for reproduction.
Cod on hook Favourites such as cod may be harder to find
The impact of ocean acidification is also unknown, but unlikely to be beneficial given the evidence so far.
But if warming water is the main factor, the trends seen over last three decades are likely to continue, because further temperature increases are expected.
If they do, UK consumers could see a slowly rising abundance and diversity of seafood heading on their plates.
“The winners would include red mullet, grey gurnard, red gurnard, John Dory, lemon sole, dab, hake – these are all fish that you could at least ask your fishmonger to source for you,” Dr Simpson told BBC News.
“The losers would be haddock, pollock, whiting, cod – fish that evolved in cold conditions.”
The warm water species coming in are generally smaller, but grow and reproduce faster, which makes them relatively less prone to over-fishing than their cold-water counterparts.
Chasing crumbs from the table
The EU is engaged in a major overhaul of the Common Fisheries Policy (CFP), the mechanism that is designed to ensure sustainable fishing levels across European waters but which has signally failed to deliver on a number of counts.
Bertie Armstrong, chief executive of the Scottish Fishermen’s Federation (SFF), said the reformed CFP would have to take into account changes that were coming because of climate change.
“There’s a welcome [from us] to the scientific fact that there’ll be similar or better abundance – there are however some technical questions as to how, under climate change, these changed opportunities are distributed between nations,” he told BBC News.
Fishermen themselves would easily adapt to catching a slowly changing species mix, he said – but would consumers?
“Traditionally, the British consumer tends to like his fish in white slabs, preferably coated in breadcrumbs – that’s a huge, ridiculous over-generalisation, but there is a culture change that would be helpful to make best utilisation of what’s available and what’s going to be available.”
The team of scientists behind the Current Biology paper now intends to extend its research into warmer waters, analysing data from French, Italian and Spanish fleets that could shed light on changes in fishing grounds further south.
Whatever benefits warming waters might bring to UK fisheries, the worldwide impact of climate change is not forecast to be positive, with the overall productivity of oceans projected to decline.
This is likely to be abetted by ocean acidification, where increased carbon dioxide dissolves in seawater, meaning that organisms such as coral and mussels will find it progressively more difficult to form hard parts such as shells.
Author: Richard Black