The fish that is getting smaller to slip through nets
The average size of eastern Baltic cod is shrinking as a result of overfishing, scientists have claimed.
The fish are thought to have evolved to slip through nets, according to a study which directly links human influence to changes in their DNA.
The research, published in the Science Advances journal, also blamed decades of overfishing for the dwindling numbers of the species.
'When the largest individuals are consistently removed from the population over many years, smaller, faster-maturing fish gain an evolutionary advantage,' said Prof Thorsten Reusch, senior author of the study and head of the marine ecology research division at Geomar Helmholtz Centre for Ocean Research Kiel.
'What we are observing is evolution in action, driven by human activity. This is scientifically fascinating, but ecologically deeply concerning.'
Researchers examined tiny ear bones, called otoliths, of 152 cod caught in the Baltic Sea's Bornholm Basin between 1996 and 2019.
The otoliths record annual growth, similar to tree rings, and showed the genomes of fast-growing cod had nearly disappeared, while slower-growing, smaller fish had a higher survival rate.
Overall, the average body length of the fish had roughly halved from 40cm to around 20cm since the 1990s.
Dr Kwi Young Han, a biologist and first author of the study, said: 'For the first time in a fully marine species, we have provided evidence of evolutionary changes in the genomes of a fish population subjected to intense exploitation, which has pushed the population to the brink of collapse.'
The EU banned the fishing of eastern Baltic cod in 2019 following years of period of overfishing. However, scientists warned its population may never fully recover.
Prof Reusch said: 'Evolutionary change unfolds over many generations. Recovery takes far longer than decline, and it may not even be possible… despite the fishing ban, there's no sign of a rebound in body size.'
Dr Han added: 'Our results demonstrate the profound impact of human activities on wild populations, even at the level of their DNA.
'They also highlight that sustainable fisheries are not only an economic issue, but also a matter of conserving biodiversity, including genetic resources.'
Hashtags
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
BBC News
13 hours ago
- BBC News
Shoots of hope for Britain's cherished ash trees
Ash trees are fighting back against a disease that has ravaged the British countryside, new scientific evidence ash dieback arrived in 2012, predictions suggested up to 85% of ash trees could be now scientists have discovered that ash woodlands are naturally evolving greater resistance to the discovery offers renewed hope that the much-loved trees will survive in the British landscape. "It is hope born out of the death of a lot of trees," said Prof Richard Buggs of the Royal Botanic Gardens Kew, and Queen Mary University of he said other interventions would be needed to give ash trees a helping hand, such as protecting trees from grazing deer and breeding the most resilient trees for future planting schemes."We have fresh motivation to look after our ash populations, to protect them from other problems like deer browsing, and to let nature take its course and evolve trees with more resistance," he told BBC Ash dieback fungus originated in Asia and was introduced to Europe about 30 years study of ash trees at a woodland in Surrey revealed subtle shifts over time in different genes, which should help new saplings fight back against trees are evolving greater resistance to the disease than their predecessors - an example of Charles Darwin's natural selection theory in Nichols, professor of evolutionary genetics at Queen Mary University of London, said a "tragedy for the trees has been a revelation for scientists: allowing us to show that thousands of genes are contributing to the ash trees' fightback against the fungus". Ash dieback demonstrates how devastating introduced pathogens can be for our trees and the species which rely upon them, said Rebecca Gosling of the Woodland Trust. "The findings highlight how vital it is to support natural regeneration in woodlands, furthering our understanding of how to best manage our ash woodlands," she had feared the ash would go the way of the elm, which has been almost wiped out by Dutch elm loss of the native tree would have a devastating effect on biodiversity as well as changing the face of the landscape. Since its arrival in Britain in 2012, ash dieback has spread to every corner of the British Isles, causing widespread damage to fungus genetic code unravelledAlarm call as world's trees slide towards extinctionAsh tree set for extinction in EuropeSigns of the disease can be seen through withered and blighted many cases the fungal disease will eventually kill the research is published in the journal, Science.
Times
13 hours ago
- Times
Ash trees evolving resistance to dieback
The forces of evolution are helping Britain's ash trees to fight back against a deadly fungus that has threatened to decimate the species, a study suggests. After ash dieback was first recorded in the UK in 2012 experts warned that the disease had the potential to 'change the landscape for ever' by killing up to 90 per cent of Britain's 150 million ash trees, which in 2019 accounted for about 12 per cent of the nation's broadleaf woodland. However, analysis suggests that natural selection — the evolutionary process first described by Charles Darwin — is already favouring traits that will help young ash survive. Ash trees were felled in places such as Lower Woods, Gloucestershire, to limit the spread of dieback ALAMY Scientists from the Royal Botanic Gardens, Kew, and Queen Mary University of London compared older trees with new saplings. They found thousands of genetic differences that appeared to be allowing younger trees to withstand the fungus more successfully than their predecessors. Professor Richard Buggs, a senior scientist at Kew and co-author of the study, said the research had raised hopes that ash could fare better than Britain's elms, which were all but wiped out by Dutch elm disease. 'These findings suggest that ash will not go the way of the elm in Britain,' Buggs said. 'Elm trees have struggled to evolve to Dutch elm disease [because of low levels of genetic diversity] but ash are showing a very different dynamic because they produce an abundance of [genetically different] seedlings upon which natural selection can act when they are still young.' Ash dieback causes leaf loss and stem lesions and often results in trees dying. The research team analysed trees in Marden Park wood in Surrey, a site managed by the Woodland Trust. By studying thousands of variants of different genes, they identified subtle changes between generations. Charles Darwin's theory of evolution proposes individuals within a species most suited to their environment will survive and pass on those benefits to their offspring ALAMY 'A tragedy for the trees has been a revelation for scientists, allowing us to show that thousands of genes are contributing to the ash trees' fightback against the fungus,' said Professor Richard Nichols, an evolutionary geneticist at Queen Mary University London. Even so, the researchers warned that the future of the species in Britain was not guaranteed. 'Natural selection alone may not be enough to produce fully resistant trees. The existing genetic variation in the ash population may be too low and, as the trees become scarcer, the rate of selection could slow,' said Dr Carey Metheringham, an author of the study, which has been published in the journal Science. 'Human intervention, such as selective breeding and the protection of young trees from deer grazing, may be required to accelerate evolutionary change,' Metherington added.
The Independent
16 hours ago
- The Independent
What over-fishing has done to the size of cod in just 30 years
Excessive fishing has caused Baltic cod to undergo genetic changes, halving their size over the past 30 years. A study published in Science Advances is the first to demonstrate that decades of overfishing and environmental changes can profoundly alter the genetic makeup of a fully marine species. Researchers found a 48 per cent decrease in the asymptotic body length of Eastern Baltic cod between 1996 and 2019, with genetic variations indicating evolution driven by human interference. The study revealed that the genomes of fast-growing cod systematically differed from slow growers, with fast-growing individuals nearly disappearing from the Baltic Sea. This phenomenon is described as evolution in action driven by human activity, where the consistent removal of larger fish gives smaller, faster-maturing fish an evolutionary advantage.
