A fifth of male fish in UK rivers now ‘trans-gender’ due to chemicals in human waste

Research by Professor Charles Tyler, a leading fish physiologist and eco-toxicologist from the University of Exeter, has shown male fresh-water fish are displaying ‘feminised’ traits, demonstrating ‘female’ behaviour and even producing eggs.

The chemicals causing these effects are flushed down the loo and include ingredients in the contraceptive pill, and by-products of cleaning agents, plastics, and cosmetics.

Professor Tyler will present his findings in the opening lecture of the 50th Anniversary Symposium of the Fisheries Society in the British Isles, held in Exeter University 3-7 July 2017.

The week-long symposium will include papers from international experts on fish physiology and behaviour, and discuss the threats fish populations face from over fishing, climate change and human pollution.

Professor Tyler’s lecture the Feminisation of Nature – an Unnatural History is the keynote speech at the international symposium on Monday 3 July.

The Exeter University scientist will explain how 20 per cent of male fresh-water fish, such as roach, tested at 50 sites, had feminine characteristics.

Some male fish have reduced sperm quality and display less aggressive and competitive behaviour, usually associated with attracting females of the species, which makes them less likely to breed successfully.

Professor Charles Tyler, in his keynote lecture on the impact of chemicals on fish, will also explain that the offspring and grandchildren of transgendered fish can be more sensitised to the effects of those chemicals in subsequent exposures.

Over 200 chemicals from sewage plants have been identified with oestrogen-like effects. Some not only are creating ‘trans-gender’ fish but effecting fish physiology in surprising ways.

Drugs such as anti-depressants are also altering fish’s natural behaviour.

“We are showing that some of these chemicals can have much wider health effects on fish that we expected. Using specially created transgenic fish that allow us to see responses to these chemicals in the bodies of fish in real time for example we have shown that oestrogens found in some plastics affect the valves in the heart, “ Professor Tyler said.

He added: “Other research has shown that many other chemicals that are discharged through sewage treatment works can affect fish including antidepressant drugs that reduce the natural shyness of some fish species, including the way they react to predators.”

The symposium will include papers from international experts on fish physiology and behaviour, and discuss the threats fish populations face from over fishing, climate change and human pollution. Representatives of the fishing industry will also attend.

The Symposium at Exeter University includes dozens of lectures and presentations of research including:

• Fish biodiversity defrosted: unveiling non-compliant seafood trade in British ethnic food
• Losing Nemo: how the destruction of coral reefs and their distinctive sounds means fish are getting lost and cannot find their way home
• How fish are shrinking in size due to climate change
• How coral reef fish use alarm calls to signal to one another
• The impact of man-made noise on fish
• The electromagnetic world of fish: how power cables can disrupt how fish look for food and sexual partners
• Archaeological fish data and how it can be used
• Impact of flame retardants on fish
• How stress can affect the welfare of popular ornamental fish
• Return of the apex predator, the Atlantic Bluefin tuna, to British coastal waters
• The impact of ocean warming on the behaviour of sharks
• How the use of mosquito nets by fishermen is killing fish they do not mean to catch
• Using genes to identify where fish have been during their lives

The symposium, organised by Dr Steve Simpson, a leading expert on fisheries, climate change, bioacoustics and marine noise pollution, will include 7 plenary lectures and more than 200 talks from delegates representing 28 countries.

Dr Simpson of the University of Exeter, concludes: “This will be an exciting week of talks, posters, discussions and social events. But it also gives fish biologists from around the world a chance to exchange ideas and discuss how to protect dwindling fish populations in rapidly changing seas and rivers, before it is too late.”