Baby fish prefer plastic over natural food

London: Young fish exposed to micro plastic particles during development tend to eat plastic and ignore their natural food source of free-swimming zooplankton, a new study has found.

Researchers from Uppsala University in Sweden found that larval perch exposed to microplastic particles show changed behaviours and stunted growth which lead to greatly increased mortality rates.

Microplastic particles (less than 5mm in size) originate from large plastic waste products that fragment into smaller pieces, or from manufactured plastics of microscopic size (eg, microbeads in personal care products).

These microscopic waste particles reach oceans via waterways and lakes and accumulate in high concentrations in
shallow coastal areas.

For the first time, scientists have been able to show that development of fish is threatened by microplastic pollution.

"Fish reared in different concentrations of microplastic particles have reduced hatching rates and display abnormal behaviours," said Oona Lonnstedt from Uppsala University.

"The microplastic particle levels tested in the current study are similar to what is found in many coastal habitats in Sweden and elsewhere in the world today," said Lonnstedt.

Larval perch exposed to environmentally relevant concentrations of microplastic polystyrene particles displayed stunted growth rates.

Researchers found that this was related to larval feeding preferences as perch that had access to microplastic particles only ate plastic and ignored their natural food source of free-swimming zooplankton.

"This is the first time an animal has been found to preferentially feed on plastic particles and is cause for concern," said Peter Eklov, professor at Uppsala University.

"Larvae exposed to microplastic particles during development also displayed changed behaviours and were much less active than fish that had been reared in water that contained no microplastic particles," said Lonnstedt.

"Furthermore, fish exposed to microplastic particles ignored the smell of predators which usually evoke innate antipredator behaviours in naive fish," said Lonnstedt.

The lack of an antipredator response made larvae more vulnerable to predators.
When perch were placed together with a natural predator (pike), fish that had been exposed to microplastic particles were caught and eaten more than four times quicker than control fish, with all fish exposed to microplastic particles dead within 48 hours.

If this response in fish larvae translates to higher mortality rates as a result of increased predation risk in nature, there could be direct consequences for the replenishment and the sustainability of fish populations.

The study was published in the journal Science.