Rising human exploitation of little fish — including anchovy, sardine, herring, mackerel and capelin — had had far less attention in marine research compared to big commercial species such as cod, tuna, swordfish or salmon, they said.
Over-fishing of small fish has “significant effects on other parts of the marine ecosystems,” said Tony Smith, the lead author of the study at the Commonwealth Scientific and Industrial Research Organization in Australia.
He said that the findings, published in the journal Science, were the first comprehensive analysis of how catching small fish, as well as shrimp-like krill, can disrupt marine food chains and so affect human food supplies.
Little fish play a pivotal role since they mainly eat tiny plankton and are in turn food for predators such as large fish, whales or seabirds. Small fish account for more than 30 percent of world fish production and are a key food source for many people in developing nations.
The scientists, who used computer models to study stocks of small fish off Peru, the California current, southern Africa, the North Sea and Australia, suggested that catches of should be cut sharply, perhaps backed up by no-fishing zones.
They said some stocks were harmed even by a level of catches known as the “maximum sustainable yield” (MSY) of a stock.
“Halving exploitation rates would result in much lower impacts on marine ecosystems, while still achieving 80 percent of MSY,” the study said.
FISHMEAL
Smith told Reuters said that lower fishing rates would probably bring long-term economic benefits, as well as helping recovery of other, larger species that have been in decline due to over-fishing.
Smith and other experts in the United States, Britain, South Africa, France, Peru and Australia said that small fish — were often ground up into fishmeal as feed for livestock or for farmed fish. About 10 to 20 percent were consumed by people.
Big catches of small fish often had damaging effects even though it might benefited other creatures lower down the food web, such as plankton, jellyfish or squid.
It said that a complicating factor was that there were often big natural variations in fish stocks, such as in numbers of anchovies or sardines off Mexico.
