A school of Jack Mackerel (Trachurus declivis). (Photo: Graham Blight, CSIRO)
Experts urge drop in small fish harvesting
Monday, July 25, 2011, 02:30 (GMT + 9)
The harvesting of small fish needs to be drastically reduced and monitored to protect the marine food chains. The fishing cuts should even be buttressed by no-fishing zones, according to an international team of experts underscored in the journal Science.
Even purportedly sustainable fishing levels of these fish are harmful to marine ecosystems and species higher up in the food chain, the researchers concluded.
The experts determined that overfishing of small species has "significant effects on other parts of the marine ecosystems," explained Tony Smith, the lead author of the study at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia.
He said the findings comprise the first wide-ranging analysis of how catching small fish and krill can interfere with marine food chains and ultimately trim down human food supplies, Reuters reports.
Because little fish eat mostly tiny plankton and are prey for large fish, whales or seabirds, small species play a crucial role. They make up more than 30 per cent of world fish production and many people in developing nations rely on them as a staple food source.
|Dr Tony Smith AM. (Photo: CSIRO)
The scientists used computer models to study populations of small fish off Peru, the California current, southern Africa, the North Sea and Australia.
They believe catches need to drop sharply if these stocks are to be saved, as some were harmed even by the maximum sustainable yield (MSY) of a stock.
"Halving exploitation rates would result in much lower impacts on marine ecosystems, while still achieving 80 per cent of MSY," the authors wrote.
Curbing fishing rates may offer long-term economic benefits and also help other, larger species recuperate from overfishing, Smith said.
He and other experts in the US, Britain, South Africa, France, Peru and Australia noted that small fish are often ground up into fishmeal and used as feed for livestock or farmed fish. Only around 10-20 per cent of small fish are actually reserved for human consumption.
Even though diminishing numbers of small fish may benefit other animals lower down the food web, such as plankton, jellyfish or squid, damaging effects remain.
The researchers pointed out that a complicating factor in play is the trend of significant natural variations in fish stocks, such as in numbers of anchovies or sardines off the Mexican coast.
For example, fishing anchovies off Australia’s southeastern coast has much less of an impact on the local ecosystem than harvesting them off the Californian coast. The impacts were worst when these species make up a “high proportion of the biomass in the ecosystem or are highly connected in the food web,” PhysOrg.com reports.
The study was initiated and largely funded by the Marine Stewardship Council (MSC) with the goal of ensuring its guidance to certifiers on assessing low trophic level fisheries so that they meet global best practice.
- Overfishing of big species leaves more small fish in the sea: study
By Natalia Real