Biologist Beatriz Diaz Pauli catching guppies. (Photo: Kim E. Andreassen,uib.no)
Novel experiment investigates overfishing's effects on fish development
Tuesday, September 20, 2011, 23:40 (GMT + 9)
Does overfishing change the behaviour and development pattern of fish? Scientists are trying to find out.
Researchers have already established that overfishing selects for smaller fish. Now, a team of scientists will take away the largest fish from populations of lab-raised guppies to investigate the impact, wrote BBC News’s science reporter Jennifer Carpenter.
The team is now reporting at the meeting of the European Society for Evolutionary Biology in Germany.
"There are clear indications that almost all... commercial fish are shrinking," commented marine biologist Carl Lundin, who directs the International Union for the Conservation of Nature's (IUCN) Global Marine and Polar Programme.
Both stocks and the fishing industry benefit from larger fish: for mass spawning species such as cod, older larger females are beneficial, as they are the best at replenishing the population. And larger fish, Lundin said, are advantageous for fishers.
In addition, industrial fishing may have another effect: earlier reproduction in fish.
|Male guppy. (Photo: EvoFish)
To investigate additional upcoming changes in marine life, evolutionary biologist Beatriz Diaz Pauli and her team from the University of Norway have established nine populations of guppies of 500 to 900 individuals each.
In the next few years, Diaz will remove all the fish longer than 16mm from three of the tanks. In the rest, she will eliminate those shorter than 16mm or randomly, which will serve as a control for what results from altering the density of fish in the tanks.
Shifts in the fish's growth rate, age and size of maturation, reproductive effort and mating and feeding behaviours will be documented.
The goal is to discern if the changes result from fish adapting to a new environment, called a plastic response, or from genetic changes.
It is of note that plastic responses are not inherited.
While a fish might grow smaller if fed little food as a juvenile (a plastic response), its young would be able to grow large if fed sufficiently. But genetic responses are inherited, such that even if a future generation receives abundant food, its size would remain small.
The team hopes its findings regarding the nature of the changes in fish will help explain how stocks could recuperate if overfishing stopped or spawning grounds were safeguarded.
"If we set aside 20-30 per cent of the habitat where reproduction... of key commercial fish stocks [occurs], we are much more likely to avoid these types of problems," said Lundin.
- Atlantic fish species already shifting due to warming waters
- National fisheries rebuilding showing progress: report
By Natalia Real