Sea fish stocks ‘running out’

A major investigation of marine ecosystems around the world predicts their wholesale collapse in the next 40 years.

If nothing is done to reverse the trend, in a mere four decades, little sustainable fish or sea food will remain.

At this point, commercial fishing will no longer be viable.

The extent of the crisis is revealed in one of the most wide-ranging and thorough studies of marine biodiversity trends ever conducted.

Researchers first analysed the results of 32 experiments that manipulated the fate of marine species on small local scales.

Next they tracked 1,000 years of change in species diversity across 12 coastal areas.

In each one they looked at trends affecting between 30 and 80 economically and ecologically important species, drawing information from old archives, fishery records, sediment cores and archaeological data.

Then the team sifted through all the available catch records for 64 ocean-wide regions spanning the years 1950 to 2003.

Collectively, these large marine ecosystems (LMEs) produced 83 percent of global fisheries yields over the past 50 years.

Finally, the scientists investigated the recovery of biodiversity in 48 marine reserves and areas closed to fishing.

Study leader Dr Boris Worm, from Dalhousie University in Halifax, Canada, said: “Species have been disappearing from ocean ecosystems and this trend has recently been accelerating.

“Now we begin to see some of the consequences. For example, if the long-term trend continues, all fish and seafood species are projected to collapse within my lifetime – by 2048.”

Almost 30 percent of fished species populations had already reached this tipping point in 2003, according to the findings reported in the journal Science.

Despite more intensive fishing, cumulative yields across all species and ocean ecosystems had declined by 13 percent, or 10.6 million metric tons, since 1994.

The research clearly showed that increased marine diversity led to greater stability and sustainability of fish stocks.

Fishing was only one human factor affecting marine biodiversity, said the scientists.

Pollution, habitat destruction and climate change all took their toll on fish species.

Loss of fish from the oceans had harmful knock-on affects, including a deterioration of water quality, less protection of shorelines, oxygen depletion, and higher numbers of toxic algal blooms.

“Whether we looked at tide pools or studies over the entire world’s oceans, we saw the same picture emerging,” said Dr Worm.

“In losing species we lost the productivity and stability of entire ecosystems. I was shocked and disturbed by how consistent these trends are – beyond anything we suspected.”

However it was not all bad news. There was still hope for the oceans, if action was taken now, said the scientists.

In protected areas, efforts to improve marine biodiversity had increased species richness by an average of 23 percent.

These gains were associated with big increases in fishery productivity in areas around the reserves.

“It is not too late to turn things around,” said Dr Worm.

Commenting on the report, marine conservation biologist Professor Callum Roberts, from the University of York, said: “For generations, people have admired the denizens of the sea for their size, ferocity, strength or beauty.

“But as this study shows, the animals and plants that inhabit the sea are not merely embellishments to be wondered at. They are essential to the health of the oceans and the well-being of human society.”