Science Articles

Space Rockets Save Fish

Wed, 27th Oct 2004

Helen Scales

Shuttle LaunchMike is a great fisherman. One of the best. So he thinks anyway, and today perhaps he might be right. The slack line pulls tight. His forehead beading with sweat, Mike struggles to reel in his prize. Held aloft, scales glittering and shining in the Florida sunshine, the specimen is a fine one. A few thousand kilometres to the southeast a small grimy outboard engine trails behind it a convulsive belch as the small volcanic island of St Lucia grows distant on the horizon. Peter sits at the tiller while his son Elijah hauls in an algae-encrusted rope. Up from the deep emerges a large trap that's been lurking on the coral reef overnight, waiting for unsuspecting fish to blunder in. Big, colourful snappers, grunts and parrotfish twitch and jump around in the bottom of the little boat. The catch is a fine one.

Fish stocks the world-over are suffering from too many people hunting too few fish. Marine parks and "no-take" reserves have been used for decades to protect fish that are left. Many studies have shown that banning fishing in a particular area leads to a boost in the number and size of fish inside the reserve. But, until now, there has been little proof that marine reserves may also benefit nearby fishing grounds.

A team of researchers led by Dr Callum Roberts of the University of York, UK, are investigating two marine reserves that are proving to help both fish and fishermen.

The fish that Mike caught was probably born in Banana Creek Reserve, a large area of estuary near the Cape Canaveral that in 1962 was closed to the public to protect the Kennedy Space Centre.

Sports fishermen are understandably competitive about who holds current world records for the biggest fish caught. As a result there are well-documented reports of the number of world record-breaking fish caught near the marine reserve at Cape Canaveral. Dr Roberts and his team scrutinised records spanning forty years and found that several years after the reserve was created there was a dramatic boost in the number of trophy fish that were being caught in the region compared to the whole of Florida. The waters around the reserve "have become a honey pot site for catching spectacular fish," says Dr Roberts.

Fish inside marine parks find a safe haven from the arsenal of fishing hooks, lines and nets they might otherwise encounter. They can live for longer and grow bigger than fish outside a reserve. The fish in this study, such as the spotted sea trout, make immense underwater journeys during their lifetime. Some of the fish that grow fat and healthy inside a reserve eventually wander across the watery reserve boundaries and meet the hook of a soon-to-be champion fisherman. Fish migration from marine reserves can supply nearby fisheries with potentially prize-winning fish. Prize winning in Florida, but elsewhere those are meal-winning fish.

Back in St Lucia, a series of small coral reef reserves was created in 1995 to try and rescue the threatened fish stocks on which many fishermen, like Peter and Elijah, rely for their food and livelihoods. Fishing is still allowed in areas of reef nestled amongst the network of park areas, but initially the fishermen were worse off than before. "The fish catch was of low value due to too much fishing in too small an area," says Dr Roberts.

This problem didn't last too long. The research team carried out underwater counts of fish size and numbers. They have shown that after three years there was three times the number of fish inside the reserve and twice as many outside compared to before the park was set up. Dr Roberts' team also monitored the fish being caught by fishermen. Since the reserve was created, fish catches have increased in total weight by between 43% and 90%.

As well as the migration of long-distance swimmers out of marine reserves, another mechanism is at work to boost fish stocks outside protected areas. Bigger fish make more eggs than smaller fish. So the bigger fish inside the reserves produce lots of eggs. Fish eggs and the tiny larvae they hatch into may drift out of reserves on ocean currents into areas where they "seed" nearby fisheries, like a farmer scatters seed over his land.

So, whether a marine reserve is set up to protect space rockets or with the specific aim of preserving fish stocks it seems that fishermen of all shapes and sizes can truly benefit. Hopefully this, and other studies, will provide enough evidence to persuade governments and fishing authorities to create more and more marine reserves in the race to protect this precious and ever-threatened resource.

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