Around twenty years ago off the coast of Inish Mor a basking shark rose up out of the water and terrified an eight year old boy who had been taken fishing by his father. The vast shark with it's enormous mouth was almost the size of the fishing boat, and the boy cried and shuddered and asked to be taken home. Twenty years later the boy has grown up, has children of his own and a rather different problem.

This is a story about fishing, about an island and about a tour guide who's name I have forgotten, even though I only met him about six weeks ago and really meant to remember. He lives on Inish Mor, where he grew up and like most of the people on the island he works a number of jobs - tour guide, farmer, artist and so on.

When he was young his father took him fishing off the island, and he could catch all kinds of fish. There were dozens of species in the harbour, and more off the coast, including the vast basking sharks - fish so huge you could watch them from the cliffs if you were lucky. Now he told me all these are gone, the industrial fishing fleets have fished out the waters around the islands.

For a few years my tour guide worked on the fishing boats, in his case Spanish ones. 'It's the mesh size they use' he told me, referring to the size of holes in the net. 'They set it too small so the young fish get caught before they have a chance to breed'. As traditional fish stocks are depleted fishing methods have become ever more destructive and the proportion of bycatch - unwanted fish thrown back dead - has gone up.

This is a problem in all sorts of ways - and not just because he can no longer take his kids fishing and be confident of catching something. Because fish like cod is no longer local and plentiful the local chip shop costs more. Because the local fish stocks are fished out jobs on the fishing fleets are harder to come by and less pleasant - lasting longer and taking the men further afield for less money.

The solution to all this isn't that difficult, fish stocks need to be protected from exploitation and allowed to recover then fished sustainably. A permanent Lundy Island has achieved great results but it's a tiny part of the world.

Research and experimentation has shown that where reserves are established and fish stocks allowed to recover surrounding areas also benefit. Fish are after all, blisfully unaware of whether or not they are protected and don't stay inside the boundaries. The problem is, of course, political. Less fishing today means less money for fishermen today. Then there are additional squabbles over quotas and whether government x, y or z is doing it's part to stop pirate fishing.

So what hope is there for marine reserves? Well things are looking up. Many government appointed bodies have recommended them. A new EU law is being proposed, called the Marine Strategy Directive which may go a long way to achieving the necessary results. Why not write to your representative and encourage them along?.

So, if like my Irish tour guide you'd like to be able to dine on fish you caught yourself, or take your children out to be terrified by basking sharks what can you do? Well you can watch what you eat, ask your fishmonger about where his fish come from, or try to find out if your local supermarket source their fish in a sustainable manner. If we get this right the oceans could be a bountiful source of food for generations to come. If we get it wrong the oceans will be empty.