If you are a fly fisherman, finding a barbel run in full swing and successfully landing a big Okavango tiger will just be the icing on the cake of a truly unique African adventure.If there existed seven wonders of the fly fishing world, the annual "barbel run" in the Okavango panhandle would without a doubt be one of them. It's a yearly feeding frenzy that occurs almost exclusively in the far northern corner of Botswana, and only during a brief window when the natural conditions are at their optimum. Loud, aggressive and frighteningly effective, it is a mass congregation of feeding fish so unusual and prolific that it really has to be seen to be believed, and something every fly-fisherman just has to experience at least once in their lifetime.In spring of each year the flood water recedes from the submerged plains of the Okavango Delta, forcing schools of juvenile and other baitfish to retreat to the deeper channels as the shallow areas that have given them shelter through the winter months slowly but steadily dry up. These fish enter the fast flowing waters of the Okavango River en-masse, triggering a feeding frenzy of sharp tooth catfish (barbel) of mammoth proportions. Like a piscatorial army these slimy brown bullies march up river, gathering momentum as the receding waters continue to fuel their attack with a seemingly endless supply of petrified baitfish.Their ill-fated prey try to take refuge under the papyrus, in the roots of the floating hippo grass and under the water lilies in the shallow bays - but there just isn't anywhere to hide. Barbel, bream and tigerfish terrorise the baitfish from below, flushing them relentlessly out from their hiding places, forcing them towards the surface and even onto the river banks as they flee from the fierce attacks. But above the waterline lurks another kind of danger - fish eagles, herons and egrets lurking in the papyrus quickly snap up the hapless and panicked stragglers. It's a loud and chaotic occurrence, the splashing and slapping of the barbel, combined with the squawking and flapping of the birds and the occasional splash of a crocodile causes a huge commotion against the usually tranquil river banks.The odds are certainly not stacked in favour of these small fish, and for them this time of year is a matter of life or death. But for the fly fisherman it's simply an opportunity to indulge in some seriously red hot fishing action. Because alongside the barbel, come the highly sought after tigerfish, the 'striped waterdog' of the African waterways, lurking in the deeper channels and pouncing on any baitfish that are chased out from the banks by the marauding barbel. And the powerful and aggressive tigerfish is held is high esteem as Africa's prime freshwater target on fly.October is regarded as the month in the Okavango panhandle. The barbel runs usually start up north in the Shakawe area in September and gradually move downriver past Nxamaseri, eventually petering out just south of the town of Supupa in mid November. But on a smaller scale, the barbel in fact move upriver on a daily basis, pushing the baitfish into the strong currents and tiring them out. They will generally feed up river for a day or two, then turn and head downstream before schooling up again and making another push upriver to feed. Each time they begin their run from further downriver than the previous one, therefore slowly heading southwards over a period of six to eight weeks. And it's during this brief period that a fistful of fortunate fly fishermen converge on the area to tackle the tenacious tigers.October 2008 was no different, and midway through "suicide month" I once again found myself on the small Mack Air charter flight on my way to Nxamaseri, face pressed against the window as I watched the Okavango Delta slip past below me. Swirling mosaic patterns, formed in the grass plains by meandering streams and the winding footpaths of animals stretched out as far as the eye could see, and the occasional herd of elephants, zebra and buffalo glanced upwards as we flew over them, only 500 feet above ground. In the plane my fellow passengers chatted animatedly amongst themselves, excitedly pointing out animals and scenery as we cruised steadily northwards.It is incredible how quickly the landscape changes from arid desert to lush wetlands once you leave the town of Maun at the southern tip of the delta and pass over the buffalo fence that encircles the whole area. Dusty, scrubby land gives way suddenly to water-logged plains, bushes and lush islands dotted with date palms. Half an hour later the wide spread of green begins to narrow and soon the dizzying, twisting Okavango River appears as you enter the panhandle. It is here in the winding channels of the Okavango river that the flocks of white egrets clearly pinpoint the barbel runs taking place in various sections of the river.While this annual flyfishing adventure is very similar in so many ways to trips in previous years, there are always subtle differences that add a new dimension each time. Different sights and sounds, new bird and animal species and bigger and better runs keep the excitement at a high level. We as anglers are forever learning and appreciating more about our environment and our quarry, and that is what keeps the sport of flyfishing so interesting and dynamic.Each time I visit the delta I learn just that little bit more about fishing the barbel run. It may be anything from noticing new clues that will give an idea of where to find the runs, to a discovering a new fly pattern that the tigers just can't resist. This year I didn't fish too much, preferring to enjoy the surroundings, take photographs and allow my fellow anglers to indulge themselves in the fishing. In doing so I became more observant, picking up on the subtle nuances of the barbels behaviour, spotting new signs of what the barbel were doing and found myself better able to predict how and where they were likely to move.The runs are usually concentrated in small areas of the river and an important part of our hunt for tigerfish is to figure out where these runs are taking place each day - the most important decision being whether to head upstream or downstream from the lodge each morning. Being able to analyse them and predict how and where they will move during the day, whether they will get stronger or gradually break up, and most importantly knowing where the tigerfish are most likely to be concentrated are keys to success.Important indicators such as patches of muddy water caused by the barbel churning up the river beds, barely noticeable disturbances of the river banks and grasses by the birds hopping around above the runs, and even the specific behaviour of birds and the direction that are flying in can all point you in the right direction and maximise your success on the river.Each year the fish do something different too - in 2007 we witnessed a school of tigerfish in ankle deep water, their red fins slicing through the surface as they obliterated a school of baitfish in the most spectacular fashion. This year I witnessed hundreds of barbel in the same shallow bay forming perfect circles around the baitfish schools, then sticking their heads out of the water and opening their mouths wide - the trapped baitfish literally leaping right down their throats in a panicked attempt to clear the ever tightening circles of gaping barbel mouths. Fish eagles and yellow-billed kites hovered, dived and snatched at the fish in the air, turning the quiet backwater into a full on battle zone.Besides the enjoyment of learning more about the fishing and the environment, the birdlife on the river is simply spectacular with nearly 500 species of birds inhabiting the delta area. Islands dot the river, lush oasis' of dense bush and palms, almost every one boats a pair of adult fish eagles standing majestically on a high branch. Hearing their haunting cries and watching these big, impressive birds swooping down and scooping a tigerfish from the water is something so wonderfully African you feel it in your soul.The sounds of the bush, the birds, the fish and the wildlife is something everyone should experience - and if you are a fly fisherman, finding a barbel run in full swing and successfully landing a big Okavango tiger will just be the icing on the cake of a truly unique African adventure.