While our lower Zambezi does experience some degree of flooding each year, it is nothing like the Barotse. In spite of the massive flooding on the upper Zambezi though, tigerfish did not really behave vastly differently during high water, mostly preferring the main channel of the river. The report continues “Tigerfish did not undertake long-distance migrations onto the floodplains, but mainly utilised the adjacent temporary water covered areas. All the fish were recorded in the mainstream of the river, and on average, 81% of the fixes (average of different individuals) were in the main river. However, the tigerfish were to an increasing extent recorded in habitats such as side channels, backwaters and floodplains during rising water level. Although often recorded in the main river channel, tigerfish rather stayed closer to shore than in the middle of the river. The fish were recorded on average 107m from the nearest shore (69m during low, 68m during rising and 356 during high water), which constituted 22% of the total width of the river (25% during low, 23% during rising and 28% during high water).”

 

As techniques have evolved in recent years, and more and more anglers are targeting tigerfish with flies and lures in the margin riverbank areas of the river, it seems that contrary to traditional thoughts, the tiger do utilise vegetation and structure more than one might think. “The fish were also likely to be associated with vegetation, but they were never recorded inside or under vegetation. The most frequently recorded vegetation type was marginal aquatic anchored vegetation. Water depth where the fish were recorded varied between 0.5 and 14.0m, and was on average 3.8m. Water temperature during the study varied between 20.7 and 30.1 ºC.” they reported.

 

It was obvious from their study that tigerfish are vulnerable to over-exploitation as 26% of their tagged fish were recaptured, often in nets. Given that tigerfish both occupy relatively small ranges for periods, then move longer distances, any management strategy needs to have the support of all stakeholders and even governments if it is to really work. They conclude “Co-ordination of local and regional management regulations are important for the tigerfish populations, to avoid fish being protected in one river section and depleted in the neighbouring river section. In rivers bordering on several countries like the Upper Zambezi River, multilateral management regulations are needed as well, especially for long-distance moving species as the tigerfish. However, tigerfish may be less vulnerable to high exploitation in a specific area than more stationary species. The long distance movements of some individuals makes it likely that a locally depleted population can be re-colonised by tigerfish moving from other areas, even tens of kilometres away.

 

“The stationarity of some of the tigerfish also implies that smaller sanctuaries can protect adult fish, because some of them may be staying in the protected area. However, smaller sanctuaries will not protect the long-distance moving fractions of the tigerfish population, and when management actions to protect tigerfish are needed, gear or effort restrictions may be more effective. A more detailed study of the activity patterns of the fish throughout the

day would provide information on the vulnerability of the tigerfish for being caught in passive gears, such as gillnets. The long distance movements also suggest that tigerfish populations may be vulnerable to dams and other migration barriers.”

 

Part of our own rambling conversations explored the idea that maybe the fish populations have not necessarily declined to the extent imagined, but rather the fish have become wise to anglers due simply to the increasing number of people on the river. Indeed, studies on bass have shown they are able to ‘learn” and avoid dangerous or uncomfortable situations, and as ongoing research is constantly showing, fish are capable of a great deal more than we have given them credit for. Static populations may indeed be growing accustomed to us simple anglers.