Waters & words

Posts tagged “trout withstanding drought

Lessons from the landscape: how low do they join

Many forays from my home waters to the streams of the North Eastern Cape highlands, have got me thinking about the differences between those waters, and the ones nearer my home.

The climate is drier up there, and the veld can be positively scrub-like compared to our lush, humid midlands of KZN.  The rivers also flow southward or south westward, whereas all the home streams flow towards the east.  We have a lot of Brown Trout streams here at home, whereas around Rhodes and Barkly East, the waters are mainly Rainbow waters.  Our rocks, especially in the lower reaches, are black, angular and slippery, whereas the NE Cape has sandstone bedrock or fine gravel for the most part, making for easier wading.

But here is something that perhaps sets the area apart:

In KZN, our streams tend to flow down from the Drakensberg in a relatively straight path, and quite quickly descend below the 1200m contour, BEFORE they are joined by their neighbouring streams. What I mean by this, is that there are relatively few junctions of major rivers within the area that can sustain trout.

The significance of this, is that the KZN trout have limited (Very limited!) opportunity to travel down one valley and up another. This means that the genetic make up in one valley could arguably be completely separate and potentially different from the next valley.

Another aspect to consider, is that when a stream dries up in the North Eastern Cape, it’s Trout population can be restored from another artery when the stream begins to flow again.  This is very seldom the case in KZN.

The situation in the Cape is as a result of a jumble of mountains, with rivers and streams that cut through them in a variety of directions, and with the land sloping off to the plains very gradually. This allows rivers to meander and intersect at higher altitudes.

Sterkspruit-10

I suppose this makes our trout in the KZN rivers more vulnerable. If a drought or pollution incident were to befall the trout of one valley, it might not quickly receive some fresh bloodlines to re-populate it from another.     In the NE Cape, after the severe droughts of 2015/6, we all saw photos of the Sterkspruit so dry that not only did it cease to flow, but the puddles started to dry out.  A visit to the area this year, revealed that the streams are again full of countless small trout.  It really is quite miraculous!    This miracle is no doubt aided by the fact that just a few trout had to survive in 1 or 2 of the streams, and the re-population of all streams after the drought would surely happen given time. 

Confluences of trout rivers are an important feature…..