Improving trout spawns
A fishing syndicate that
I am a member of is keen to increase the number of brown trout spawning successfully in a stretch of river. What can we do prior to spawning to maximise our success?
The female trout must dig a redd in which to spawn. It does this by holding station in the stream and moving gravel with its tail until there is a depression in the river bed with a small heap of gravel. When male fish are present she will take up a position in the depression and release her eggs at the same time as the male releases its milt. Fertilisation is a hit-and-miss affair in the fast-flowing water and the fertilised egg must become lodged in the heap of gravel at the back of the redd.
Compacted spawning gravels will impact on the success of trout spawning. Some people jet-wash known spawning gravels in October, well before the trout have taken up residence, though this is quite an aggressive action. Many years ago, some chalkstream keepers would have a horse drag a harrow across the gravels to loosen them; others preferred a more hands-on approach and used rakes.
Each October I spend a few hours shuffling around the shallows, facing upstream with a 6ft length of corrugated tin placed horizontally across my legs and resting on my toes. This stretch is blessed with relatively loose gravel and the draught of water under the sheet of tin is sufficient to tickle up the gravel and keep it loose enough for both trout and grayling spawning.
Avian predation, particularly by herons, can also impact on the spawning success of brown trout, which are especially vulnerable in shallow water to a bird that will stab away indiscriminately at what is placed before it. I will always leave any bankside tree work until after spawning has finished to provide as much cover as possible to spawning fish. CDC
Brown trout are particularly vulnerable to herons