Creating barbel and chub spawning areas by cleaning gravels. This video shows creating/cleaning the spawning gravels, that have become solidified with silt, algae and other pollutants. Late April and early May is the time of the year to clean or create spawning areas. If barbel, chub or other species spawn naturally in our rivers they are more likely to have a built in/evolved wariness to predators such as otters, mink and cormorants than if they were stocked from a hatchery. Also, there is a natural instinct, when and if they become mature, to return to the spawning area where they hatched.
Nutrients are put on fields during farming, including chemical fertilisers and animal manure. Sometimes, this can be more than is required and excess are washed into waterways during rain, storms and snow events. These get washed downstream in the form of phosphates and mineral nitrogen and can cause algal booms that can clog up the alluvial gravel on the shallow stretches of our rivers. Also, untreated or partly treated sewage released by the water authorities, that we've heard so much about on the news recently, has similar detrimental effects. There are also a lot of other particles washed off our fields, roads and built up areas. One of the things that happens from combinations of the above, is that the gravels often become effectively, glued together and hardened so the fish can't create spawning redds. If the gravels are suitable, the female fish create these redds in the gravel by swishing their tails and lower body from side to side, to create a hollow, to lay their eggs in. If the gravels are solidified and the eggs are laid on top of them, they are more likely to get eaten or washed away.
I'm sure most angling clubs will be aware of the areas where the chub and barbel gather to spawn or try to spawn and these are the areas that should be selected for the gravel cleaning. Once the Environment Agency is aware that the club concerned has done this work, they are more likely to release stock fish there.
We'd got two Honda WB20 water pumps that send out very powerful jets of water into the gravel to wash away the hardened silt and other impurities. These can be borrowed or obtained from the Environment Agency. Often, heavily silted up and solidified gravel needs to be broken up with a garden fork, before the metal tube if the water jet can be inserted into the gravel to jet out the muck.
As you can see from the video, we had one person on the pipes coming out of each of the pumps and others working with garden forks to loosen the gravel and lift it up, so as the current can wash away the silt. It took a couple of hours to prepare each area.
The barbel and chub should be on each of the areas in May or June, in water between 12 cm and 80 cm deep and, in our experience on the Great Ouse, the water temperature needs to reach about 17 degrees centigrade.
In my next video, I will show stocking the Great Ouse with chub, barbel and dace.
18 сен 2024
