An electric fishing exercise took place at the end of October at La Gachère, in La Celle-Guénand with the aim of getting to know the fish population of these watercourses but also to judge the effect of the works on the fish.
Copyright La Nouvelle RepubliqueThe principle is as follows: a generator produces a continuous rectified current of between 300 and 600 volts (400 in this case). The negative pole is placed in the water at a fixed spot; the positive pole is connected to an insulating handle with a metal ring on the end from which the current flows. Once the positive pole is lowered into the water, an electric field is created and the fish swim at first towards the source of the current. This is called "forced swimming". Swimming directly up to the researchers, they are easily caught in a landing net for they are semi-conscious. They quickly recover and do not take any lasting harm.
The species of the specimens captured is determined and they are then weighed, measured and released undamaged. Each species of fish is characteristic of a type of environment. For example, brown trout (Salmo trutta fario, truite fario) prefer cool, swift-flowing and well-oxygenated waters, whereas freshwater bream (Abramis brama, brème) prefer slower, warmer flows. The objective is to check whether a watercourse described as "salmonicole" (rapid, cool and oxygenated water) is degraded or not by studying its fish population. If the fishing exercise reveals a large number of fish characteristic of slow warm waters, it can be ascertained that the watercourse is very degraded.
The results of late October's fishing exercises in the Rémillon at La Celle-Guénand shows a quite well preserved site with the presence of brown trout and species characteristic of salmonicole watercourses:
- chabot, (Cottus gobio), [Miller's Thumb or Bullhead or Sculpin]
- lamproie de planer (Lampetra planeri) [Brook Lamphrey]
- loche franche (Barbatula barbatula) [Stone Loach]