Commercial - Fish Removal
Our staff are specifically trained in fish removal from all water bodies from lakes of several hectares, through to rivers and even storage reservoirs and ponds.
We use seine nets to remove coarse fish and trout and these nets vary in size according to the situation. For small pools and rivers we have nets as small as 15 meters long and 1.5 meters deep. For larger pools and rivers we have 50 meter nets that are 3 meters in depth. For deeper lakes we have 70 meter nets that are 6 meters deep, and our largest nets are 100 meters long and 4 meters deep.
When using seine nets the effective fishing depth is two thirds that of the net depth. The net is placed around the margins of the water and slowly retrieved. Corks keep the net floating at the surface and lead weights keep the bottom of the net on the lake bed. As it is retrieved a “curtain” of net crowds the fish to one area where they can be removed with hand nets.
Netting is an art, and using the most appropriate net in the most appropriate fashion is the skill required to achieve maximum removal efficiency. The maximum removal efficiency that can be achieved even in a perfect pool with no variation in lake depth, and devoid of aquatic plants and debris/snags, is 70%. Therefore 30% of the fish population will still be present. This can be improved upon by reducing water depth prior to netting but there will always be a proportion of fish left after seine netting.
An alternative method to seine nets is electrofishing. This involves placing a carefully controlled electric current into the water which temporarily stuns the fish allowing them to be removed from the water. They are immediately placed into aerated tanks of clean water where they are allowed to recuperate.
This method of removal is suitable for clear water bodies that would otherwise be too difficult to seine net. Such waters would include rivers and streams, as well as still waters with excessive aquatic plants, varying depths or debris and snags. Our staff are fully trained in the use of this potentially hazardous equipment and adhere to the Environment Agencies code of conduct for electrofishing.
We use a boat mounted WFC4 apparatus which can fish up to 15 amps, sufficient for most waters although the maximum effective fishing depth with this apparatus is around 2 meters. The shallower and clearer the water, the more effective this method is.
The only way to ensure 100% fish removal from any water body is to completely drain the water down after using seine nets and possibly electrofishing apparatus, depending on the circumstances. Once the water is carefully removed, ensuring any environmental regulations are adhered to, the fish are literally picked out of the water and transported away
We are able to utilise these specialist techniques in order to evaluate fish stock numbers, sizes, species and age - otherwise known as surveys. We use data analysis to estimate the total stock in a water by repeating a netting or electrofishing “run” several times and plotting the results on a graph to estimate total numbers. This is known as the depletion estimate. We also utilise other data analysis techniques appropriate to the situation. With this information we are able to advise fishery owners on future management plans in order to get the best from their water.