Prolonged dry weather can cause problems on both River and Stillwater Fisheries. Long periods without normal levels or rainfall can often lead to low Dissolved Oxygen levels which can put fish at risk, especially during warm weather and where there is an abundance of weed growth. Understanding how fish are affected by this is key to running a fishery.
Fishery managers will be all too aware of the risks affecting their waters, but we hope the advice gathered together here will prove a useful reminder. This information has been put together in association with the Environment Agency Fisheries team. Full information for both stillwaters and for rivers is available to download below.
Know what’s happening with your fishery
One of the key elements for any fishery or club with waters to manage is to plan ahead. It’s essential to prepare for low rainfall and hot conditions rather than suddenly having to react when those conditions occur. It might seem like an obvious thing to say, but it’s really important that you actually know what’s happening at your fishery particularly with regards to water temperatures and dissolved oxygen (D.O.) levels, so make sure you are regularly checking D.O. levels. Remember as a result of photosynthesis, water plants and weed produces oxygen during the day, but then actually use up oxygen in the water during the night. This means that in warm conditions, oxygen levels will be at their lowest at first light so this is a good time to take a reading, as it tells you the lowest your D.O. will get under normal circumstances.
As well as decreasing oxygen levels, rising temperatures will cause stress to your fish stocks directly, reducing resilience of fish to other problems and to diseases and parasites.
You also need to be very much on the watch for algal blooms as these can lead to big changes in oxygen levels over a short period of time. It’s also key to be aware of how densely your fishery is stocked, the more crowded your waters are, the more impact low water and hot temperatures will have.
Make sure you have aeration available and know how to use i
If you start to be concerned about reducing D.O. levels then that’s when it time to use aeration. This could be as simple as having water pumps that can be used for moving water around to specialist aeration equipment such as paddlewheels. Having some aeration equipment is one thing, but do you have enough staff or volunteers trained to use it? Has it been serviced and tested prior to being needed? Do you and the rest of your team know how to safely deploy it? Do you have a plan as to where the best place in the fishery is to use it ? Using some aeration equipment in shallow, silty areas may make things worse as it will kick up large amounts of suspended silt into the water and possibly release other chemicals trapped in the silt. In some emergency circumstances you may be able to call upon the help of your local Environment Agency Fisheries team for additional support with aeration, but if you plan well, this shouldn’t be necessary. The equipment itself needn’t cost a fortune, if your club or fishery is an Angling Trust member then you get 10% off aeration devices from Aquaculture Equipment Ltd. The Environment Agency have made a great video on how to make a cheap Venturi aerator with easy to source components. You can watch the video on YouTube here.
If you had planned to stock fish and conditions are no longer favourable, it is best to delay. Not only will the new fish need to acclimatise to a new fishery, the increased stocking density will also put more pressure on existing stocks.
Let Nature Help
The key to helping river and stillwater fisheries remain more resilient during low water and hot conditions is to let nature help. Avoid too much weed cutting as weed will help river levels and provides shelter and shade for fish and invertebrates. Weed cutting will also disturb the silt and cause further problems. If you do cut weed, leave it on the bankside for 24 to 48 hours to allow any invertebrates to return to the water but then make sure you remove it as run-off can further reduce dissolved oxygen. Sometimes for angling access reasons it will be necessary to cut back overhanging trees and remove in-river woody debris, but try to keep this to a minimum, as not only does this provide shade, it also provides cover from predators. Fish stocks can be at greater risk from predation by fish eating birds and mammals during low flows, so it pays to leave the cover in place. If remove too much, to make angling access easier, you may very well find that the fish move away to find cover and you will be left with a barren stretch with very few fish to catch.
Fish care by anglers has improved hugely in the last 30 years and it is now rare to see anglers mishandling fish. However, it’s worth reminding those that fish your waters that extra care needs to be taken during low water/high temperature conditions. If you have a high number of anglers fishing a relatively small stillwater, it may be a good idea to introduce bait limits. If anglers introduce large amounts of bait, not all of it will be eaten and it will cause more issues as that bait breaks down. Why not include a link to our Blog about How Do Water Temperatures Affect Fish and Fishing on your website to keep anglers informed? In very hot conditions you could consider asking anglers to refrain from using keepnets and encourage anglers to unhook fish without removing them from the water where it is safe to do so. This is particularly important for species such as barbel, trout and salmon. Because Salmon may already be exhausted from their trip up-river and may be heavy with spawn it is key that anglers who fish for them are aware of best practice guidelines for playing, unhooking and returning fish. This excellent video illustrates these principles very well.
Finally in hot conditions don’t forget about your your own health and make sure you are well protected from the sun. Due to additional reflected light from the sun, anglers are in particular danger of sun burn, sun stroke and skin cancer if you don’t take proper protection with both clothing and sun block. So let’s look after our fisheries, our fish stocks and ourselves and have a great summer !