Summer Weed Growth

The logic behind weed growth is somewhat confusing. Last year, two of the stillwaters I fish were top to bottom with heavy weed, this year they are almost completely clear.

A smaller water that I visited today that has never really suffered badly with weed was afound to be almost unfishable today.

What have your experiences been this year and do they follow any real pattern to enable predictablility?

True, its very difficult to find a pattern with weed.

I used to think it was about temperature...if it was warm the week would be shooting up but if it was cold then there would be less. Nowadays I think sunlight plays a bigger part and the more direct sunlight there is the better the weed growth will be. Of course there will be 1001 other factors both natural and man made involved but just as a general observation. This year on my rivers the water levels were higher and coloured for allot longer than normal and I noticed the weed growth did not take off anything like it has in other years.

I'm not sure that you can put your finger on any one statistic to any given area. Weed growth seems to go in cycles (what dictates these cycles I'm not completely sure). As Philip says direct sunlight obviously plays a big part and you can virtually guarantee that very shady parts of the river will be substantially less weedy.
Jerry

In the summer months I fish a 50 acre pit for carp. Usually the weed, mainly Canadian, is very bad with the water being very clear (water clearing as the weed grows). The Canadian has not grown so much this year but a lot of what has grown is fairly black in colour. However; there has been a massive explosion of daphnia (I've never seen so much) which had coloured the water (now disappearing), loads more bloodworm than usual and recently there has been a very bad algea bloom with literally billions of green blobs of the stuff drifting at all levels of the water with a light green paint effect on the surface in the more sheltered edges. The carp fishing has been even slower than usual which I put down to the abundance of daphnia? Any thoughts, considering that generally this has been a slightly cooler summer than most?

The cycle for Canadian pondweed is all about nutrients available in the water. When there is a lot available the weed grows very well until there is no more available nutrients a which point it stops. The weed dies with the nutrients locked up in the weed. Over the next two or three years the weed rots releasing the nutrients and the cycle starts again, hence a three or four year cycle of weed growth/no weed.

weed is removed from the river when it is cut back and put on the bank. I guess it could follow that this breakdown still releases nutrients into the river when they wash in.

Living in an agricultural area, phosphate and nitrate wash in has historically been a problem.... are there weeds you can plant that out compete nuisance plants/weeds and strip out the nutrients to help control the problem?

Mark Wintle said:

The cycle for Canadian pondweed is all about nutrients available in the water. When there is a lot available the weed grows very well until there is no more available nutrients a which point it stops. The weed dies with the nutrients locked up in the weed. Over the next two or three years the weed rots releasing the nutrients and the cycle starts again, hence a three or four year cycle of weed growth/no weed.

Click to expand...

Cheers for that Mark, I always wondered what was the key influencer.

chav professor said:

weed is removed from the river when it is cut back and put on the bank. I guess it could follow that this breakdown still releases nutrients into the river when they wash in.

Living in an agricultural area, phosphate and nitrate wash in has historically been a problem.... are there weeds you can plant that out compete nuisance plants/weeds and strip out the nutrients to help control the problem?

Click to expand...

There was a big idea to have buffer zones along rivers - a vegetated strip of land 5-10m wide (ideally with marsh plants) that could intercept nutrient-rich water and silt from surrounding ploughed fields etc. Dont think this idea got anywhere though.

A similar principle can be used to a "point source" such as a tributary ditch that is enriched - at the point of entry to the river it could feed into a constructed wetland area. Idea being that marsh plants will trap and take up the nutrients and polluting solids. Reedbdeds are good at this. The EA has built the odd one here and there to tackle polluting surface water drains in urban areas.

As for the plant growth, light, temperature and nutrients are all important. Water fleas that are harboured by the weedbeds also help to keep the water clear by eating phytoplankton - microscopic algae suspended in the water column. Once fish have spawned, fish fry then eat the zooplankton and this can make the water get more turbid as phytoplankton develops unchecked - usually during mid-late summer. This turbidity and competion for nutrients can then check further weed growth by large submerged plants. So theres a few variables all interlinked and fish fry play their part - which may help explain the variability year to year.

Marks point about nutrients and Elodea is spot on - same also applies to phytoplankton in late summer if that is dominant, as once the nutrients are no longer available the water may clear as it dies off. I think it is under those circumstances when nutrients are limiting factor that blue-green algae (paint-like scums etc) can sometimes take over for a while - but i am not sure about that.

Some interesting responses here - thanks!

If its a worry then the response /solution I had last week from a young angler who had stepped outside the commercial fishery scene for a try on a water I was fishing said simply--"If this was a commercial they would be round with the boat to scoop it all up then we can all get to the fish!"
Simples!

flightliner said:

If its a worry then the response /solution I had last week from a young angler who had stepped outside the commercial fishery scene for a try on a water I was fishing said simply--"If this was a commercial they would be round with the boat to scoop it all up then we can all get to the fish!"
Simples!

Click to expand...

I was digging around the edge of a lake in amongst a load of weed with my landing net the other day - i just wanted to see a fish having been blanking for about 6 hours at that point - and it was teeming with baby tench about an inch long. At this lake i had experienced anglers say to me we should pull all that lot out as i gets in the way of the line.

Maybe thats why we dont see many tench on many waters anymore?

chub_on_the_block said:

I was digging around the edge of a lake in amongst a load of weed with my landing net the other day - i just wanted to see a fish having been blanking for about 6 hours at that point - and it was teeming with baby tench about an inch long. At this lake i had experienced anglers say to me we should pull all that lot out as i gets in the way of the line.

Maybe thats why we dont see many tench on many waters anymore?

Click to expand...

Kinda figures chubby!