Growth in­dus­try

When weed starts se­ri­ously do­ing its thing, fish­ers and fish­ery staff alike must get to work. Peter Cock­will as­sesses the prob­lem and of­fers some so­lu­tions

Trout Fisherman (UK) - - Contents - Words:

How fish­eries and an­glers can deal with weed

IF fish­ing had its own Room101, weed and mos­qui­toes would prob­a­bly be cheek-by-jowl in the ‘IN’ tray. Both are ir­ri­tat­ing, sneak up on you, are im­pos­si­ble to deal with and ap­par­ently serve no use­ful pur­pose. If you are a fish­ery owner then weed is your worst night­mare, be­cause it grows at an alarm­ing rate, and is hugely ex­pen­sive and time-con­sum­ing to deal with; plus its re­moval is in­vari­ably ac­com­pa­nied by a choir of whinge­ing cus­tomers. Should you be a trout, how­ever, then weed is a de­light, be­ing home to all man­ner of crit­ters that you like to eat. It also pro­vides cover from the sun, pro­tec­tion from preda­tors, hu­man and avian, and dou­bles per­fectly as a home and am­bush lo­ca­tion. Like­wise, if you are an aquatic in­sect, or a baby fish, the weed gives you a home and food, and also life through the oxy­gen that is pro­duced by pho­to­syn­the­sis. Find­ing the happy medium be­tween weed’s con­founded nui­sance value and the boon it rep­re­sents for a fish­ery can be chal­leng­ing. Depend­ing on which side of the counter you stand, there you are in high sum­mer, an­tic­i­pat­ing ei­ther some lu­cra­tive foot­fall or a wel­come day’s fish­ing, only to find that what you thought would be a per­fect day is in fact blighted by weed, foul­ing line and fly alike with ev­ery cast and per­suad­ing po­ten­tial cus­tomers to stay at home and await bet­ter days.

So, what’s the so­lu­tion?

Well, for the an­gler, there are quite a few. The first is to check your cho­sen fish­ery web­site for cur­rent con­di­tions and back it up with a tele­phone call or email en­quiry. Be pa­tient, though: if it’s a busy time, the owner/man­ager and staff may well be out on the banks dur­ing the day so don’t ex­pect an in­stant re­sponse to all your en­quiries. Any fish­ery worth its salt will be hon­est about fish­ing prospects but they also can’t cater for ev­ery level of abil­ity. Hav­ing checked what the fish­ery is do­ing to mit­i­gate the weed prob­lem, you must now ac­cept that you too have to ad­dress the sit­u­a­tion - it’s no good ex­pect­ing to fish the place the same way you did when last there, when the wa­ter was less clut­tered. Be pre­pared to adapt to the changed cir­cum­stances and weeded wa­ters can still be fished suc­cess­fully. Check the point­ers I have pro­vided in the panel ac­com­pa­ny­ing this ar­ti­cle.

“If weed were hu­man, it would be tested for steroids: its bulk aside, mare’s tail can eas­ily grow 15cm in a week, rib­bon weed dou­ble that...”

Now to ad­dress the prob­lem from the fish­ery’s point of view. For starters, it is no longer pos­si­ble to con­trol aquatic plant life with chem­i­cals. All such op­tions were out­lawed from 2010. That leaves the fish­ery with the pos­si­bil­ity of us­ing bi­o­log­i­cal con­trols, which can be pretty ex­pen­sive on any lake over a few acres and which call for care­ful tim­ing. Lock­ing up the nu­tri­ent base (phos­phates and ni­trates) is a de­vel­op­ing tech­nique and es­pe­cially ef­fec­tive with the base al­gae prob­lems of early sea­son, which give fish­eries the dreaded ‘ris­ing scum’.


An­glers will have seen bar­ley straw in­hibitors em­ployed as rot­ting straw in nets, but they can also take the form of a liq­uid ex­tract, which work bet­ter for al­gal con­trol than plants. Coloured dyes in­hibit pho­to­syn­the­sis, and are ef­fec­tive, although the re­sult­ing wa­ter colour (blue or black) can be off-putting to an­glers. They should be re­as­sured that this method works and has no ef­fect on in­ver­te­brate life. If you want to keep things ‘or­ganic’, then we reach the el­bow-grease op­tion of me­chan­i­cal con­trol – cut­ting the weed and re­mov­ing it. If done with man­ual chains and scythes, those do­ing it will need to be fit and strong. It’s far bet­ter if the fish­ery can af­ford its own weed-cut­ting boat (or hire one). Some boats have a lift­ing frame to dump cut weed on the bank, while oth­ers just cut it. Whether it’s you or ma­chin­ery (such as a mini-dig­ger) that even­tu­ally gets the weed onto the bank, it will then have to be moved off-site for dis­posal. You won’t be­lieve how much weed can be har­vested from just one acre of wa­ter, nor how heavy it is. If weed were hu­man, it would be tested for steroids: aside from its bulk, the likes of mare’s tail can eas­ily grow 15 cen­time­tres in a week, rib­bon weed dou­ble that, and I some­times think you only need look at elodea (Cana­dian pondweed) to trig­ger a growth spurt. Fish­ery life can eas­ily lose some of that ‘easy num­ber’ sta­tus that it strangely en­joys in the eyes of cer­tain cus­tomers, once this fast-grow­ing mon­ster needs rein­ing in, and I’ve men­tioned just a few of the many species of aquatic plants that can choke a fish­ery half to death. Star­wort makes dense beds of growth which are re­ally te­dious to get out and then there are mar­ginal plants like bul­rushes and reeds and all man­ner of fast-grow­ing wa­ter crow­foots (ra­nun­cu­lus). Now add in the fil­a­men­tous al­gaes such as ‘cott’, more com­monly called blan­ket weed, or the more sim­ple ‘blue-green’ types which can bloom un­con­trol­lably, and run­ning a fish­ery be­gins to feel more like wag­ing a war. Any of these weeds or al­gae can cause im­mense de­oxy­gena­tion at night, when they pro­duce car­bon diox­ide in­stead of the ox ygen that they churn out in day­time, and even their demise is no im­me­di­ate cause for cel­e­bra­tion. Fol­low­ing a sud­den die-off, the sub­se­quent de­com­po­si­tion of these plants can usher in an­other oxy­gen crash. You will of­ten see fish­eries run­ning aer­a­tors, es­pe­cially overnight, to try and coun­ter­bal­ance these prob­lems and a hu­mid, thun­dery night can amount to the per­fect storm. In essence, there’s no cure-all for aquatic plants and al­gae, with ev­ery fish­ery fac­ing its own spe­cific prob­lems, of­ten based on wa­ter qual­ity. For ex­am­ple, low pH or acidic wa­ters, with very lit­tle in the way of or­ganic nu­tri­ents, usu­ally have min­i­mal plant life and rarely get al­gal blooms or ex­ces­sive weed growth, whereas wa­ters in fer­tile farm­land, rich in nu­tri­ent run-off, can see phe­nom­e­nal growth rates once tem­per­a­tures start to climb, trans­form­ing fish­ery con­di­tions from ideal to weed­choked in as lit­tle as a week. Then there are the nat­u­rally high pH wa­ters, as in the chalk-base re­gions, which also have ideal con­di­tions for nur­tur­ing aquatic plants and which can also see con­di­tions change whole­sale in just a mat­ter of days – yes it can hap­pen as quickly as that, then the hard work be­gins.

Peter Cock­will

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