Surveying and Stock Management

The A.G.A. Group can carry out electro-fishing, seine netting and trapping methods to both assess fish populations and to remove stock, including unwanted predators.  

We are often asked to attend angling waters to carry out surveys of the stock, and on a regular basis our investigations will reveal that it would be beneficial to the health of the fishery to reduce the stock biomass in it .  The concept of removing stock as a way of improving the angling catches from a fishery can in our experience be a difficult one for anglers to come to grips with, so perhaps a few words of explanation may be appropriate.

In a heavily stocked fishery situation where there is a combination of either too many of a particular fish species (out competing other species and each other) or that there simply are species stocked that interact poorly together in a fishery, then stress is likely to be present in a chronic form.

The stress will often be as a result of the naturally occurring hierarchy's that regulate fish populations in fisheries where man has no part. However these hierarchy’s which are largely involved in competition also cause stress in the somewhat unnatural environment of a recreational fishery.

The stress is largely induced by competition between species that would naturally not occur, and by competition between individuals as a result of species populations that have become unbalanced in their dynamics or structure.  This can simply happen because of poor breeding success and recruitment, with year classes being absent from the population.

This is one reason why proper surveys should represent rather more investigation than just running a net through the fishery and gazing lovingly at a net full of fish.  The scene as shown in Plate 1 is leasing to the eye but in real terms tells you very little about the fishery unless it is put into context with other factors.  There can be many varied reasons for carrying out stock removal Plate 2. shows a netting removal below a coffer dam to allow the Environment agency to construct a new in-stream  structure and fish- pass.

Plate 1.   A net full of fish does not tell you very much about a fishery in the grand scheme of things.  More investigation is required before a management plan is developed.

Plate 2.   A fish-rescue carried out for the Environment Agency (Thames region) below a coffer dam on the River Lodden (May 1999)..

It is very useful to look at netting results with the benefit of the knowledge of how the fish stock have performed in the past, this can be achieved by looking at past growth rates and how these rates compare with national averages.  Plate 3. shows a fish scale it is a good example of a scale that can be used to determine both the age and past performance of an individual fish.  Plate 4. shows a graph of the information that is obtained when scale readings are combined with weight and length data.

Plate 3.  A rudd scale which shows the annuli (yearly growth rings).  The distance between rings is used to assess comparative annual growth.

	Plate 4.   Graph showing an actual analysis of an AGA fishery showing that in 1994 the growth of bream was significantly different from standard growth curves.

But removing fish can usually only be really effective for improving angling when it is carried out as part of a management plan which considers the habitat and wider ecology of the fishery. It is only when you manage fisheries at this holistic level that one can expect to see tangible improvements to the angling results. Simply put, removing fish will reduce chronic stress levels, fish free from stress will feed more freely, breed more prolifically, this may in turn result in a harvestable surplus that is worth money, which you can be used to bring about further improvement to the fishery..

Telephone Ash to discuss how the A.G.A. Group might carry out a survey to supply critical management information and to remove stock if so required. 

We would wish to emphasis that we do not want to buy your fish, we are willing to sell them for you ( we charge an administration fee).  This way you make more money and we can honestly say (and be believed) that we do not advise clients to remove fish to buy them on the cheap and make additional money, many do.

The A.G.A. Group are not fish dealers!