New predator study can reveal much about our rivers

For a while now Dilip Sarkar and myself have been discussing the results of various studies that have examined predator fish populations around Europe. Some of the results of these studies were fascinating and gave a real insight into the spawning movements, hunting range, favourite prey and growth rates of pike and zander in other parts of Europe.

There are some amazing predators living in the Severn, Avon and Wye, yet we know so little about them.

There are some amazing predators living in the Severn, Avon and Wye, yet we know so little about them.

At about the same time as Dilip and I were looking at these studies, anglers on the River Severn and Warwickshire Avon were expressing their concerns about the apparent decline of silver fish stocks in many parts of the river. These concerns were raised with the Environment Agency, but unfortunately due to a lack of data it was very hard to prove that roach, dace, chub and bleak were in decline. The normal method of assessing fish stocks is to electro-fish a section of the river on an annual or bi-annual basis and compare the results of the bio-mass of fish that is discovered year on year. The problem is that it is pretty much impossible to electro-fish the Rivers Severn and Avon due to their width and depth. Historically anglers match catch data has been used as a way of monitoring fish stocks, but this is an inexact science at the best of time and with the number of large matches regularly being held on the rivers declining markedly in recent years it is now no longer a particularly viable option.

Brecht Morris and colleague of the Environment Agency with some beautiful roach rescued from Pitchcroft in Worcester during recent floods. While there are still some fantastic silver fish in the river, there have been many concerns about fish stocks overall in recent years.

Brecht Morris and colleague of the Environment Agency with some beautiful roach rescued from Pitchcroft in Worcester during recent floods. While there are still some fantastic silver fish in the river, there have been many concerns about fish stocks overall in recent years.

So Dilip put his thinking cap on and came up with the idea of a predator study which would not only help us learn far more about the lives of the pike and zander in our rivers, but would also act as a barometer of the health of prey fish stocks at the same time. This idea was showcased at a meeting in Worcester last year which was attended by keen predator anglers and representatives of the Severn Rivers Trust and The Environment Agency. The EA thought the study was an excellent idea and Fisheries and Biodiversity Technical Officer, Brecht Morris was assigned to help make things happen.

Dilip Sarkar who came up with the idea of the study with a cracking Severn Zander.

Dilip Sarkar who came up with the idea of the study with a cracking Severn Zander.

So How will the Study Work ?

The key to the study is that anglers are absolutely central to it’s success. Any angler who fishes for Pike and/or Zander on the rivers Severn, Warks Avon or Wye can get involved and will be given free training. Once trained up, they will be given a small kit which includes everything needed to take scale samples and record their catches properly. Every time they catch a pike or a zander on one of the three rivers they will record it’s weight, length, time of capture and take note of which 5 miles section of the river it was caught from. They will then take a photo ID shot of the fish and remove three scale samples. The fish will then be returned unharmed to the river.

The first batch of Predator Study volunteers assemble ready for training.

The first batch of Predator Study volunteers assemble ready for training. A Huge thanks goes to Kinver Freeliners for letting us use their lake and fish for the scale sample training.

It’s vitally important that this process is carried out for all the fish that the anglers catch, as the growth rates of small jacks and juvenile zander are just as important to the study as specimen fish. At the end of the season the anglers will submit their catch data and scale samples to the EA who will log the data and analyse the scale samples to assess the growth rates of each fish.

Brecht Morris gives instructions on safely taking scale samples at the first Predator Study Training Day

Brecht Morris gives instructions on safely taking scale samples at the first Predator Study Training Day

So how will anglers find out the results of the study ?

Each year the EA will produce an Annual Predator Study report which will give anglers an easy to understand overview of the results of the study. These results will include growth rates on the different rivers and different sections of the river, mortality rates, information about fish movements and catch per unit effort information. It is also hoped that if the study runs successfully for a number of years then funding can be found for a PHD study of the results which could include stable isotope analysis which would even indicate the preferred prey species of each pike caught. Not only will all this information be of great interest and value to predator anglers, but the growth rate information in particular will become a baseline to compare future years results as an indicator of the health of general fish stocks on the river. Where the predator growth rates rise and fall will tell us where the overall biomass of fish is rising or falling.

Dilip has a go at taking scale samples.

Dilip has a go at taking scale samples.

So how do I get involved ?

This project provides an amazing chance for anglers of all abilities to be part of an ongoing scientific study of the fish in our rivers. We have already held our first training day which was great fun and well attended and we will be holding our next training day in September. So if you’d like to know more or want to attend the next training session just drop us an email and we will give you all the details.

john.cheyne@anglingtrust.net

The Predator Study Kit that each trained volunteer will receive.

The Predator Study Kit that each trained volunteer will receive.

 

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