Maybe it has been so because there was nothing to buy or use to find fish except the anglers brain and his experience. Now it is true that you cannot put watercraft in a bottle but if you take a look at the overall fishing tackle there is such a product which can at least help you to develop your watercraft, the echo sounder.

In the States it is called a FishFinder but it's exact role is more like a "swim-finder" or a "feature-finder than a fish locator. So let's refer to it as an echo-sounder which is what it's technology is based upon. Of course there is a lot going on about the ethics of using such equipment. Is it fair to the fish, what chances has it got? And so on. First an echo-sounder is no good if you are not an angler and it will not make the carp jump into the sack with a label indicating their weight. I think that we all want to catch fish and we like to use the modern technology available in order to make the best out of our hobby time, the echo-sounder is just another part of our armoury just like a rod and a reel. Furthermore it now costs just the same as a quality rod and reel combination.

So let's have a closer look at the "sounder" and what it can give to carp fishermen. The sounder which interests us is the one designed for sportfishing. It's small, portable and waterproof unit, made of a liquid crystal screen, a battery pack which usually supports the screen and the last but vital part of the machine, the transducer which is linked to the screen by a cable.

How does it work? The principle is the sonar technology: The transducer sits in the water usually at the back of the boat. In the water it transmits a sound wave down to the bottom which reflects it back to the transducer. It acts like a transmitter and a receiver, because speed of sound in the water is known, the distance travelled by the echo can be calculated to give us the depth.

The bottom profile is drawn on the screen section by section, corresponding to each individual depth. When it appears on the screen it is already history of the area just covered, as the scrolling is continuous even when the boat is static. This is because signals are transmitted from 10 to 12 times per second.

Fish are shown because they also send back their own back signal within the main back signal earlier and before the bottom. They usually display as inverted arches when not in fish identification mode.

The transducer is the most important part of the echo-sounder, it's installation is critical. Always refer to the owner's manual for a correct fitting, otherwise the reading will be altered and the information wrong.

From the specification of the transducer (frequency and cone angle) depends the coverage. The sound is propagated in the water from the transducer very much like the beam of a torch light, it is called the cone angle. When hitting the bottom area covered is like a circular footprint, with the standard transducer of an Eagle Echo-Sounder. For example, the cone angle is 20 degrees, the area covered has a diameter roughly equal to one third of the depth. In 30 feet of water the circle has a diameter of 3 feet. It may seem small but it all comes down to finding the best combination. Just like a torch light, a wide beam does illuminate a lot. At a shorter distance, a narrow beam would go further but will illuminate less surface. This is why a cone angle of 20 degrees and a frequency of 192 KHZ ( the number of pulses per micro second) offer the best combination for shallow to medium depths i.e. 0 to 120 meters. The frequency also dictates the echo-sounders performance. The higher it is the greater the resolution will be but the lesser the water penetration will be. A low frequency will go deeper but will show off less details. For freshwater use and for carp fishing a 20 degrees / 192 KHZ transducer gives the right combination between covered surface and detailed resolution. Carp fishing never exceeds depth of more than 50 meters even on the Continent, so there are no fears of not "locking onto the bottom".

Some of you may have found this technical section rather boring, but it is always nice to know some of the basic principles in order to use the product at it's best. The following will help you to use sportfishing echo-sounders to their correct potential and give you a few useful tips when looking for buying one. Before starting let us kill some preconceived ideas about sonar's. They are not video cameras, they do not catch the fish for you, they cannot tell you which species of fish you have found and they cannot tell you their weight, but they can give three important pieces of information. The first one is the exact depth to 10 cm. Then they will show the bottom profile and it's structure. Thirdly they will display fish individually or as shoals.

Getting a view of the bottom and knowing it's structure is of prime importance to select a baiting area, to identify a fish, holding structures, locating snags, determining silt from gravel and to quantify the height of weeds or even to mark a thermocline. Finding a gravel bar becomes really easy as well as gullies, plateau's, drop-offs, rocks and tree stumps. To make your searching even more accurate do not hesitate to draw a map of the areas you are sounding. Drop markers on top of each of the interesting features you have detected, and come back to it from different angles to get the best possible picture of the areas.

Most Eagle units have a function called "Grayline". It is an indicator of the bottom hardness which also helps to separate structures or targets from the bottom itself. Just above the dark line figuring the bottom profile a grey zone is displayed, if the bottom is of hard consistency the Grayline will be wide. If the bottom is silty or weedy then the Grayline will be thin. This is because the Grayline works against the strength of the return signal bouncing off the bottom. Hard grounds give a stronger back signal than soft grounds. Just like in the air if you throw a tennis ball against a wall it comes back to you quickly and strongly, against a curtain it does not reach you with the same power. Also if you get a secondary Echo on the screen it indicates a hard bottom consistency. Weed will typically show as a black layer above a thin Grayline, it may extend right up to the top in shallow water.

What about carp, are there any chances to spot them? Carp usually give a strong back signal and often show very well on the screen. First they are slow moving fish, then they have a wide back for the echo to reflect upon and a big swim bladder which contains a lot of air. Fish with big swim bladders give very positive signals as the air stops the sound travelling down the water. Now it is not possible to recognise 100% that carp are on the display but when you locate several large fish just over the bottom, chances are that you have probably found some carp. Except for catfish you do not find large fish in shoals in our freshwater. A shoal of small roach will appear as a black cloud suspended in mid water. In fish identification mode fish are shown as fish symbols of 3 or 4 different sizes. In this mode the unit recognises the back echo for a fish and shows it as a fish symbol. However the fishfinder has some limitations. When several small fish are swimming close together, the 'fish in' mode can mistaken them as one single fish. This is why it is advisable when looking for carp to start with the 'fish in' mode on and turn it off as soon as you begin seeing fish. Once turned off 'fish in' will leave inverted arches for fish. The bigger and thicker the arch, the bigger the carp! A decent sized carp over twenty pounds will also show a layer of Grayline in the arch. Again it means that the signal coming back from that target is very clear and strong. But always remember that in shallow water a small fish gives a stronger return signal than in deeper water. So if you are in your boat in one meter of water a double will look huge but in 15 or 20 meters it will only show as a medium

Locating carp is useful when trying to establish the feeding zone depth in large deep waters. If you locate carp in say 5 meters in several spots you may be advised to put your bait where the bottom reaches this depth. Also once you have chosen your baiting area and started baiting up, if you want to check the presence of fish over the boilies, it is a good thing to let your boat drift quietly over the markers and read the screen. When the carp are static in winter, finding them can be the key to success and the sonar can help, although a static fish lying on the ground is much harder to detect than a moving one. In this case use the zoom to get an enhanced view and watch the Grayline indication which will separate independent echoes from the ground, making interpretation more accurate. When first using your unit leave it in automatic mode before trying to adjust it yourself. To help anglers achieve better results, Eagle have developed an entire automatic mode called ASP (for Advanced Signal Processing) which constantly adjust the settings according to the water conditions, interference's and boat speed. The beauty of this system when searching for swims whilst carp fishing in shallow water, is that even in one meter of depth, the screen stays clear and the bottom profile highly detailed because unwanted echoes are the only adjustment you could make regards the sensitivity settings, although the ASP will monitor that for you. As a rule of thumb decrease the sensitivity in shallow water and increase it in deep water. Sensitivity does not affect the power output but the amount of information displayed. To get a view of a thermocline, you would need to increase the sensitivity until it starts to show on the screen. Thermoclines are found in big deep waters often in the winter, and can well aid location.

Before thinking of buying an echo-sounder, first make sure you have a decent boat for safety reasons and also because you will find that you will spend a lot of time in the boat surveying the water.

So which echo-sounder should the carp angler be using?. The most important function is the Grayline, it is a must to understand the water and make correct interpretation. Then you will need a large screen with a lot of pixels (a 100 minimum-128 being better) for an enhanced resolution. Choice of power is not as critical as in deep sea fishing. 275 to 600 watts is more than enough for general freshwater use, especially for carp fishing.

Transducer specification such as the standard Eagle Skimmer 192 KHZ/20 degrees transducer is perfect and offers an excellent balance between coverage and details resolution. Those are the specifications you should be looking for. Units like the Eagle Magne 3 are the most popular amongst European carp fishermen. Just think of the time you can save on a trip to France for example. In just one day you can gain knowledge it would take years to learn, in this sense it is a revolution and this is where the
future of carp fishing lies. Being able to determine where the carp should be feeding.

THERMOCLINE SLIDE A
Note how consistent the thermocline is and how it extends above the ground. Areas of the bottom in contact with the thermocline are best suited for establishing a baited zone. Note the Grayline variation indicating bottom structure.

LARGE CARP SLIDE B
The zoom allows you to spot a very large carp just above the bottom in a deep French reservoir of central France. The amount of Grayline within the fish indicates the strength of the back signal (Eagle Ultra 111). Note the split-screen function which displays the normal view and the zoom area at the same time. The box on the left displays the depth and the surface temperature.

SHALLOW WATER OPERATION SLIDE C
The bottom profile is still highly detailed and the screen uncluttered. Under such conditions the ASP gives the edge over conventional echo-sounders.

A MODERN SPORTFISHING ECHO SOUNDER SLIDE D
The Eagle Ultra 3 is currently the best unit for carp anglers. It also has a function called the Broadview which allows you to sound simultaneously left and right from the side of the boat for even greater depth fish location. The screen is displaying a depth of 10.8 meters and a weedbed at the bottom of a slope. Note The fish suspended above it.

by Bertrand Picard