Wired for deep-sea soundings

Location scouting is now a high-tech business for the serious fisher, reports ROBIN BAILEY.

Gone Fishin! Two words that once conjured up lazy days with a rod or line, perhaps with a youngster in tow.

Today's dedicated fish-hunter is high-tech, with rods and reels available costing hundreds of dollars and a truly staggering range of traces, lures and hooks.

Then there are the electronics. Boating has been made much safer with the availability at affordable prices of simple-to-operate navigation aids. GPS plotters with built-in charts have added a new dimension to using paper charts, and compact radars with close-range capabilities are now finding a place in larger trailer boats.

However, it is the echo sounder/fish-finder that has made the biggest technological leap. Long gone are the days of the bulky paper sounder, where fish were indicated by a dark line on the paper and transducers were like great paperweights on the transom.

Fish-finders today are compact and highly sophisticated aids that not only give you the edge when fishing, but also accurately indicate the bottom shape and the terrain over which you are boating.

Deciding on the right type of fish-finder can be difficult. There is a huge range and many aspects of each unit to consider. You can pay as little as $350 for a black and white bracket-mounted sounder, or as much as $8000 for a full-colour unit that even includes a GPS/plotter.

So why do you need a fish-finder? Obviously to help to target the fish and define bottom shape. But there is no sense in buying a unit that will give an accurate 300m depth range if you do most of your fishing in the inner Hauraki Gulf.

For the average recreational fisher in the harbours and bays around New Zealand, anything over 50m is probably overkill.

For the more serious fisho, something that reads accurately to 100m may be the answer.

When making your choice, don't let yourself be convinced that the bigger the beam the better the sounder. That's not always the case. A transducer with a wide cone angle can find fish faster, but it may cover two or three important rock formations on the bottom and lump their reading together. A narrow cone zeroes in on fish and can detect small structure details - features fish may relate to.

Some types automatically manipulate receiver sensitivity and echo filtering to provide a wider coverage in shallow water and narrow, more detailed coverage in deeper water. Then add the advantage of multiple transducer beams that look to the side as well as straight down and it is easy to see where the fish are in relation to the boat.

The size of the screen is also important, and generally the larger the screen the easier it is to see important details. A large screen offers more room for side-finding displays, navigational displays and zoom functions without squashing the regular sonar view down until it becomes nearly useless. That's usually why combination units today, like the new breed of fish-finder/GPS/plotters, have larger screens to display all the information clearly.

Transducer type will depend on the type of boat. Most trailerboats have transom-mounted types and these are the most critical ones to get right. For launches, through-hull transducers are usually the best bet. The proper location depends on hull shape, and what works for one will not always suit another. A transducer must be placed where there is no turbulence to work effectively, especially at speed, and the signals won't travel through air bubbles.

There's a lot to consider. The latest issue of NZ Propeller magazine gets into the subject of fishing electronics in depth, comparing 60 units suitable for trailerboat recreational fishing.