The advances in fish-finding equipment are mind-boggling.

I was fishing off Gisborne last week and one of the spots we sometimes swing by is called Fluke Rock. Named, presumably, because, well, someone once fluked it without any of the fancy modern-day technology that is now so readily available.

Now, I'm well aware that an article about recreational-boat electronics risks landing dryer than a Gisborne chardonnay. But an arms race has developed between manufacturers in recent years that is staggering in its advance.

Winding back a few decades, I have vivid childhood memories of staring at my uncle's fancy depth sounder (fish finder). We were only allowed to turn it on when we were sure we were at the spot, as the scratches of the flicking arm were recorded on special paper of which he had a finite supply.

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I marvelled at how it showed depth and the faint ghostings of fish being recorded as lines and scratches from many metres below us. Global positioning wasn't available then, so spots were found by lining up landmarks and driving boats along compass readings, with a bit of good old-fashioned guesswork.

Fast-forward to today and I have a GPS map-reading app on my phone and even kayaks have depth sounders.

Now I want to unpack this one step further, so please bear with me here as it gets a bit nerdy.

The "transducer" is the bit that hangs off either the back of the boat or goes through the hull to send its sonar pings down to the bottom. These signals are interpreted by your screen to provide a picture of what is bouncing back up. The signals can't pass through air, so a fish's air bladder effectively allows us the ability to see them. Spend time with your sounder and you can even tell species apart. Fishers who know will know what I mean when I talk about "snapper arches" and "kingfish squiggles".

Anyway, most transducers beam out at two frequencies in a cone-like shape, 50MHz (wide cone) and 200MHz (narrow cone).

Or at least they did. In the past few years things have heated right up as manufacturers have taken full advantage of new technologies.

Take a transducer's strength for example, which is registered in watts (RMS). Early versions offered came with just 38RMS. Today there are trailer boats that have dual transducers pumping out at a staggering 3kW each. This allows them to read deep water in incredible detail.

The depth-sounder records bottom contours as you go so you can create maps of your favourite spots.
The depth-sounder records bottom contours as you go so you can create maps of your favourite spots.

But it doesn't end there. Traditional echo sounders are now giving way to new systems like CHIRP, which pump out a range of frequencies all at once to allow for targeted separation and for more defined pictures to be developed. There are now units that can scan sideways to literally see fish around you, not just underneath. New units are so good that individual fish can be tracked hundreds of metres below.

But wait, there's more. Take marine electronic company Garmin, who in 2016 launched the first recreational in-built mapping system, able to redraw the bottom in real time.

Called quickdraw, it works with your GPS co-ordinates to paint and record a detailed picture as you boat about. After a while, you end up with your own personalised set of bathymetric maps which develop in more detail the more time you spend on the water. It even has a function to allow you to share your maps with others online — but no real fisher would ever give away such precious state secrets.

Though commercial boats have had these functions for years, the pace at which the recreational market is catching up is phenomenal as new processing powers are harnessed.

Mind you, none of the top end of this is cheap, so if your partner has recently quietly updated their vessel you might want to make inquiries, as some trailer boats are now known to have more than $40,000 worth of kit fitted. I wonder how much special paper that would have bought for my uncle's old unit, now just a distant relic in this technological march forward.

Clarke Gayford hosts Fish of the Day.