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I am often asked: ” What is the best way to use your sounder to find the sonic scattering layer?”
The deep scattered layer is quite mobile , moving according to the time of day or night.
Late in the afternoon it can be seen rising from the bottom and migrating towards the surface layers. During the night it is within 50-200 fathoms of the surface and around full moon, it is condensed by the relatively high light levels at 30-50 fathoms. This is why swordfish fishing is more productive over the full moon period.
On dawn, it can be seen decending towards the bottom. Sometimes , it can be seen a a ribbon above the bottom and where it decends to the bottom, there are fish waiting.
You will only see this on powerful low frequency sounders – 3 Kw @ 28-38 Hkz.
Use your sounder on shift mode 0n 80-150 Fathom range and bottom lock.
Thanks for reply Jo.
Do you run your gain at highest level bascically cluttering up screen alot in order to find this layer or will it show up during your normal sounding for fish?
During the day will it only be in the bottom 150fathoms? When you say it’s seen as a ribbon above the bottom you follow that ribbon along it till it’s closer to the bottom is that right?
With bottom lock because it flattens out the bottom, do you find that you miss structure or do you you just use the bottom lock when searching for this layer and fish?
Thanks
Ken
Screen shot of 3 KW at 38 Khz in 255 fathoms on
bottom lock on daylight showing the deep scattered
layer descending towards the bottom. The red marks
at the bottom of the layer are a school of Blue Eye
Trevalla feeding on the descending layer. Caught
2.5 tons in 2 hrs.
Ken, the DSC wiil show up during normal soundings. I
have the sounder on 80 fathom range and shift it to
show the bottom in 300 fathoms. I have the gain on 5.The DSC will be around 250-350 fathoms during the
day and is concentrated around canyon walls and sea
mounts.
We often follow this layer onto the sea-mount and
fish at the depth that it touches. There are
usually fish feeding on it and we often get fish
with red shrimps, fang tooth dragons, light fish
and angler fish and long black eels in their mouths.I use a split screen to show normal and bottom lock.
The normal sounding shows the depth and structure
and confirms the 3D plotter image, and bottom lock
flattens out the bottom to show schools of fish
holding on very steep bottom.Thanks Jo that makes a lot of sense.
Do you find you get the blue eye, bass grouper and
hapuka at the same time or in different location?Do you always mark fish before dropping or do you
sometimes not mark fish and just drop on a structure
that you think looks good?Ken
Blue Eye and Bass groper are caught in similar depths although BG prefer rougher bottom.
Harpuka are higher up the slope.
Most of the time we fish marks. If I find some good structure without marks , it is always worth a shot. Sometimes the fish might be holding close to the bottom where they don’t show up and when you start catching them ,they burley themselves up into a school with all
the bait falling off the hooks and by emptying their stomachs when they get hooked. It doesn’t take long for a bit of excitement on the bottom to get something
happening.I understand that most of your fishing is done on seamounts way past the shelf. But if you were fishing on the shelf what kind of structure are you looking for the three species? As the shelf slope is exactly that just a slope out to the abyss till it hits canyons and sea mounts as my understanding.
Over summer when the EAC runs strongly down the
continental slope, I work wider out on the seamount
chain. The weather is also more stable and predictable
to be 180 nm off shore.In winter when the current slows down, I work the
shelf area. There are canyons all around the coast
and most occur offshore from major rivers. Canyons
are where ancient rivers cut through the Earth’s
crust in an past geological age. Sediment has
filled in most of the river bed inshore, but along
the slope, strong ocean currents prevent this.Along the 100 fathom line is also the remains of
ancient sea cliffs. Where sediment has not covered
them they exist today as a rocky terrace dropping
off to into deep water.On some parts of the coast, it is possible to
follow this terrace for many miles.With patience and good electronics, you can find
these areas. As it is mostly out of range of most fishermen, there are still good stocks of fish
there.Most recreational and even a lot of professional fisherman use 1kw or at most a 2kw transducer that don’t fish the distances you do. Some of these being tuneable to a frequency. Have you used a 1kw or 2kw for this fishing?
Are you able to pick up this deep scattered layer and/or fish with this size transducer?
I tried a dual frequency sounder with 3 Kw@38 Khz
and a tunable 82-88Khz.After using the both I just stuck with the 38 Khz
as with the 82-88 as the picture was not as good.I can get a bottom reading at 15 kts in 1200 fathoms
with my current sounder and fish life down to 800
fathoms. That’s good enough.In winter when you fish the shelf area. Do you just target canyons or have you located other spots on the shelf?
Canyons are a good place to start and as you get to
know the area, other features will be found. Any
small drop off or pinnacle will hold fish at some
time. I have 3D mapped 100’s miles of coast and
found most features with fish on them. The trick is
not to fish them too hard and give good producing
areas time to recover.
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