Groundfish Longliners

Go right to the images?

Set longline - Groundfish	Haul longline - Groundfish

or, you can open them later as you go through the text below.

You want to know about the bottom in the area you are going to fish, to make good decisions as to where to shoot the line.  Hit and miss setting between marks on a conventional plotter, or following a depth contour isn't going to make the most effective set.  Below is a description and screens from a Marimsys BRIDGE set.

A few miles west of the fishing area, the main flow of the cold and powerful Humboldt Current goes by, South to North.  Where we are fishing is in the zone of the inshore eddies.  These sunken river valleys, part of the Chilean Continental Shelf were gouged-out back in the time of the glaciers, and are now hundreds of meters below the ocean surface.  The high ridges surrounding the valleys push the current up into mini-upwellings which slows the water flow and causes sediments fall out into the valleys.  To confuse the issue, current flows east up the valleys from the Humboldt Current.  The force of this incoming current can bare the rocks at the narrow points, or where the valley makes abrupt turns.  At the tops of the ridges jutting up into the currents, there will be almost bare (and jagged) rock. 

To fish those jutting bare ridges, you'd want much more detail; change to another Marimsys Chart made of that specific area - with 1 or 2 meter contours (not shown). 

Here in the valley shown, you want to fish the zones where the sediments fall out, the bottoms and the sides of the valleys.  This chart enables you to see the valley sides, to estimate the effects of a generally SW current and work out where to set.   The set is along the valley side, about 4 miles in length, and within the target species range between 450 and 750 meters.  The red down arrows are the buoy locations.  Click on the Set Longline - Groundfish image below to see it.

 
Set Longline - Groundfish

For the haul you'll want to retrace just the track segment you saved while shooting, saved as the red heavy line.  Knowing where and in what conditions you caught fish will help plan the next set.  You will click in a catch entry for every 10 fish coming in over the side and see how the catch compares to the terrain.

A bit of explanation about the screen:  the upper left status bar gives cursor position, the bearing from the ship to the cursor, and vessel speed.  The status bar along the bottom tells you that instrument data is entering, ship position, time, date, course, vessel speed, echosounder depth, temperature and the status of the Autolog.  The ship position is represented by an arrow, and right below the tip of the arrow, you'll see the depth shown for the position on the Marimsys Chart - 488 meters - same as the echosounder. 

After the haul you'll want to see on what types of bottom you fished best, and where you didn't do so well, and to figure out why.  The haul image displays the haul points (green up arrows) connected as a route (with a red heavy line).  You also see the shoot points (red heavy down pointing arrows).   With them side by side, you look at the icons, assume that the line rested on the bottom close to the midpoint, and you can estimate current drift while setting.  Or if you prefer, you can measure the distance between the marks and hence the drift with a right button click.  

This icon on the image    shows a catch entry, which in the actual program you could click to see the catch at that point.  We filled in a catch entry for every 10 fish coming over the side, so we would know where the catches were spaced along the line.  Click the catch icon     to see a sample report for 10 fish.

Now let's look at the actual haul.  Click on the small image below.

 
Haul Longline - Groundfish

Look at the catch entry icons group to the left of the image, what is different about that area from the rest of the line?  For starters, that is the deepest portion of the set, between 600 and 650 meters - looks like the fish may be biting at the deeper end of their range.  Also look at the spacing on those set / haul marks.  The set / haul marks to the west of the screen indicate little movement, but the greater separation between the marks at the East side of the valley, indicate that there is greater current there.  Looking at the image, this makes sense, the valley narrows, which would speed up current flow.  So it appears that there may be two factors driving the fish today - they like depths between 600 and 650 meters, and they like areas of lesser current coming up the valley.

The next set should be designed to clear up which variable is the most important - depth or current.  It appears that we should start out in the slow current area at the top of the species range, at 450 meters.  Then within a couple of hundred hooks, drop the line down into the payoff range from this set - to 600 - 650 meters.  Then continue the line on into the higher current area, holding to 625 meters +/-.

With this plan, we're going to learn if its' current or depth that's driving the fish today.  They may be biting out in the low current area at shallower depths - we don't know, haven't tried yet.  Then again, they may be holding to 600 - 650 meters regardless of the current, we don't know that either because we haven't tried that level of the high current area.

There's at least one more factor, we're now just past the full moon, and the currents are high.  Maybe the fish will stay out in the wide portion of the valley for the high currents, and move up into the neck of the valley in a week or so, hmmmm .....

With Marimsys BRIDGE and Marimsys Charts you have a view of the bottom.  You can visualize your fishing in front of that view of the bottom.  You will observe better fishing in some types of terrain, and not-so-good fishing in other types of bottom.  You will observe bottom that will catch your gear - and be able to fish right beside it, not on it.  You will spend more time fishing in the good areas, and less time in the others.  It adds up to more highly productive fishing days.

BRIDGE is a full-fledged electronic plotter that uses many different types of charting.  Notable among the types of charts it uses are Marimsys Charts, prepared by us from data gathered by your own vessel.  These provide a view of your workplace - the seabed - that is unsurpassed.  Scale can range down to about 1: 2500 for the difficult bottom where you need that level of detail to work.  Our Marimsys BRIDGE System gathers the data to make Marimsys Charts of the bottom, and also displays many different types of charts such as: Bathymetric, and Gravity charts for exploration of new areas; and of course, normal Sovereign Nautical Charts. 

These Marimsys Chart images are very highly detailed views of the bottom and provide extensive habitat information, as well as make the obstacles to fishing visible.  This means that you see the character of the ocean bottom where you are making (or not making) catches, and can  visualize the movement of currents and eddies over and around the terrain.   You can make connections over what combination of bottom type and feature (hill, valley, slope or flats) and current (ebb, set, various current layers, temperature, and season) are productive - and which combinations are not.  BRIDGE is a fishing system and is designed to help you answer the question: Why am I catching (or not catching) right-here right-now? 

F/V Friosur VIII and Captain Jon Ivar Halvarsson collected the data for these Marimsys Charts. Grimur Eiricksson and Carlos Vial I. kindly gave us permission to use these images, the property of Friosur S.A.  Our thanks to them and the Friosur team.  Latitudes and Longitudes appearing in the screens have been changed to protect the actual locations.