I promised to write something on bluewater fishing deep structure. Now I have started it, I think I’m going to have to split it into parts. There may be a book in the making here! I intend to illustrate these articles with real shots of on board electronics and fishing conditions, but I don’t yet have all the shots I need. Watch this space!
If you think of anything I missed, or you have questions, ask me on the thread and I will try to answer. There is no right and wrong way to fish. This is just my way.
Fishing deep structure
Whether you fish from your own boat, or from someone else?s, or you charter a vessel to fish from, a quality colour depth sounder and a GPS with a plotter function that can mark waypoints with various symbols and record your track in graphical form are two essential tools which I would not want to fish without. Modern electronics are fantastic aids to fishing, helping find structure that holds fish, helping you see and identify what fish may be there and helping you choose the best methods to target the fish you see. These same electronics will help you get back to the same spot, time after time with pinpoint accuracy. What you see there each trip may be quite different from what you saw last time and your electronics will again help you interpret how best to fish in changing conditions.
Your sounder and GPS combination will also have additional features such as speed and water temperature that can help you. Used in combination with your eyes, nose and some degree of imagination and thought, you have a deadly combination of fish finding tools at your disposal.
Here?s how I use my electronics in combination with sharp eyes to recognize fishing opportunity over structure and how I go about fishing the structure given the interpretation of what I?m looking at.
Part 1: Finding structure
Hard Structure
You may have been given co-ordinates to a good piece of hard bottom structure by someone else who has been there, you may have seen an interesting piece of structure on a map and decide it?s worth investigating or you may just stumble across structure while you are trolling or traveling from one place to another. The first two situations involve plugging in the co-ordinates into your GPS and simply going to those co-ordinates.
The last situation is why I always have my depth sounder switched on when I?m cruising from one spot to another. I may pick up a bottom feature that I have not seen before. It may or may not have fish on it, but I mark it. The structure may be bigger than you expect and it may actually hold lots of fish when you take the time to investigate. Once marked with a single waypoint, I can now drive to that spot and find it anytime I feel like.
In shallower areas or when you?re fishing the shelf, you?ll be looking for hard structure much of the time. These are obvious features that stick up from the seabed and are easy to find with a depth sounder. We?ll deal with mapping them out and fishing these structures a bit later.
Soft Structure
In deep water or off the shelf edge, there is lots and lots of empty water. It can be quite disheartening to fish miles and miles of water that all looks the same. You need something on which to focus your fishing efforts. You are looking for differences, edges and areas where currents might be deflected that are often difficult to pinpoint, so don?t forget the visual clues that can lead to both fish and structure. Good fishermen are constantly scanning the water. Birds working are a good indicator of fish, as are the splashes of feeding fish, but there are other clues. Flying fish and dolphins can often lead you to fish. Spinner dolphins are a small species of dolphin quite common in Ujung Kulon. They travel in family groups or huge pods, sometimes with hundreds of individuals. They can be spotted from long distances because of their habit of jumping and spinning. They are commonly found traveling with schools of tuna, most often Yellowfin Tuna.
How to interpret their behaviour and that of the birds that are usually with them to help you locate the tuna is a different subject, but we?re interested in these clues if you notice that on successive trips, the activity is always around the same spot. This can also lead you to structure.
Other, more subtle indicators of structure or fish can be tide lines with floating debris along a current edge. This may be associated with a colour change from green water to blue or maybe just a very subtle change in shade. This is structure, just as much as a reef on the bottom. Soft structure can be as productive as hard structure. If you cross the line and there is a change in temperature from one side to the other, it?s worth fishing. A temperature change of half a degree is worth fishing. If it?s a few degrees, you might be in for a good session, depending upon where it lies. Your depth sounder will probably have a temperature chart feature where you can plot up temperature along your track. Use it. Get into the habit of checking it from time to time. If you identify a temperature break, you?ll want the temperature plot up on a split screen to use with the sounder or the GPS track plotter function. These features are often transient and temporary. Fish them. Where they occur over hard bottom structure, they are particularly interesting. When they lie over deep underwater drop-offs or canyons, reefs and rocky bottom they are your invisible indicator to concentrations of pelagic fish.
Another indicator of deep structure is different looking water. It may be a patch of water that ripples in a slightly different way or is smooth or swirls or any number of subtle little differences. It may stand out by being much rougher than the nearby water, like a tide rip. Commonly, where there is bait in the water under the surface causing it to ripple, it?s often referred to as ?nervous water?, but I think this is a perfect description for the visual clues of deep underwater structure you are looking for.
The actual bottom structure that causes these effects in the water may be some distance away from where they are visible on the surface. It may take a determined search to actually find the hard structure. The deeper the water, the further away it might be. In deep water, you?ll be trolling the upper disturbed layers anyway, not the bottom feature causing them. The disturbed area may not always be down current, although you will see some disturbance on this side when the features are shallow. In fact, in deeper water, along drop-offs, the current creates a pressure wave on the up current side of the structure and its this pressure wave and associated upwelling where we will find most of our fish.
In Ujung Kulon, the ocean current often runs parallel to the drop-off and there is no upwelling to create soft structure worth fishing. But where the drop-off is bisected by deep canyons that cut back into the shelf, the current might get deflected here in a very small area. The water might be 600ft or 1000ft deep, but the waters surface has a different appearance. The area may be very small in a huge ocean, but these spots are very important to recognize.
I?ll give you an example of how important this can be. I fished a week aboard Tim Dean?s 40ft Black Watch Calypso with Captain Steve Tedesco on the GBR out of Cairns one October a few years back. It was the height of an excellent heavy tackle Black Marlin season. Boats were scattered up and down the reef for over a hundred miles, but the bulk of the fish were taken in very small areas each day. I asked Steve about this as we trolled north from Cairns and he told me the current was running parallel to the reef and had been for several weeks. I knew immediately what he was looking for and pinpointed some areas on his GPS map chart and asked if this was where the fish had been caught. These were areas where I could see the reef turned slightly and gave the correct geometry to deflect the current and cause upwelling. To cut a long story short, we spent the bulk of the charter fishing one of these curves on the reef, an area not much bigger than a football field out of a hundred miles of possible fishing spots. Results were excellent and I could see the difference in this patch of water we fished compared to the rest of the reef. Some boats outside this small area caught little or nothing. Boats that got inside it were getting fish.
Mark these spots on your GPS for future reference. You may not at first realize why the area is different but as you become more familiar with the area, currents and structure, it will start to add up to a predictable pattern.
If you look at a map of Ujung Kulon on the SW tip of Java, the Indian Ocean meets the Java Strait right at Ujung Kulon and currents usually flow from north to south in the straits. Warm water at 82 degrees F from the shallow Java Sea pours into the Indian Ocean at 2 knots and creates a temperature break, tide rip and often a colour change. Depending upon the season, the Indian Ocean may be at 78 to 80 degrees F creating a 4 to 6 degree temperature break that is like a brick wall to a baitfish. The associated tide rip runs out to sea, perpendicular to the coast at Ujung Kulon, so you can troll the tide rip and temperature break from shallow to deep, over the drop-off and back again. The break is quite visible when you know what to look for. It will be a band of rough water with much larger waves than the surrounding sea, and this corridor may be 100 yards wide. The Indian Ocean will be blue and the water from the Sunda Strait will be slightly greener. Your temperature plot will show you the break. I have seen boats avoid this tide rip and fish around it, because the surrounding water is much calmer!
When conditions are good, it?s time to get out the skirted lures and set out a pattern for Marlin. I can almost guarantee there will be feeding Marlin under those conditions and we?ve tagged and released triples in an hour with double headers not unknown. You?ll also encounter Sailfish, Wahoo, Yellowfin Tuna, Barracuda and Mahi Mahi hunting the same water. Given that we frequently see Marlin tailing down the swells in these conditions, it can be an adrenaline charged experience. The productive band of water may be no more than 100 yards wide and 1 mile out and back across the drop-off. Use your track plotter set on 3 mile range to monitor the ground you cover and take note of the water depth you get your strikes. The fish will always be traveling down sea, parallel to the shoreline and will usually be in the same depth band, either on the shelf, at the edge or sometimes in the deeper water. The tide rip will be perpendicular to the direction the fish are traveling in, which is perfect because by staying in the rip, you?ll cross the path of many more fish as you?ll be trolling across their track.
Similar conditions may exist many miles out to sea at the mouths of big rivers and these areas are often rich in bait. These areas are particularly attractive to Sailfish.
Something else you may notice if you are alert is the smell of fish. I don?t mean like fish cooking in the kitchen at home, but I mean a distinct watermelon smell on the water. This is often associated with schools of baitfish or tuna. Oily slicks and a fish oil smell might mean feeding fish. Something has killed and eaten something else in this patch of water and you can smell it. When people say the skipper can smell fish, they may actually be right. He can!
The important thing here is, if it looks different, fish it. Mark it on the GPS for reference. In a new area, mark everything. Once you get familiar with an area, you?ll learn to recognize what?s important and what isn?t. This will help on return visits, but it will also help on one off trips because you?ll be fishing more selective areas and not just fishing blind. Concentrating your efforts where the fish are, or are likely to be, will always yield better results, often very much better results, so pay attention while you are trolling!
Part 2: Mapping structure and building a mental 3D picture
Part 3: Finding the fish on structure
Part 4: Interpreting fish and their behaviour from your sounder
Part 5: Trolling structure
Part 6: Jigging structure
Thomas 
