Fishing with Technology
Blending electronics know-how with natural angling instinct can give your team a leg up on tournament day.
The old saying in fishing is “you can’t catch what’s not there.” And when people ask me for one piece of angling advice regarding fishfinding, my response is “fish where the fish are.” When heading offshore, one of the most difficult decisions I make as a professional charter captain onboard the 60-foot Canyon Runner is where to drop lines. Modern electronics provide a wealth of information right at the helm, and smart captains know how to use this information to put fish in the boat. Here are a few technology tips to turn the tide in your favor.
The chartplotter helps me find the intersection of great bottom structure and temperature and/or color changes in water. First, I must be sure there are bathymetric charts loaded into my machine and that there is a satellite feed of sea surface temperatures (SSTs). The bathymetric charts are available from Navionics or C-Map, and the satellite feeds generally come from Sirius or XM. Your particular brand and model of chartplotter determines which company’s charts and feeds you’ll use.
The bathymetric charts show the ocean bottom in much greater detail than standard navigational charts. Whereas a navigational chart shows contours in ten-fathom increments out to 100 fathoms then 500 and 1,000 fathoms, bathymetric charts show contours in increments of 25 feet or less. By having more detail, I can easily find contour lines that are very close together and display a rapid change of depth or a very steep slope (structure). Bait and game fish tend to congregate in these areas. Great bottom structure is the first part of the puzzle, but it must be combined with the correct water temperature and clarity for the type of fish being targeted. For example, when I chase yellowfin tuna in the Northeast canyons, I am typically looking for clean blue or blue-green water from 68F to 76F. My plotter’s satellite temperature feed not only gives me water temperature but will overlay that data onto my bathymetric chart. This makes finding the intersection of the favorable water temperature and good bottom structure and depth very easy.
Once I’ve found promising water, my boat’s fishfinder tells me what’s going on underneath the surface.
The fishfinder works by shooting a signal into the water and receiving that signal back after bouncing off an object such as fish or the bottom. The strength of the signal returned to the fishfinder is determined by the size and density of the object it pinged. Typically, the strongest signals will show as red on your screen and the weakest as blue or green. Using this information, you can determine what type of fish or bait is on the screen. Large fish will show as individual red marks. Dense schools of bait will show as large masses of red while scattered bait will show as speckled blue/green patterns. By using this information and noting the correlation between marks on the fishfinder and catches of game fish or bait, you can get proficient at interpreting what a fishfinder is telling you.
In order see below your boat accurately, the fishfinder must be properly setup and tuned. To do this, I start by turning off any noise or clutter reduction. Next, I reduce the gain to zero. With the boat drifting or at slow speed, I set its depth range to 2.5 times the water depth. For instance, if I’m in 100 feet of water I set the depth range to 250 feet. Slowly the gain setting is increased until I pick up the bottom at 100 feet. I continue increasing the gain until there’s a faint repeat image of the bottom again at 200 feet. At this point, the gain is set, and I’ll see a bottom at 100 feet and a secondary image of the bottom at 200 feet. There will likely be clutter on screen so noise reduction can be increased until weak signals are filtered out. If I’m looking for the thermocline, which is the depth where there’s a rapid change in water temperature defining a warm and a cool side, the clutter reduction will have to stay at a minimum and gain will be increased above the baseline to show the change in water density at the thermocline. This method of setting the gain works at any frequency. Speaking of frequency, I typically use 200 kHz in water less than 400 feet and 50 kHz in water deeper than 400 feet. One benefit of using 50 kHz is that the beam angle is much wider then 200 kHz, so fish that are not directly under the boat can still be seen.
Another trick that helps pick out fish in deep water on the display is to split the screen in half with separate depths. On Canyon Runner, I set the right side of the screen to the depth of the bottom and the left side to 200 feet. With this setup, I can see bottom ledges or slopes and bait holding deep on the right and still have a close-up image of the targeted water column on the left.
Radar is helpful when looking offshore for congregations of boats or birds. While finding a concentration of boats may seem like finding a pot of gold (or fish) at the end of the rainbow, it doesn’t always work out that way. For some of us, finding the boats and fishing away from them is a top priority. Many times fish are less spooked where there are fewer boats.
When looking for birds by radar, I usually extended the unit’s range out six or eight miles with the gain increased above baseline for navigation, and sea and rain clutter turned down to minimum. This will cause some random on-screen clutter, but consistent areas or concentrations of clutter are often birds gathering over feeding fish.
Advancements made in marine electronics over the past decade are readily available and affordable to most anglers. By combining today’s technology with old-fashioned skill, and watching for those telltale “fish are here” signs when headed for blue water, you can give your crew the edge that can fill your fishbox and put your team on the leaderboard.
This article originally appeared in the April 2011 issue of Power & Motoryacht magazine.