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Swordfish, Tunas and the Moon
by:: Edward R. Gaw
PRINTED:: Fishing Boat World: May 1998

Howl at the moon - not if you are fishing for swordfish and tunas. Second only to local weather conditions, the moon represents the most significant influence in the long-line capture of swordfish and tunas. Improvements in long-line gear and materials have been closely shadowed by refinements in long-line techniques and applications. Successful fishing and adjustments are effective because they control key variables and take advantage of specific peculiar traits of swordfish and tunas. The idea that large pelagic fish do not feed randomly throughout the day and concentrate their feeding activity to specific periods requires an understanding of the lunar phases and their effects. This article will describe this lunar influence and its importance in the vertical placement of monofilament long-line gear.

As with all fishing, the development and evolution of monofilament long-line gear is a work in progress. Constant improvement of long-line gear and materials is coupled with experimentation and produces improved applications by fishermen. In its simplest terms, it remains every long-line fisherman�s goal to maximize gear over-lap with the vertical and horizontal distribution of swordfish and tunas. Monofilament long-line gear has proven successful in covering the full extent of the horizontal distribution of swordfish and tunas. However, given the structural limitations of monofilament gear and the extended vertical range of these target species, the area of vertical gear over-lap is limited. Once a horizontal determination of a concentration of fish has been made (selection of a fishing ground), calculated vertical gear adjustments may significantly improve catch rates. An appreciation of the power of the moon on the effectiveness of monofilament long-line gear will determine the best gear construction, fishing depth and soak times. God can be found in the details and genius of interpreting long-line gear soak times and lunar illumination. In the determination of successful fishing strategies and calculated local adjustment - the moon figures heavily.

It is the design of monofilament long-line gear to capture actively feeding swordfish and tunas. These species are contrast feeders drawn to water that collect concentrations of prey items. The retina of swordfish and tunas are packed with specialized �rods�, sensitive to short wavelength light, necessary for keen low light vision. The fact that the light gathering ability of the eye increases with the square of the pupil�s diameter makes swordfish and tunas extremely sensitive light gatherers. The ability to artificially concentrate bait is an effective measure of any long-line gear. Local lunar influence on the concentration and location of bait allows strategically placed gear to magnify local bait concentrations. The activity around and through your gear resulting from higher bait concentrations significantly increases the probability of encounter and capture. If it is true that you are better fishing water that collects concentrations of bait, then the influence of the moon makes a determination of appropriate bait depth easier.

Primarily all bait species are diurnal in nature, staying deep during daylight and rising to shallower waters as light diminishes. This daily migration can be witnessed on any standard sounder, sonar or depth recorder. Reflected light from the moon penetrates the water and influences the vertical placement and density of this bait, or �scattering� layer. This lunar effect increases as available light increases toward the full moon. The moon�s effect on nighttime long-line fishing begins with the first quarter and trails with the last quarter because the � moon phases peak in the sky during low light periods of sunrise and sunset. From the first quarter through the last quarter, reflected moonlight creates a ceiling above which bait will not rise and around which bait concentrates.

Consistent with most orbits, the path of the moon around the earth is an ellipse, with the closest point, perigee and the farthest approach, apogee. Increased gravitational force on the Earth at perigee can lead to higher high tides and lower low tides than normal. When the moon and sun are aligned with the Earth (new and full moon), the moon�s tidal effect couples with the sun�s gravitational force and significantly increases tides. The moon has a synchronous rotation resulting in one full rotation in the same time required to orbit the Earth. It takes 29.5 days for the moon to complete a lunar month, new moon to new moon. This combination of factors causes the moon to rise and set at different times each day of the lunar month. Every twenty-four (24) hours (one complete Earth rotation) the moon has precessed 12 degrees in its orbit (eastward). This movement results in moonrise times 51 minutes later each day. Sunset and moon rise times combine to trigger bait movements 51 minutes later each day. In addition to successively later moonrise times, the moon�s height above the horizon changes from season to season. In the northern hemisphere:: In early spring the moon�s first quarter is the highest, the last quarter the lowest, with the new and full moons rising to the sun�s mid-day high point; In winter the full moon is the highest, the new moon lowest, and the quarter phases rise in-between. Determination of the amount of local moonlight available resulting from the moon�s seasonal position and daily moon rise times influences the after dark impact of lunar illumination on drifting pelagic long-line gear. The best captains and successful long-line vessels adjust their gear and technique over the course of a fishing trip. The successes of each set reveal details about fish feeding behavior and gear interaction. Collection and incorporation of these clues separates the good, from the bad, from the ugly. It should be every long-line fisherman�s focus to coordinate after-dark moon light with vertical gear placement, soak time and gear construction - primarily depth and light-stick quality. The key to this style of fishing is - INTERCEPTION. Each set should be an attempt to maximize gear over-lap with swordfish and tuna movement between deeper travel depths and shallower feeding zones. Simple review and calculation of moonrise, sunset and sunrise times affect the adjustment of setting and hauling times. Local conditions of cloud cover and sea state will influence the location of the bait �scattering� layer and determine how deep swordfish and tuna baits should be fished. Probably the best indication of proper depth adjustment is evidenced during haul-back. Retrieved baits that are chewed or molested by smaller baitfishes are a positive sign and provide strong indication that your baited hooks are at the level bait is holding.

The interaction of the formation of this layer and its movement relative to the construction, sweep and soak time determines fishing success. The employment of colored light-sticks on pelagic long-line gear targeting swordfish and tunas should be coordinated with this lunar bait effect. Color selection, light output and attachment position of light-sticks on the gear should be adjusted according to differential light levels associated with each moon phase. Light-sticks significantly increase the fishing power of swordfish and tuna long-line gear. The ability of a light-stick to generate contrast motivates the use of a larger 6� light with predictable burn qualities. Higher fill volumes of light producing chemical in 6� lights produces a more consistent and predictable burn and allows for accurate placement and higher catch rates.

The use of light-sticks to exaggerate and intensify the collection of bait through active gear requires some thought. During full moon periods, because of the increased amount of reflected light penetrating the water column, the effectiveness of shallower set light-sticks may be diminished. It is during these periods that a larger, brighter light-stick is required to produce the same bait gathering ability during lower lunar light periods. Conversely the re-use of 6� light-sticks, with higher chemical volumes, a second night, at a lower intensity, has proven effective during lower lunar light periods. Because most light-sticks are at 50% their original intensity one hour after activation, light-stick placement on the leader can significantly affect gear efficiency and performance. The extinction of light from a light-stick, its distance from the hook and the timing of the bite, (late bite or early bite) will move the light-stick closer to or farther from the hooked bait. Each light-stick color has its own unique burn curve and spectral qualities characterized by a combination of initial brightness, burn duration and water penetration. The correct distance from the hook for light-stick attachment is that measure which causes the hooked bait to fall just outside the greatest influence of light, or the light-stick �shadow� zone. The shrinking zone of light created by the light-stick and its location on the leader should be timed with the highest period of feeding activity, as evidenced from previous set experience. Consideration of these properties enables each fisherman to calculate and intelligently select the most appropriate light-stick color, or colors, for any fishing conditions. Early set success and experimentation are the best guide to local gear refinement and adjustment.

Successful long-lining comes from a basic understanding of the interaction of many different variables. The importance of these factors vary but the moon and its phases strongly influence the location and abundance of food items in time and space. Because the prey species of swordfish and tuna are creatures of the edge, it is possible to improve the placement of pelagic long-line gear within a fishing area. Vertical limitations of monofilament long-line gear demands constant refinement of gear construction and materials. Patterning fish behavior by scouting a particular location with different gear parameters allows refinement over the course of a fishing trip. However, it remains crucial to remember that a lack of initial success in the adjustment of any gear component does not equal failure. It is strongly recommended to incorporate some degree of gear variability in each set made. A reasoned approach to after dark lunar illumination will improve any vessel�s catch history. A more detailed explanation of the moon and its influence on pelagic monofilament long-line gear use can be found in; LONG- LINE FISHING FOR BIG FISH, by Walter Flanagan and Edward R. Gaw.
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