Purpose
Just as fisherman seek conditions where the chance of catching fish is optimized, fish seek areas where the chance of catching their food is optimal. Most game fish seek waters that are rich in food such as smaller fish, insects or shrimp. And, it follows, that these smaller fish, insects and shrimp congregate where their food is most concentrated.
Scientific research shows that all members of this food chain have eyes sensitive to the colors blue and green. This probably evolved because the water these animals live in is blue or greenish in color. Water, containing little particulate matter, scatters light in the blue region of the spectrum. If water is rich in nutrients and contains photosynthetic microorganisms and plants, the chlorophyll in their bodies preferentially absorb red light. The remaining, unabsorbed light is transmitted and scattered, thus giving the water a greenish appearance. If water contains a lot of organic material from decaying plant life or suspended sediment, it may take on a yellow-brown color.
Fish and some members of their food chain have color receptors in their eyes optimized for the light of their “space”. Eyes that can see a single space color can detect changes in light intensity. This is equivalent to a world in black, white and shades of gray. In this simplest level of visual information processing, an animal can recognize that something is different in its space—i.e., that there is food or a predator “over there”. Most animals living in a lighted world have an additional visual resource: color vision. By definition, that requires that they have color receptors containing at least two different visual pigments. To efficiently perform this function in water illuminated with light, an aquatic animal would have visual pigments sensitive to the background “space” color and one or more visual pigments offset from this blue-green region, say, in the red or ultraviolet region of the spectrum. This imparts a clear survival advantage to these animals because they can detect not only changes in light intensity but also contrasts in color. Many fish, for example, have two color receptors, one in the blue region of the spectra (425-490 nm) and the other in the near UV (320-380 nm). Insects and shrimp, members of the fish food chain, have blue, green (530 nm) and near UV receptors. In fact, some aquatic animals have up to ten different classes of visual pigment in their eyes. By comparison, humans have three with maximum sensitivities in the blue (442 nm), green (543 nm) and yellow (570 nm). It is the differential responses of these receptor cells that enable color vision.
It has been known for a long time that a light attracts fish, shrimp and insects at night. But what is the best color for a light attractor? Based on the biology of visual receptors discussed above, the light should be blue or green — the space colors of fish and members of their food chain. However, while blue or green light is desirable it is not essential. Even if the eyes of fish or members of its food chain have color receptors most sensitive to the blue or green, these same receptors have a broad but decreased sensitivity to other colors. So, if a fishing light source is intense enough, other light colors will also attract. For example, a sodium vapor light with its characteristic yellow color will attract fish — if intense enough. A fishing light attractor can also be white light because a portion of its total energy is in the blue to green region.
The perfect fishing light would have the following properties: 1) high intensity, 2) emit its light in a color similar to the fishes space (blue or green), 3) be powered by a portable electrical supply and 4) be submersible. The last attribute is desirable because significant amounts of light energy from land- or boat-mounted lights are lost by reflection off the surface of the water. No commercial light satisfies all four of these criteria. For example, many high intensity lights such as tungsten-halogen (incandescent), medium pressure mercury or metal-halide discharge lights are so power hungry that they can only be operated for very short periods of time on a battery, thus compromising convenient portability. While LEDs and fluorescent lights draw much less electrical energy, most are not very bright. Further, many of the above lights cannot be submerged in water without risk of electrical shock or damage to the light system
Types
A permanently submerged lamp used as a fish attractant.
Fishing lights fall into two different groups: those that are portable and those that are permanently mounted. Generally, portable lights are powered by batteries and this sets practical limits to the kind of light that can be used. Most portable light sources are relatively low in light intensity and have short operating times. Lights drawing more than a few tens of watts are not practical. The old classic, a 12 volt automobile incandescent headlight mounted on a Styrofoam float ring, is probably the least expensive and lasts for a few hours before the battery is discharged. Battery-operated fluorescent lamps are three times more efficient in converting electricity to light. Therefore, comparing lamps of similar brightness, they can be operated about three times longer before the battery is discharged. Also, the operating lifetime of fluorescent lights are about ten times longer than incandescent lights. Commercial portable fishing lights based on fluorescent lamps vary widely in intensity. The best use 25-40 watt lamps that emit about 1000–3000 lumens per tube. Costing $160–$200, they are available through the internet, sport stores and catalogs. Lights made up of LED lights are an up-and-comer but to date are 10 to 100 times less bright than a fishing light using a standard 25-40 watt fluorescent lamp. LEDs are extremely efficient in converting electrical energy to light. As the cost of LEDs decrease and their brightness increases, expect to see functional fishing lights consisting of large arrays of LEDs.
Permanent lights are typically powered with 115 volt house current. Placed on poles at the end of a dock or pier, the least expensive lights for outdoor use are security or flood lights using a mercury vapor, high pressure sodium vapor, metal-halide discharge or fluorescent bulb. They cost $25 to $100. While lower cost 115 V AC outdoor flood lights using standard tungsten (incandescent) or tungsten-halogen (quartz) bulbs can also be effective fish attractors, they are energy inefficient. It takes about five 100 watt tungsten lamps to deliver the light equivalent of one security lamp. Security lights are readily available from most hardware or farm supply stores. The fixture includes a photocell controller for automatic dusk-to-dawn operation and comes complete with an appropriate bulb. These lights are very bright (6-8 thousand lumens), efficient in converting electricity to light (operated daily for 8 hours, electrical supply costs $40–$100 per year), have long bulb lifetimes (24,000 hours) and stand up well to outside weather conditions. When used as a fishing light, light output can be redirected toward the water by installing a 5” X 10” piece of aluminum flashing or heavy foil bent into a half circle and placed next to the lamp‘s circular acrylic lens.
Stadium spot lights are energy efficient and their superior brightness illuminates a large area of water. Rated at 250, 400, 1000 and 1500 watts, the high intensity discharge lamp, parabola-shaped reflector and light ballast are each sold separately. A complete light fixture and lamp costs about $400–$500. The cost of lamps with different wattage ratings are similar, so most people chose higher wattage lamps. The bulbs in these lamps can emit white, blue-green, green or yellow light. For most fishing waters the lamp color of choice is green. They are available through specialty light stores. It takes two people to install these big lamps and the installation may also include a switch, timer, heavy gauge wiring and circuit breaker, thus adding to the cost.
As mentioned earlier, a significant fraction of the light shining on the surface of the water is lost by reflection and, thus, will not be available to attract fish and members of their food chain. Security lights can be modified to operate submerged in water. Positioning the bulb underwater delivers approximately twice as much light to attract fish. However, the modification must be done professionally as the high voltages that power these lamps can be lethal. Commercially made, submersible fishing lights are available on the internet. The power ballast and lamp housing is mounted on a pole in a dry location. The lamp, potted in a waterproof housing, is connected to the ballast via a waterproof cable. Floating like a fishing line bob, the lamp is positioned underwater by weights on its submerged power supply cord. The bulb is fragile so some manufacturers offer protective covers and hard lenses. However, one unique feature of the submerged, unprotected bulb is that its outer glass envelope gets hot enough to prevent establishment of marine growth. When the bulb has a protective cover or is not operated daily occasional cleaning is required.
A permanently fixed fishing light attractor is most effective if it is operated every night. It takes to a week or two for larger fish to discover the increasing concentration of bait fish attracted to the light. Once discovered, the fish return regularly — often arriving at predictable times of the evening.
"Sulfuric fire fishing" is a traditional technique practiced in Taiwan where acetylene is burned to attract fish.
