Scent Composition And Dispersal In Plastics

From the early days of pork rind soaked in brine, bass fisherman have been at the forefront of using scented artificials, probably as long if not longer than anglers using scented baits to lure bottom feeding fish such as carp. Scents are one of the most important features of modern soft plastics and their development has proceeded in leaps and bounds since we first used to buy them during our school days. In chemical structure bass scents are dominated by oils that are similar in structure to the plastics from which the lures are made. This is very convenient as oils are also very good long term carriers of scent. A newer generation of scents is also water based which increases its scent dispersal efficacy. Plastic worms, lizards, frogs, grubs, flukes and others are made from Polyvinyl Chloride mixed with and oil-based resin which is what makes them so soft. Softer plastics have more resin in them and vice versa. This is what gives cheaper plastics that distinctive plastic smell, similar to water piping. As I mentioned earlier, it is this oil-based resin which the scent is dissolved into and which slowly escapes as you’re working the lure through the water. Small tears and cracks in the bait’s moulded outer surface also allows more scent to escape. Top brands are undoubtedly at the leading edge of developing more advanced and realistic scents in plastics with their lures universally known to be brilliant fish attractants. Companies producing soft plastics invest huge amounts of money and technology into developing unique scents to infuse their lures with, although they obviously keep the structure and chemical as trade secrets. The plethora of scents that we have in plastics today is by no means purely based on imitating natural scents, but the foundation of many bass scents is simply a salty tasting oil. The exact scent that bass plastics imitate is a mixture of scents that smell “fishy” to people or like something a fish would eat. For bass this can be anything from garlic, cheese, liquorice, brine, to more advanced imitations of real scents. More realistic and natural scents are typically an oily, fatty or organic smell that you would associate with the lymphatic fluid, haemolymph or muscle tissue of aquatic prey animals. Such compounds can be isolated by chemical techniques such as high pressure liquid chromatography (HPLC) which will give you an indication of the molecules responsible for your favourite scent. For instance, the strong fish mucous smell of carp is caused by the molecule geosin. Nearly all modern plastics are scented to increase their attractiveness. This is a selection of flukes, frogs and lizards showing how the oil drifts off and disperses scent to lure bass. To gain some insight into this you can drop one of your favourite plastics into a clean glass filled with clear water and you will see a very faint oil slick on the surface, it is however very faint. When you take the plastic out of the container, the water is repelled and runs off. However, if you drop that same lure into a glass of vegetable or plant oil, a different story emerges, namely the oil completely coats the lure in a thick layer that keeps sticking to the lure when you remove it. The oils that are used on bass lures are thin oils, meaning they have a low viscosity which causes them to easily shear off the lure, forming trails of minute oil droplets that collect and form a trace slick around the lure and along its swimming path. Thin oils can also be absorbed into the upper surface of the plastic making the scent last that much longer. Bass oils are not only coated onto the surface of the lure but they are adhered in a form of salt. These scented crystals are very commonly seen in packets of plastics. This is a common trick o f chemistry to increase the solubility of oils. Oils are hydrophobic and repel water, but when adhered to a salt the oils break up as the salt dissolves forming an emulsion which is effectively the scent cloud around the lure. Scent dispersal in bass plastics is short distance. This is not because the scent itself only travels a short distance, but because bass, unlike carp, eel or barbel don’t move long distances and congregate in response to perceiving a enticing scent. I’m speaking specifically of largemouth bass here. They will start to scout around their immediate surrounds and become more vigilant around their structure and cover, but scent becomes important when that lure is close to them and they almost “expect” to smell it. Biologists refer to this as a form of appetitive behaviour, where the animal expects to see a prey animal when picking up a specific scent. While bass scents have become an integral part of plastics, I still believe that there is a lot about the finer details of bass scents that we don’t understand and don’t exploit as effectively as we could. One of these is certainly whether there is a lot of seasonal variation in the response of bass to different scents. It makes sense that bass will be more sensitive to some scents during spring and others during full summer and potentially winter. The exact types of scents that bass will be searching for is directly related to the types of food that are available at different times of the year. For instance from spring larger prey such as fish fry, frogs and crabs become increasingly active and are available food sources. Thus lures with strong fish scents are likely going to be effective during these times. Bass in South Africa are not exposed to very well timed emergence of prey as is the case in their home ranges with species such as Salamanders, Frogs, Shad, Bluegill etc., thus our fish are used to a mixed bag of prey available throughout the warmer months.