When we think of carp feeding, how often do we think about what the carp is actually doing? Sure we test our rigs by pulling them over our palms to see if they turn over the right way, and this is useful – but how useful? There have been some in-depth studies on just how carp handle the food they have in their mouths, but very little seems to have made it into the hands of carp fishermen (or if it has they are not saying!). This article is a summary of the very informative and extremely long (43 pages) carp food handling study by F. A. Sibbing, J. W. M. Osse and A. Terlouw and will hopefully help with construction of rigs that might be a little better at not getting ejected.
Before we get into the mechanics of feeding lets take a quick look at how carp find their food (this is not part of the study). Carp have an excellent ability to detect food in their environment using taste, sight, and vibration/movement (via the lateral line). Taste (taste and smell are pretty much the same thing for carp) is likely the most often used sense as it is not affected by water clarity and requires no disturbance to create vibrations. Taste buds are not just found in the mouth of carp, but also around the outside of their mouth and over much of their body, including their fins. So when you watch a video of carp feeding underwater and they brush over the bait they are “tasting” it – without any chance of being hooked! Once food is located the other two senses come into play. If the water is clear and there is adequate light, sight can play a big roll. There seems to be two main methods here. If there is a large bed of corn the visual cue can get the fish into position and then it can simply start vacuuming it up. However, if there is a lot of scent in the water and few obvious targets, sight may guide the fish to individual items. This is where a hi-vis hook bait could really work well as it will give the fish something to key in on. Vibration is caused by movement in the water, and a crayfish moving across the bottom would be a good example of where the lateral line would help to find some food.
Once food has been located and the carp has decided to capture it, the following sequence of events unfolds. First it will open its buccal cavity (mouth) and create negative pressure that will pull the food into its mouth. There are two types of suction that can be used: one for food on the bottom that is concentrated on a single point, and one for suspended items (think plankton) that sucks in more water but with less force. The anterior pharynx is closed at this point to allow the various components of what it has just sucked in to be separated, with the heavy items like sand falling through the gill slits.
If the intended item is larger, like a clam or boilie, it is then held by the palatal organ and “washed”, after which it is crushed and washed further to remove any bits of debris. However, the carp may decide that the boilie is not really that good after all and try and get rid of it!
Here is the part we all care about: if the carp decides to eject the bait. The carp’s mouth is opened and the gills are rapidly closed to create a jet of water to wash out the non-food item (your bait). The part that I really think is overlooked is the last bit. Once the carp’s mouth is open and the water is being pushed out, the rear of the buccal cavity is brought up. This in effect causes the floor of the mouth to “fall away”, making it harder for hooks to catch.
So what do you do to try and improve your rig? You hear a lot about making the point of your hook heavy, and this makes a lot of sense looking at how the carp eject the bait. The hook and/or the point ideally needs to be heavier than the bait as it has to fall faster than the fish thinks it is going to, and therefore catch the lower lip. What about the hook “flip” test? For what I have seen in this study as well as watching lots of underwater footage, it seems that the ability of the hook to turn over is useful but likely not the end of the story when it comes to hooking fish every time you bait is “sampled”. Simply having the hook in the right position does nothing if it never comes in contact with the carp.
KD, blow back, and D rigs are all make the point of the hook heavy and should be better at hooking, but this is open for debate. I hope you find this information useful and are able to fine tune your rigs to get a few more fish on the bank.