The Carp Part 3: The clever fish?

The video and text below accompanies the series “The Carp” currently running in CARPology magazine and in particular Part 3 of the series published in September's issue.

Watching carp in their own environment is always fascinating and there are various underwater videos that carp anglers can look at to see how their quarry reacts to baits and baited areas. Not long ago Radek Filip’s video and accompanying thoughts on the carp he has watched was put up on CARPology.net (click here to read more) and of course there are all Rob Hughes’s “Below the Surface” series as well as Korda’s films of the carp’s underwater world. What makes this video different is that it is part of a formal scientific study that initially shows the response of naive carp to corn and pellet freebies and to a baited hook, and then goes on to show how carp behave after they have had some experience of being caught. As such it doesn’t have high production values, it isn’t filmed in HD (or even in colour), doesn’t have catchy music or commentary. It is just a way for the scientists to show an example of the carp’s behaviour during the experiment.

The experiment itself was designed to look at various aspects of the way carp learn and respond to threatening situations. The researchers tested the carp in both ponds and large tanks in the laboratory (the large tanks being shown in this video) and used a mix of commons and mirrors. The researchers fished for them with a basic hair and bolt rig with corn as the bait and a mix of corn and carp pellets as freebies introduced every hour.

The Video

“Feeding of angling naive carp.”
00:00 - 00:016. The first thing you see are the carp swimming into view and then shooting up towards the surface. They are intercepting the corn and pellets that have just been introduced. So eager and confident are they to get to the food that most of it doesn’t even reach the floor of the tank though a few fish do drop down to mop up anything the shoal might have missed.

“First day of fishing.”
00:17 - 00:34. The rig is dropped into the circle and tweaked to adjust its position. Almost immediately a fish comes over to investigate and even before the free offerings are thrown in it picks up the bait and hooks itself. Note, as the title on the video states these are still naive carp, they’ve seen bait but never seen the rig before. You can see that the fish doesn’t hesitate and inhales the bait so confidently that the hook is well in its mouth.

“After 5 days of fishing.”
00:35 - end. Catch rates crashed after only two days of fishing and by the end of the seven-day experiment about 70% of the carp have been caught once but only 20% twice. As you can see, and unlike the naive carp who respond immediately to the hook bait, these fish are much more circumspect. They don’t come and investigate the hook bait until the free corn and pellet offerings are introduced and they are generally wary of the baited area itself. Unlike when they were naďve only one fish intercepts the free corn as it sinks down the water column and that fish spooks off the area as soon as the remaining bait reaches the bottom. One fish (at 00:50-00:54) shows very well how their attitude has changed. It inspects the free kernels and the hook bait very closely before once again spooking off the baited area. This is repeated a number of times by other individuals. The other obvious point to note is that in the five days of fishing the carp have learnt to pick up the bait in a way that helps them get rid of the hook: the researchers are ‘getting done’ by the carp and this happened more and more often as the experiment progressed. You can see that three fish in this edited video successfully get rid of the rig before one makes a mistake.

A couple of general points are worth noting. Carp, like us, are lateralised. That is they show left-sided preferences for some behaviours and right-sided for others, a trait that is essentially the same as our right- or left-handedness. Fish tend to use their right eye to view suspicious or unfamiliar objects and as you can see, the carp closely inspect the bait with that eye as they approach. In addition, nearly all the fish swim around the bait and baited area in a clockwise direction, which ensures they keep the area in view of their right eye. To these fish the whole area is suspicious, not just the rigs and bait. This observation may not help your fishing - but it’s cool to see nonetheless.

The second point is much more speculative. Even after these fish have gained some experience they still seem to have a problem distinguishing between the hook bait and the free offerings. They’re warier generally of course but seem equally wary about both the freebies and hook bait. One thing they do seem to do is eat and pay attention to the corn kernels that move. The fish that is eventually hooked picks up the bait that has just been rejected by another fish. It may be a good example of why critically balanced baits work. Carp needs cues to tell which is the bait with the hook and which is not. A bottom bait or a putty anchored pop-up that doesn’t waft around in the current created by the wash of feeding fish may not provide the cues experienced fish are looking for. A biologist would certainly want more data to see if this is true, but it’s fun to look at the video and speculate. It’s what fishermen do so well.

Naturally the video depicts a very simple set-up. To get at the root of some behaviours researchers have to strip away a lot of detail that may get in the way of finding the answer to the question they have posed. The speed of learning and the efficiency with which they get rid of the rig may take a little longer and need regular reinforcing (as on a heavily pressured fishery) but the core of the behaviour will remain unchanged. Why carp make the decisions they do, why they continue to test baits, why some seem easier to catch than others are subjects addressed in the next few articles in “The Carp” series continuing in CARPology magazine over the next few months.

(Video and research source: Klefoth et al. (2013) Fisheries. Manag. Ecol. 20:174-186 & Klefoth et al. (2012) Behav. Ecol. Sociobiol. 66: 547-559.)