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"Catching cod - a bit of science.".

It's the time of year when many sea anglers start thinking seriously about fishing for cod and whiting. Of course the magazine editors are well aware of this and usually you will find pictures of the grinning captors of twenty pound cod on the covers of the mags. However, popular as these fish are, it is rare to find any solid information about their behaviour which will help you to catch more fish. I suppose that in these days, with the parlous state of cod stocks it should be catch and release. Anyway, here's some stuff I came across a few years ago that really does spell out how a change of tactics could improve results.

Every successful angler must know quite a lot about fish behaviour. This is just as true for the conger catcher as for the dace dangler and for the mackerel man as for someone in pursuit of pike. Nevertheless it is much easier to see the value of a bit of 'know how' in fishing for a species such as the trout in fast flowing rivers than for most sea fish. Although what I have to say is mainly about cod - a few thoughts about trout make things clearer.

We know that trout are territorial. A bigger or stronger fish will chase lesser specimens away. All fish try to get the most food while spending as little energy as possible so the biggest, fittest trout will be in the best spot. It will be sitting in the shelter of a rock or weed bed where a swift current brings lots of drifting insects past its "front door". It follows that the trout angler MUST cast his or her fly (or in my case, more often, his plug, minnow or worm) into exactly the right place.

Secondly, trout fly-fishermen have invented a detailed list of the ways in which a trout will take a fly. A little fish will splash wildly at the surface in its haste to grab a meal, while an older, wilier specimen will simply sip the insect in. Fish taking hatching nymphs will make a characteristic bulge at the surface and emerging, drifting or egglaying flies will each be seized in a recognisable fashion. Any trout angler will tell you that it is essential to understand the basics of these behaviour patterns if you are to catch fish (of course this isn’t strictly true but it does help at times).

Where does this leave us with the cod? Well the facts of life are no different for Gadus morhua than for Salmo trutta, the biggest, healthiest and fittest fish will be those that hog the best spots and catch the most food. Of course we know that cod, and other species will congregate around rocky weedy outcrops and ledges but these are complicated places. There are too many factors involved in this sort of mark - cover to escape from predators, a wide variety of food items, the chance to ambush prey and so on. What about a simpler case where the fish are over a clean bottom?

Cod will often hunt for sandeels over rippled sand or gravel. Places like the Skerries or the Shambles banks and many other similar fishing grounds, around our coasts, are good examples. In these places the strong tidal currents sweep up huge mounds of coarse grit and shells. These mounds are sculpted by the flow into giant ripple marks. Scientists in Lowestoft have now described the reactions of both wild and captive cod over such ripples.

As you might expect, when water flows were slow the cod preferred to swim above the ripple crests. As the flow increased (over half-a-metre-per-second) the fish took shelter in the troughs but only when the ripples were about twice as far apart as the body length of the cod. At very fast flows the fish again emerged from the troughs to swim freely, possibly because the flow was too turbulent for them to shelter.

What does this mean to the boat angler? It is a neap tide. It’s half flood and the current is running fairly hard so you need about four ounces of lead on your 20lb braid. You are in the stern of the boat, anchored uptide of the sand bank. As you pay out the line you feel the weight hit bottom and then you sink and draw to carefully trip the tackle back over the ridges of sand - up over the crest and down the far side. You feel the lead clunk down into a trough and wallop! You're into a decent fish. It battles hard and after a few minutes a twenty-pound cod is brought to the surface. Several more fish follow, each time the bite comes just as your lead drops into a trough.

Eventually the tide slackens and the bites cease, even though you have reduced your weight to two ounces just to keep it on the move. You decide to up anchor and drift across the bank with a baited pirk - straight away the new approach pays dividends, producing another good fish within a couple of minutes. This time the take comes three or four feet above the top of the ridges - magic! A bit of scientific knowledge can be useful at times.

A recent Norwegian study on cod adds a bit more to our knowledge. Again the scientists used both wild and captive reared cod, this time to see how they fed on live fish. The prey were little two-spotted gobies. Each cod was presented with fifteen gobies and given half-an-hour to eat them.

To cut a long story short both reared and wild cod were NOT INTERESTED in stationary gobies but both reacted instantly to moving prey. The "tame" cod were, not surprisingly, less efficient at catching prey and often got involved in a chase. Wild fish on the other hand were very smart and simply lunged at the gobies using much less energy. Clearly cod that have to capture other fish in the open sea must rapidly develop an effective hunting strategy or they will quickly starve to death. This presents a real challenge to farmed cod released into the wild - adapt or die. The same problem must face any tame animal that is set free.

What does this bit of science tell anglers about cod fishing? First and foremost I would say that it is not a good idea to leave your bait stationary on the sea bed. Any movement, which you can impart, either by drifting the boat, sink and draw, cast and retrieve or even by using a long trace which allows the bait to wave about in the current, has got to improve results. Of course all these things are the basis of good angling but it is reassuring to know that the tactics which you have been doing for years have a sound basis in the facts of fish behaviour. .

If you have any comments or questions about fish, methods, tactics or 'what have you.'get in touch with me by sending an E-MAIL to - docladle@hotmail.com

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