Tackle and Tactics
"You must be codding!"
Every angler KNOWS that you should use a big SMELLY bait for cod when the water is dirty - or do they? You have only to read the magazines to find this message repeated ad nauseam year after year. Nevertheless, cod have a whole battery of senses that they use to find their prey. Vision is very important as are touch, vibration detection, 'smell' and taste, so, if you can, it might be a good idea to use more than one type of attraction when you fish for them. Earlier studies have shown that cod can detect food using their sense of smell from a distance of almost 700 metres and that in complete darkness (lights switched off), the cod struggle to catch free swimming shrimps.
Recently a team of Norwegian scientists began to look into how cod find their food in dirty water. In fact they designed a tank in which they could change the turbidity (=colour) by adding clay suspensions. The cod were presented with live shrimps (mysids) swimming inside tubes and the scientists filmed the reactions of the fish using an infrared sensitive video camera. To test whether the fish were using more vision or more 'smell' to find the shrimps three different tubes were fitted - clear ones (vision no scent), clear ones with holes in (vision and scent) and opaque ones with holes (scent no vision).
In the tube experiments the cod used both senses to detect the shrimps. Dirty water made little difference to whether the cod could find and attack the shrimps. The outcome of the tank studies is that the sense of smell alone allows the fish to catch still or slow moving prey but they are less effective at catching fast swimming shrimps if they can't see them. In this case vision was important even in the dirtiest water. The cod were, nevertheless, able to use their sense of smell/taste to locate prey that they couldn't see because of dirty water.
The top and bottom of it would seem to be that cod (and presumably many other fish) are more likely to find a big, smelly, slow moving bait if the water is dirty but the chances of them taking a relatively fast moving lure are reduced in turbid conditions. Well, it seems that the oft repeated, common sense, knowledge was right after all but (from my point of view) it's nice to have it proved.
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 - firstname.lastname@example.org
You must be codding!
Cod test tank set up.