Some behaviour is so clear that it is easy to pick up what the fish are doing, but often just trying to remember when and on what gear you caught what fish is impossible. I must admit that am not the best person in the world at keeping a diary - hell, I don't even own a watch - but I am absolutely convinced of the usefulness of the information contained in catch records.
Now, as this article is being published on the web I guess you all have access to a computer, and that many of you will also be running Microsoft software, as I do. Most anglers that I know keep a diary, but this is actually not a lot of use for actually seeing patterns in your catches. Much better are spreadsheets, which allow you to display the information you collect in a number of ways. After playing about with Excel for quite some time, I'd like to offer some tips on the way to lay this information down, and how to get the most from it.
Firstly, I record every session, be it a blank or not. Knowing when not to go fishing and what not to use is just as important to me as knowing what is right. Secondly, fish capture must go in a separate row, so that I can look at features such as time of day when fish are caught, average weight and preferred baits.
How much information you record is up to you. The table below shows a very simple spreadsheet for this Spring's tench fishing on a new lake. Now, I had already worked out the right swim, methods and baits, so this information was not included. Obviously, you can include anything you feel relevant to the waters you fish, but being lazy, I tend to keep things relatively simple.

Tench sessions Spring 2000

Date Start time Finish time Weight (decimal) Time caught
29/4/0017.5246.9518
30/4/000246.919
8/5/000127.27
10/5/001724
11/5/000197.959
13/5/001924
14/5/000249.158
14/5/000245.9511
15/5/0009
22/5/001924
23/5/00097.17
29/5/001924
30/5/000116.957
30/5/000117.158
7/6/000127.56
7/6/000127.46.5
7/6/000126.957
7/6/000126.058
19/6/000127.357
19/6/000127.58
7.203333



Analysing the information takes a bit of practice, but I have found one of the most useful features to be the 'stock' graphs option. Look at the spreadsheet and you will see that the columns after date contain information on when the session started and when it finished. If you create a graph of this information, plus the time of capture of any fish it looks a little like the graph below
As you can see, the tench were incredibly predictable in their behaviour, with virtually all the fish being caught in a three hour window around mid-morning. You will also note that as the venue is some distance from home, most of my sessions were overnighters. Unfortunately, although I knew that I was wasting my time, the distance involved made it impractical to only fish during the hot period and so I was forced to sleep at the lake.
This is only a really simple example of the kind of pictures you can get by looking at your catches on a spreadsheet. I am sure you can think of many other ways of looking at it, and if you take a look at Stu Clough's article on barbel fishing you can see how Stu has used a similar method to analyse his catches. If you keep a diary already, or if you are thinking about it, then the digital approach certainly makes working out what the fish are doing much easier, why not give it a go?