It's a safe bet fisherman have been keeping track of their catches since long before the advent of the fishing hook. No doubt there are cave drawings somewhere of Og and his friend Bog nabbing fish in a creek with only the benefit of their opposable thumbs. Maybe there's a cloud in the image, and a quarter moon, describing when the catch was made.

Eons later, we've evolved a complex information network to tell us where and when the fish will bite, and anglers seem less eager to make their own notes. Click on the Internet, watch television, pick up a magazine and-Presto!-directions to the hot bite.

Still, anyone who keeps his own log will tell you it's as helpful as ever. It's also satisfying on a personal level.

Just what exactly is a fishing log? Well, not many of us chisel the information on the walls of our living rooms like Og and Bog. Some anglers use a simple spiral bound notebook for each year, while others buy one of the handful of commercial logbooks on the market. The latter usually feature spaces for relevant data like tides, moon phases, weather conditions and fishing techniques.

For my own log, I use a computer to keep records and observations on a word processing file (backed up on disk, of course).

Here's a sample entry from a recent trip:

Sept. 22: Tarpon Bay with Tiff. Five days after new moon. Falling tide in morning: high 2.5' 5:11 a.m., low .3' 12:57 p.m., back to a level 1.6 at 8 p.m., to 1.5 at 11:24 p.m. Light west wind. Found tailing redfish along sand/grass bar south of canoe launch; seemed most active between 9:30 and 11:30 a.m. Caught one and lost two on gold spoon; also caught one on yellow weedless Seaducer fly. Low tide unproductive-fish moved off into deeper water. Lots of mullet.

The trip was to Tarpon Bay, a little cove on Captiva Island. I included tidal information from the appropriate NOAA tide station, in this case St. Petersburg (the back side of Captiva being about an hour behind that figure according to my Fishing Planner), and I noted a two-hour window when the reds were digging hard for food. It would be a stretch to conclude the fish will be in the same place at the same tide stage next year, but the entry does give me something to steer by: strong falling tides in autumn.

There are many details you might put in your log. Location is a no-brainer, but don't just write "Sebastian Inlet." Tell at what side of the inlet you were fishing, or in what depth. If you're fishing a wreck or reef, note the latitude and longitude (you might keep a separate log for those coordinates, as well).

Pay attention to weather trends, even if you don't write them in scientific meteorologese (water seemed unusually fresh from recent rains). Barometric pressure, wind speed and direction, air and water temperature-in the long run you'll benefit from as much data as you can squeeze into an entry. Remember that conditions on your fishing day are important, but so are major events like droughts, tropical storms and cold fronts. Over the years, a log helpsyou tune in to patterns and how fish react to them.

In my home waters off Miami, I do a lot of livebait fishing along the edge of the Gulf Stream. My basic strategy doesn't change a lot from month to month, as it's pretty effective on whatever happens to be passing through, from sailfish to kingfish to dolphin. What I've found really helpful in this area, however, is to jot down the whereabouts of bait. If I have a general idea of where pilchard schools should be at a given time of year, for instance, my day is that much simpler. Were they inside Government Cut? On the grassbeds near Broad Causeway? The log can result in significant savings, as I don't spend nearly as much time and fuel running in search of bait.

A lure fisherman would surely want to recall at what time of day the bite switched from topwater to jigs, for instance, or whether a fast or slow retrieve was best. Tackle and technique information can be helpful later on. The bass guys have this down to a science, but saltwater anglers can use the approach as well.

You may want to add a separate section on boat maintenance. Boat service intervals are particularly valuable. When was the last time you changed your lower unit gear lube? If you run a four-stroke, when did you change the oil? How long has it been since you waxed your hull?

And of course logs can be entertaining. It's fun to look back and see who you fished with and what you caught. You can also add non-fishing details to help you grow as an all-around outdoorsman. What day was it that you saw the flock of ducks heading south for winter? Have you ever actually seen a manatee in that idle zone?

Lastly, don't neglect to enter the bad days in your fishing log. Though none of us likes to admit it, much of our lifetime angling learning takes place through process of elimination. So put your pen to paper or fingers to the keyboard: Discovering where the fish aren't likely to be is just one step toward figuring out where they are.