Understanding Tide Tables and Charts

Understanding tide tables and charts is quite easy once you understand a few key topics. The chart below will help you see how the currents move and just what to expect during the changes. The Oregon coast has its' share of rip currents and the unexpected "sneaker waves" so the rule of thumb "never turn your back to the ocean" can save many lives each year.

     An Aid in Understanding Tides Tables

Using the example above there are a few key points which I hope to explain in more detail. This should aid you in both your dungeness crabbing and clamming adventures as well as how the ships move through the harbors and what you might expect and certain times. The chart I've made above is merely a learning tool and not an exact replica of a days tidal movements. The above chart is most normally found as a table in a tide book and would appear as follows:

Saturday 2004-10-02
Sunrise 7:16 AM PDT, Sunset 6:55 PM PDT
Moonset 11:50 AM PDT, Moonrise 8:58 PM PDT
High Tide: 2.25 P.M. PDT 10.00
Low Tide: 9.08 P.M PDT -0.07
High Tide: 3.40 A.M. PDT 8.00
Low Tide: 9.00 A.M. PDT 3.00

A very common misconception is the thought that since there are four tides daily they must be on a six hour schedule. This, however, is not true if you look closely at the times. The tides are *not* on an exact 6 hour schedule as many might think . The period between tide cycles is very "roughly" about 13 hour from high to high or low to low. Factors such as moon phase, time of year, and your position on the globe are just a few on nature's way which determine how the tide's flow. My goal here is not to explain these external components but to simply help you understand how to read a store bought tide book and my weekly tide tables.

What does it All Mean


The first thing I'd like you to notice is the areas above and below the red lines. These periods are called slack tides and are perhaps the most important time of the tide periods whether it be high or low. A "slack tide" is the very short period (from 1 to 3 hours "generally") when the ocean is close to a balance in tidal movement. These are the times when crabbing on the "high slack" side will be the best and when clamming on the "low slack" side will be at it's peak. The main reason crabbing is at it's peak during these times is the fact that the currents are not moving nearly as strongly as they are further down the tide time line. The crabs can move easily without fighting the tide and therefore are much more active. Once the tides really start to move fast the crabs will often dig themselves under the sea bottom. This is when they'll tend not to feed nearly as much as they will the tide is rather calm. You may also do very well crabbing on the low slack tide provided the water you are fishing is deep enough.

I hope this better explains some of your questions about the tides. I strongly believe that if you use the information which I've provided on this site that you'll learn to know the best times for activities such as crabbing, clamming, ship watching, and tide pooling.