I'm looking for vertical distribution or tidal height of several intertidal species, specifically from the Pacific Northwest.

I considered looking for published research for each species however, my search likely would not be comprehensive and perhaps be biased in site-specific differences.

Is there some kind of open database where I can find this information?

I've found that EOL draws some data from the Ocean Biogeographic Information System, but when I go to the site directly, I can't find the tidal height data. I've also looked through suggestions in response to this question but none are applicable.

Any help with these databases or suggestions on other relevant databases would answer my question.

  • 1
    $\begingroup$ This sounds both difficult and fascinating. I hope you can find these data! $\endgroup$
    – Kara
    Apr 11, 2017 at 22:06

1 Answer 1


I like your question a lot! I think what you're trying to achieve is the best way of solving your problem. Unfortunately, although I do have a few links for you that might get you a little bit further, a perfect solution is, I fear, not available. Tides are extremely complicated and depend on many factors. Some of these are large scale effects such as the relative positions of earth, sun and moon, but others are more local, such as ocean currents or the shape of the coast. Especially the latter can make a surprisingly large difference on a relative small spatial scale. Luckily, it is possible to come a long way and have very decent approximations.

The best option, as far as I'm aware, is to use XTide, a software program that can calculate tides at thousands of locations worldwide, making use of actual measurements as well as mathematical models. This will give you by far the largest amount of information, and the most detailed information. better still, it's open source software and completely free. The drawback is that it is complicated to use. Also, if you are a windows user, it is even more tricky as this is an X-windows program, developed for UNIX and UNIX-like operating systems (it should run fine on linux and macos). It is definitely possible to run it on windows, but I wouldn't recommend it for the faint of heart.

My second option would normally be to use rtide, an add-on package for the statistical program R, though in your specific case it's probably not good enough. The rtide package is fairly easy to use if you're familiar with R, and runs equally easily on all operating systems supported by R. The drawback is that it doesn't give as much detail as XTide, and it is based on data from a mere 637 stations, all of which are in the USA, so it's only of limited use for the Pacific Northwest. In addition, it takes more work to calculate certain variables such as the tidal range than to do the same calculations in XTide

A third option would be to use a website like https://www.tide-forecast.com/ where you can click your way to the relevant data. The number of stations they cover is even smaller than those offered by rtide, but they do cover the entire world. If you do not want to go the XTide way, then combining rtide with https://www.tide-forecast.com/ would probably be the best way to go: the former gives you a large number of stations in the Pacific US, while the latter will add some stations in the rest of the Pacific Northwest.

I hope this helps!

  • $\begingroup$ Hi Yuri, I appreciate your thorough answer however I'm looking for the vertical distribution (aka tidal height) of species. Effectively their vertical range along the shore. I'm not so concerned with the height of tides in a region but rather where animals live with respect to chart datum. $\endgroup$
    – hamilthj
    Apr 19, 2017 at 15:01
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    $\begingroup$ Oh, sorry. From your question I had understood that you had found the animal data in EOL and only needed the tidal height data that were missing there. $\endgroup$ May 9, 2017 at 11:51

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