Seasons in the Sea - A month-by-month guide to Central California sea life
Pigeon Point Lighthouse


First, I would like to say that this web site is very much a work-in-progress. As of spring 2013, I have written detailed monthly text for the months of January through May, but only have bullet points listed for the rest of the months. Similarly, I have not yet completed descriptive sections for all the various habitats and organisms. It all takes time...

The information in this web site has been gleaned from books, scientific papers, discussions with researchers and ocean experts, as well as my personal field observations. In all cases, I am solely responsible for it's contents. I will be happy to update this site as new information becomes available. Please forward any comments and corrections to

This web site is built around generalizations. However, the real world is full of exceptions. It is quite likely that, if you spend enough time around the ocean, you will see things that are different from what is described in this web site. Here are a few reasons why:

Interannual variability

This web site describes seasonal events and changes that might occur during a "typical" year on the Central California Coast. But in the real ocean, there is no such thing as a typical year. Every year is different. In fact, sometimes the variations from one year to the next are greater than the variations within a single year.

Despite this variation, many marine organisms rely on certain seasonal events for survival. Over the long run, such events must occur with reasonable consistency or these animals would not have survived. These are the types of events that I focus on in this web site.

Short-term variability

As anyone who has spent any time around the ocean knows, physical conditions can change rapidly, over days, hours, or even minutes. Marine life adapts to these changes as best it can.

Sometimes you can generalize that not one, but two possible conditions are "typical" for a given time of year. For example, you can say that clear, windy days are typical of May on the Central Coast. But so are gray, foggy, calm days.

Geographic variability

Whether it be diatoms in the ocean or mussels in the tidepools, living things tend to clump together, forming patches. Patchiness is the norm, at all scales, in the ocean.

For example, microscopic algae such as diatoms are often concentrated in distinct layers, which may be only a few meters thick. They also form large patches in area or are concentrated in gyres or at the boundaries between different water masses. Patchiness within patchiness creates a fractal pattern, and leads to greater diversity in life forms.

At a larger scale, there are huge variations along different parts of the Central California coast with respect to waves, winds, currents, and the physical properties of the sea water. These affect the types of plants and animals that live in different areas at different times of year. Even within a single rocky cove, micro-habitats are crucial to the survival of many smaller plants and animals, whether they are trying to survive the battering of storm waves or escape predation by larger animals. Finding just the right conditions is everything.

Our profound lack of knowledge

Even though the Central Coast is one of the most heavily studied coastal regions in the world, we don't know all that much about what's going on out there. We are still discovering or naming new species, particularly in the deeper waters. Marine biologists are still trying to figure out the complete life cycles of many animals and algae, particularly the time they spend as drifting larvae or spores.

I will try to keep this web site up to date as new discoveries are made. However, I cannot guarantee that all of the information is current. This is especially true for species names, which are being revised frequently these days in response new DNA analyses.

Climate change and long-term cycles

What has been "typical" for the last 30 years (when most of the trends in this web site were documented) may or may not be typical three decades from now. This is in part due to long-term cycles in the climate. Some of these, such as El Ninos, last just a few years. Others last decades or generations.

Combined with these long-term cycles is a long-term warming trend in both air and water caused the increasing concentration of carbon dioxide in the Earth's atmosphere. Such warming can have profound changes in the seasonality of many activities, including migration, reproduction, etc.

It is well documented that flowers are blooming earlier in spring and birds are staying later in fall in many temperate and especially sub-polar regions, because of these warming trends. It is much more difficult to document such changes in the ocean. But it is very likely that the seasonal activities of many ocean organisms and processes are also shifting in response to global warming.

Already biologists have found evidence that populations of intertidal animals in Central California are changing, with greater abundance of warm water species and fewer cold-water animals. Similar, fisheries biologists have also shown that some open-ocean fish are spawning two to six weeks earlier in spring than they did in the 1950s.

Final disclaimer: This is not an authoritative source for decision-making

For all the reasons stated above, this web site is full of generalizations. It was also created by a single, completely fallible human being. Thus, the contents of this web site should not be used as a basis for decision-making, permitting, or other activities that have a significant impact on the coastal environment. Similarly, the information should not be used as a sole basis for planning activities in which the participant may be endangered by the environmental conditions encountered. The author is not responsible for the any damage or injury relating to use of the material in this web site.

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