Domoic acid stories seem to crop up each year and generally when fish are affected the California Fish and Wildlife will issue warning letters. Given this is from an environmental group I would not panic just yet although we all need to pay attention in case warnings from the Fish and Wildlife do occur. The one thing I found strange was the reference to upwelling which is a natural event that occurs each year and helps sustain ocean life.
From Pier Fishing In California, 2nd Edition — "water temperatures are not the only answer to the question of why fishing is better during certain months. The conditions resulting from the water currents, and differences in water temperature, are modified by an additional process called upwelling. Upwelling, as seen in California, is fairly unique, being limited to four temperate areas of the world, the so-called eastern boundary regions (California, the west coast of South Africa, the Canary Island region, and the Peru-Chile coast). This condition is caused by California’s seasonal wind patterns and explains why ocean waters are sometimes rich with food while at other times they may be nearly barren. Generally starting about March, northwesterly winds and the earth’s rotation cause surface waters to be driven away from the shore and to be replaced by cold, rich water pulled up from the deep continental shelf. This upwelling is common along most of California’s coast and is especially prevalent north of Point Conception in areas where there are headlands or where there is a sheer coast.
The water rising from the depths brings with it decayed organic material that has sunk to the ocean’s floor (and which has not been utilized by plants since few plants exist in the dark deep-water areas). This nutrient-rich water (which contains phosphates, nitrates, and silicates as well as other nutrients) reaches the well-lighted surface areas and stimulates a tremendous growth of tiny plants, algae called phytoplankton. As summer nears, this plant growth blooms and waters can be darkened by billions and billions of emerging plants. Winter storms are now over, sunlight lasts longer, and surface waters are warmed. These changes also create ideal conditions and food for the second important planktonic organisms, small animal organisms called zooplankton (tiny jellyfish, shrimp-like krill, copepods, and larvae of many species including fish).
This synergistic explosion of vegetable and animal organisms creates a rich and nurturing bouillabaisse of food that gives sustenance to small fish such as anchovies, herring and sardines (as well as large organisms like whales). These small fish attract the larger fish. Along with the growth of the smaller plants (phytoplankton), larger algae in the form of kelp also grow during these nutrient rich-sunlight rich months. This kelp, which can be dense around some piers by late summer, provides additional food and shelter for fish.
An additional factor, most evident in southern California, is that this upwelled water is not only cold but also low in oxygen and high in salts. As a result, there is a change in fish distribution; fish are more concentrated in inshore areas (top to bottom) and upper level offshore areas. A number of species that spend part of the year in deeper offshore waters move into inshore waters—like that around piers. Offshore, there are concentrations of bait and pelagic species.
Generally around September California's northwesterly winds begin to subside, cold upwelled water begins to sink, and phytoplankton and zooplankton populations begin to decrease. At the same time, surface water temperatures now reach their highest levels and southern California anglers may see their top fishing for the warm-water pelagic species. This condition, called the oceanic period, lasts till about the end of October when water temperatures begin to cool.
In winter, southwesterly winds dominate along California's coast. One result is a northward flowing surface current which begins north of Point Conception and flows along the coast inshore of the California Current. This current is called the Davidson Current and represents the surface manifestation of the California Countercurrent (which normally flows under the California Current). This means that in winter there can actually be more warm water flowing north than in the summer. However, there is much less sunlight and little upwelling during the late fall to spring months. Correspondingly there is less phytoplankton and zooplankton, the tiny organisms that are so important for the growth of fish populations.
For most of the California coast, fishing will be best when there is a good population of plankton (or food) in the water and when fish are attracted and concentrated by this food. As shown, the plankton populations (both phytoplankton and zooplankton) begin to improve as upwelling begins in March, peak around September, and show a serious decline by November. Piers generally see their best fishing in the late summer to fall months and see, especially at southern California piers, a continued success till October or even November for the warm-water loving pelagic species. Schools of bonito, barracuda, and mackerel follow the schools of plankton-seeking anchovies, sardines, and other small fish.
