Water temperature and fish...

Ken Jones

Staff member
From Pier Fishing In California, 2nd Edition

California Currents—The Angler-Scientist

Two questions about California's saltwater fishing have always interested me: why are different fish found along different parts of the coast and why do different times of the year show such differences in fishing success—or lack of success? The answer to the first question is fairly easy, the second demands a more complex explanation.

For geography and species association the primary answer is water temperature. California’s warm-water species, fish like yellowtail, barracuda and corbina, are rarely found in the colder waters found north of Point Conception. Cold-water species like salmon are rarely found in the warmer waters south of the point (although the overlapping of northern and southern species does sometimes occur, for two quite different reasons).

As to angling success and time of the year? In California, saltwater fishing tends to start improving during the late spring and peaks in the late fall. Why? One answer is again water temperature, at least for southern California. Summer waters are warmer and see an influx of fish from Mexican waters. For pier anglers this means more pelagic species like bonito and barracuda. Another reason is that the summer water is much richer with food and where there is more food there are more fish. That sounds simple. But why is there more food (plankton) in these waters spring through fall? What are the conditions that create this situation? California's marine waters are primarily influenced by two factors—the offshore currents and the prevailing wind patterns—and these provide the answers to the puzzle.

To the north, along the northern and central California coast, water temperature is influenced by the California Current and the California Undercurrent. The California Current is a strong southward flowing current that has already passed though the cold-water areas of Alaska, Washington and Oregon. This cold-water current warms as it flows south (paralleling the north-south orientation which is common to most of California’s coast)—but it is still primarily a cold-water current. The slightly warmer undercurrent flows northward, inshore of and beneath the California Current.

• General water temperatures: Oregon Border to San Francisco
Winter: 46 to 50 degrees Fahrenheit
Summer: 52 to 58 degrees Fahrenheit​

• General water temperatures: San Francisco to Point Conception
Winter: 48 to 53 degrees Fahrenheit
Summer: 52 to 64 degrees Fahrenheit​

At Point Conception, the coastline begins an east-west orientation while the California Current continues its southward flow. As a result, the cold water is now carried out, away from the coast into deeper waters. A different, northward flowing, warmer-water current, called the Southern California Countercurrent, hugs the coast and becomes dominant, especially in the waters of the Santa Barbara Channel, the waters most commonly used by Southern California's recreational fishermen.

• General water temperatures: Point Conception to Mexican Border
Winter: 50 to 54 degrees Fahrenheit
Summer: 64 to 74 degrees Fahrenheit​

These currents are the primary influences on water temperature and explain why different species are found in different areas. In essence, the California angler is faced with water that is cool (or cold) north of Point Conception and water that is warmer south of the Point.

Pier waters in the south, being inshore (and influenced by the Southern California Countercurrent) typically have somewhat warm water reflecting the cold-north, warm-south conditions. As a result, Southern California piers rarely yield up northern species to its anglers. However, the deeper, offshore waters in southern California (especially where influenced by the California Current) will be colder and more approximate that of northern areas. This is why deeper waters in southern California will sometimes yield cold-water fish common to shallower waters north of Point Conception, fish such as lingcod.

As a general rule, California’s cold-water species are found where water temperatures do not exceed 55 to 60 degrees Fahrenheit for extended periods of time. Warm-water species do tolerate warmer temperatures and (for some reason) are better able to endure considerable periods of cold water. Thus at times warm-water species will be found in cold-water areas (such as finding garibaldi and kelp bass in Monterey Bay) while it is rare to find cold-water species in southern California (again, except for the deeper and colder-water areas.)

But, 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. This 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.

Ken Jones

Staff member
I think, in looking back, that I should have changed part of that last paragraph to read:

Piers often see their best fishing in the late summer to fall months and can see, especially at southern California piers, a continued success until October and even (some years) into November for the warm-water loving pelagic species. Schools of bonito and barracuda are sometimes most common during those late fall months. Generally though, by November, there seems to be a transition from the warm water to cold water months and fishing starts to show a drop-off in catch.
Is the amount of upwelling tracked and plotted on a yearly basis? I'm curious to see which years were high upwelling years and which ones were low. I imagine there might be an online resource for this.

Ken Jones

Staff member
I'm not sure if the upwelling is tracked every year although Scripps in San Diego seems to track almost everything these days. There certainly are changes that take place during El Niño years. Here's more from PFIC and are a few short readings on the subject that I will be including in the new edition if one is ever published—

PFIC—Water Temperature — Most years the letters to the Pier Fishing in California Message Board are fairly predictable, especially those concerning the fishing—good and bad—taking place at the piers. They're cyclical, reflecting the nature of pier fishing in our state. Winter and cold weather can bring a drop-off in success along with a general depression among the pier rats. Then summertime returns with its better weather, warmer water, and ameliorated conditions for the fish. Soon the pier rats are happily catching fish and grinning from ear to ear. Unfortunately, the wintertime letters are sometimes almost manic-depressive in nature with pier rats throwing up their hands and questioning if the fish will EVER return. It's as though incubi had cast an evil spell on the fishing—and the mood of the pier rats.
Most of this agony can be avoided. One way is to live to be as old as I am; it gives you enough years of experience to make comparisons. You soon realize some seasons are good and some are bad, just as some years are good and some are bad. You can also continue to study the ways of fish and their environment. You may not be able to change the conditions but you can at least understand what is happening.
This means, in part, understanding the water world in which fish live. Water temperature is critical! In fact, scientists say water temperature is the single most important factor affecting the behavior of fish. Water temperature largely defines the nature of California saltwater fishing, and the various sea currents that flow along California's coast help determine the water’s temperature (see the highlighted California Currents—The Angler-Scientist). [see above] Certain species are common to the warmer waters south of Point Conception while other species are indigenous to the colder waters north of the point.
However, water temperatures change. There are annual changes due to global conditions, and sometimes abnormal situations such as the El Niño (“The Christ Child”) which brings warmer water to California. During moderate/strong El Niño years (1957-58, 1965-66, 1972-73, 1976-77, 1982-83, 1987-88, 1991-92, 1997-98, 2002-03, 2015-16) central and northern California areas see warm-water fish being caught that are more normal to San Diego and Los Angeles. Los Angeles and San Diego will generally see some species that are common to Baja, California.

There are currently several hypotheses as to why El Niño events might affect coastal organisms along the Pacific Northwest. One hypothesis is that El Niño conditions, by affecting the timing and effectiveness of upwelling, result in a diminished supply of nutrients to surface waters. Fewer nutrients adversely affect phytoplankton growth, which, in turn, means that there is less food for small animals (known as zooplankton) that feed on phytoplankton. During the El Niño event of 1982 to 1983, the average spring and summer density of zooplankton off Newport, Oregon, decreased by 70 percent. This effect can reverberate up the food web, threatening the survival of juvenile salmon that eat the zooplankton.
El Niño conditions can also reduce the movement of water away from the coast. Juvenile salmon, too small to swim against the currents, rely on the offshore transport of water to whisk them away from the coast. In El Niño years, juvenile salmon may get trapped near the shore and fall prey to seabirds and other coastal predators.
In addition, changes in the direction of coastal currents and in water temperatures can directly determine the types of fish found off the Pacific Northwest. During the El Niño of 1982 to 1983, fish that normally inhabit tropical and subtropical waters migrated northwards, following warmer waters. For example, two warmer-water species, the Pacific and jack mackerel, were unusually abundant off the coasts of Oregon and Washington. These voracious predators consume the same types of food as salmon and may have diminished the supply of phytoplankton and zooplankton; in addition these fish may have snacked on juvenile salmon. —El Niño, (Oregon Sea Grant), Sandy Ridlington, Editor, 1997

PFIC—Balancing off the El Niño, warm-water conditions, is its cold-water cousin La Niña (“The Girl”) aka El Viejo (‘the Old One”) that brings unusually cold surface waters and intensified winds. Conditions can often swing between the two conditions as seen in the moderate/strong La Niña years 1955-56, 1963-64, 1966, 1970-71, 1973-74, 1975-76, 1988-89, 1998-99, 1999-00, 2007-08, 2010-11, 2011-12). Following the super-hot El Niño years of 1997-98 there occurred a La Niña in late 1998 and ‘99 that saw waters along the coast drop down to a low of 46 degrees in some areas. Talk about a contrast! The result was a much later season and a return to the cold-water conditions more common to California. No longer were the exotic species being caught to the north but the upwelling along the coast was improved as well as the survival rate of various species of fish. Even the growth of kelp increased with the return of the needed cooler waters.
Although the positive effects from El Niño conditions seem to influence pier fishing along much of the California coast, at least north to San Francisco, the negative effects from La Niña seem primarily to affect the areas north of Point Conception (in my opinion). As example, although there was a slight decrease in the catch at southern California piers in 1999, there was a dramatic decrease along much of the central coast including San Francisco Bay.

Since 1800, there have been approximately 48 El Niño events, with a mean frequency of one event every 4.1 years. Although El Nino events occur frequently, they are difficult to predict and highly variable in intensity. Some El Nino events are relatively weak whereas others may affect the entire Pacific Basin. Particularly strong El Nino events occurred during 1957-1958, 1982-1983, and the strongest El Nino on record occurred in 1997-1998.—Satie Airame Steven Gaines and Chris Caldow, Ecological Linkages: Marine and Estuarine Ecosystems of Central and Northern California, NOAA, November 2003

PFIC—There are also normal seasonal variations in water temperature, and some species enter or leave our California waters accordingly. Finally, there are daily variations depending on weather conditions. Shallow water areas tend to both warm and cool at a quicker rate. Deeper water maintains a more constant temperature. During abnormally hot weather, fish may migrate into deeper areas where the water is cooler. During a cold spell it can be just the opposite; fish may move into shallow water during the middle of the day because it is warmer. Thus, if you are fishing a pier during the middle of a hot, sunny, summer day you might want to first try the areas of the pier with deeper water. At dusk, as the water begins to cool, inshore fish will move back to their preferred habitat and you should seek them in the shallower waters.

“Off Southern California, upwelling, which brings close to shore deep water that is low in temperature and oxygen and high in salinity, causes dramatic changes in the distribution patterns of inshore the fishes. Seasonal changes less dramatic than upwelling also have a profound effect on the soft-bottomed fish fauna.—Peter B. Moyle and Joseph J. Cech, Fishes: An Introduction to Ichthyology

PFIC—Remember too that in some ways fish are like humans. A quick change in weather conditions will often put fish “off their feed” for a couple of days; they will not seem to bite as well and there is little the angler can do. Why this happens is unclear but scientists now know that fish are extremely sensitive to changes in temperature. In fact, some fish can detect changes as little as 1/50 of a degree Fahrenheit in temperature, sensitivity unmatched by any warm-blooded animals. And, since fish are cold-blooded creatures, their metabolism slows down with a drop in water temperature. A change in water temperature does not always mean a decrease in the quality of fishing but often times that is the result—at least for a few days.
Unlike humans who are warm blooded and maintain a constant 98.6 degree body temperature, fish are cold blooded and their bodies adjust to match the water they are in. As a result, their metabolism can change drastically depending upon the temperature of the water. Typically when a fish experiences a decrease in water temperature (especially if less than it is used to), it will become lethargic, eat less and move around less. If the water shows a drastic drop in temperature, the fish may almost cease to eat altogether. Although every fish is different, some preferring warm water, and some cold water, the change to their preferred water temperature is one key to their behavior. It also explains why warmer weather (and water temperatures) often sees an increase in fish activity and fishing success.
Temperature is also one of the main signals for fish to spawn. A prime example is barred surfperch, which in southern California typically spawn during the winter months. In some areas, concentrations of the fish show up ready to spawn in December. In other areas, it may be a few weeks or a few months later. Water temperature is the critical factor, and a variance of only a few degrees signals the start, stop, or restart of spawning behavior. Up north, in Mendocino County, you can generally count on May 1 as being the time local estuaries become populated by swarms of striped seaperch. If water temperature warms earlier, the spawning may begin in April. If water is a little colder, the spawn may start several weeks late. Since times of spawning are one of the best times to fish, due to the concentrations of the fish, water temperature records should also be kept and used as guidelines once ideal temperatures are established.

A clue to one of the great mysteries of marine life—the migrations of fish—may be found in the behavior of one of the clam’s near relatives, the mussel. The bay mussel, a black-shelled mollusk which clamps itself firmly to rocks or pilings, is a species distinct from those outside the Gate, and its spawn forms one of the most important food sources for the bay’s fish. In the spring, influenced by unknown forces-possibly changes in the bay's salinity or temperature-it throws out vast quantities of cells called gametes, which combine to form the mussel larvae. Biologists speculate that this great seasonal larva production of the mussels may determine in some degree the migrations of the fish which depend upon on it for food. —Harold Gilliam, San Francisco Bay, 1957