Morphology

Pacific sardines are elongated pelagic fish known to form large dense schools near the ocean surface – a behavior that helps protect them from predators. They use their large eyes and excellent eyesight to locate dense patches of prey in the water. Most individuals are under 30 centimeters in length, but some can get to be over 40 centimeters. This elegant fish uses countershading to camouflage itself from predators above them in the water column. Countershading entails blue-green coloring from above, and silver bellies underneath.

Habitat and Range

Pacific sardines inhabit coastal waters as well as open ocean environments. They are found in the Indo-Pacific and East Pacific oceans and the Gulf of California. The distribution of Pacific sardines is closely tied to sea surface temperatures. During warmer periods, sardines expand their range northward, reaching as far as British Columbia, Canada. Conversely, during cooler periods, their range contracts, and they are seldom found north of Point Conception, California.

Range Map

Reproductive Biology and Life History

Pacific sardines can live up to 13 years, although most do not surpass 5 years of age. They grow rapidly and can reach lengths of over 30 centimeters. Sardines reproduce by their second year and spawn multiple times per season. Females release up to 45,000 eggs per spawning event, which are fertilized externally in the water column.

Ecology

Pacific sardines are a crucial forage species in the California Current Ecosystem, transferring energy from lower to higher trophic levels. They serve as a significant food source for many marine mammals, fish, seabirds, and pelagic invertebrates. Historically, sardine populations have exhibited cyclical fluctuations over approximately 60-year periods, which are believed to be linked to changes in oceanic conditions, particularly temperature. Sardines undertake seasonal migrations along the Pacific coast, moving to feeding grounds in the north during summer and returning to spawning grounds in the south during winter. These migrations are closely tied to environmental conditions and the availability of food resources.

Culture and Historical Context

Pacific sardines supported the largest commercial fisheries in the western hemisphere in the 1920s to 1940s, peaking at over 700,000 metric tons harvested per year. At its peak, the sardine fishery played an important role in California coastal economy, with “Cannery Row” in Monterey, California, made famous by John Steinbeck, representing the legacy of this now collapsed fishery. The population decline was so severe – that at its low point it was estimated that sardines had declined to a spawning biomass of only 10,000 metric tons. The population has never recovered to its historical peak levels but did recover enough to be harvested again in 1999 before experiencing another collapse – a 95% decline from 2006 until 2017.