Sardinops sagax caerulea
Family: CLUPEIDAE (Herrings and Sardines)
Sardines are small silvery fishes with a single dorsal fin located over the middle of the body, a forked caudal fin and a keel of large spiny scales along the belly. S. sagax caerulea exhibits widely scattered dark spots along the sides. Radiating stria on the operculum distinguishes this species from other members of this family in the region. They grow to 38 cm (14 inches) long.
Range and Habitat
Range: During times of high abundance (from the early part of the 20th century into the 1940s) this species ranged from the Gulf of California north to southeastern Alaska. After the 1950s it virtually disappeared from the region north of Point Conception. In this period of lowered abundance, which persisted through the mid-1980s, the population was centered off central and southern Baja California. High abundances were noted in the Gulf of California in the early 1970s and have supported a major fishery there since then. The population began a noticeable recovery off southern and central California in the mid to late 1980s and by the early 1990s began appearing in small numbers off British Columbia. The population appears to have reestablished itself throughout its original range as of the mid to late 1990s. Sardinops sagax caerulea is thought to be a subspecies of the sardine inhabiting the Peru-Chile Current (Sardinops sagax).
Habitat: Coastal, pelagic (commonly occurs up to 150 miles offshore in times of abundance). Sardines travel in schools that may contain hundreds of thousands to millions of individuals. The large numbers of fish in the schools and their rapid coordinated movements serve as an adaptation against predators. They are migratory and may travel distances of more than 1000 km between feeding and spawning habitats over the course of a year.
Various fishesas well as marine mammals and sea birdsprey on sardines. On Isla Rasa in the central Gulf of California, half a million birds (Heermann's Gulls and Elegant Terns) catch about 65 tons of sardines each day during three months of the nesting season. Sardines feed on zooplankton and phytoplankton by filter feeding and selective capture of larger prey. Life span under natural conditions is normally 12 to 13 years, but some are thought to live up to 20 to 25 years. Spawning may occur in the first year. Eggs are pelagic. Studies of a 1500-year long record of deposition of sardine scales in a well preserved sedimentary deposit off the coast of southern California indicate that this species has undergone natural fluctuations of high and low abundance varying in length between 50 to 75 years, apparently related to large-scale climate change.
This species was fished to the point of commercial extinction off California under high demand for fish meal and oil and for canned products for direct human consumption. The development of the sardine fishery followed a now familiar pattern of rapid growth and then accelerating decline seen in virtually all fisheries based on small pelagic fish around the world. This pattern is exemplified in the collapse of the massive anchovy fishery off Peru. The Pacific population of Sardinops sagax caerulea collapsed in the early 1960s under heavy exploitation off California, combined with loss of habitat brought on by climate change with cooler waters in the eastern North Pacific. A major fishery based on Sardinops s. was developed in the Gulf of California during the 1970s and has persisted to the present, although drastically reduced catches during several years in the 1990s have raised concern among Mexican fisheries scientists. The population began to recover off California in the 1980s under protection from a fishing moratorium in place since 1967, and with improved habitat conditions due to a return to more favorable ocean conditions. This population now supports a modest fishery off Baja California and off California. The five species and subspecies of Sardinops yield roughly one-fourth of the catch of all clupeoid fishes, making it one of the most productive of all clupeoid genera. This is exceeded only by the Peruvian anchoveta during its periods of high abundance.
A program of ocean monitoring in the southern region of the California Currentoff Baja Californiahas been underway since Autumn, 1997. This is an interdisciplinary study undertaken by a consortium of six Mexican research institutions known collectively as IMECOCAL (Investigaciones Mexicanas de la Corriente de California). This study is modelled after the CalCOFI (California Cooperative Oceanic Fisheries Investigation) program that was begun in 1951 out of concern over the decline of the sardine in the California Current. CalCOFI continues to monitor ocean conditions off California every three months and is renowned as one of the most enduring and productive programs for the study of pelagic ecosystems in the world's ocean. The IMECOCAL program of seagoing observations is coordinated with CalCOFI to provide the coverage needed to match the spatial scale of scientific sampling and analysis to the natural scale of variability in the California Current system. This scientific collaboration between Mexico and the United States is also providing information needed to understand the migratory behavior and natural history of transboundary pelagic species like Sardinops sagax caerulea inhabiting both the waters off Mexico and the United States. The long-term goal of IMECOCAL is to improve our capability to predict the response of the pelagic ecosystem to regional and global climate change, as well as to the combined effects of harvesting practices by Mexico and the United States.
Text by Dr. Timothy Baumgartner, Scripps Institution of Oceanography and CICESE
and Patricia Beller, San Diego Natural History Museum
Photograph © 2000 Gini Kellogg
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