Collapse of Anchovy Fisheries and the Expansion of Sardines In Upwelling Regions

Most of the largest fisheries in the world's oceans are based on small pelagic fish such as anchovy and sardine. These species dominate the ocean in highly productive upwelling regions along the eastern edge of the oceans off California, Peru, Canary Islands, and South Africa and they also occur in other nutrient enriched areas such as off Japan and Argentina. These fisheries have a common pattern of producing huge catches and then collapsing and reappearing 10 to 30 years later. They appear to be inherently unstable populations that expand rapidly in numbers and area when feeding and spawning conditions are favorable, but collapse even more rapidly when ocean conditions change. Within the last century conditions did not stay favorable for any of these populations for periods of more than 30 years. The west coast of South America off Peru and Chile was once the location of the world's largest fishery. Catches of a type of anchovy called anchoveta were above 10 million tons in the late 1960s to 1971 off northern and central Peru. The Peruvian anchovetta population was heavily fished and collapsed during the warming of the 1972 El Niño. The fishery shifted to sardine from 1977 to 1985, and expanded farther south off Chile. Anchovetta off Peru became dominant again in 1986 as waters cooled and sardine declined, but anchovetta started to decline after 1994 and dropped sharply during the 1998 El Niño. The change in locations of the fish populations can have important economic consequences for a country when the fish move out of its territorial waters.

Generalized Locations Click on image to enlarge

Apparent Synchrony in Pacific Basin Sardines Click on image to enlarge

California fisheries for sardine and anchovy have undergone a similar pattern of expansion and collapse in response to changes in ocean climate. Catches of half a million tons of sardine in the late 1930s to mid 1940s disappeared as a colder period began. Anchovy population grew throughout the 1970s but then declined in the 1980s as the area off southern and central California warmed. Pacific sardine slowly increased during the post 1976 warming and expanded their feeding ranges to the north. Older sardine make farther migrations in search of food, but they must be able to return to warmer waters to spawn. During the warmer decades the area suitable for spawning enlarged and extended farther north facilitating the expansion of their population through the 1990s. Pacific mackerel and Pacific whiting, also expanded their feeding area and increased their populations after 1976 but for a shorter period. Both declined after 1988.

These appear to be periods of favorable conditions for one species or the other, perhaps through differences in abundance of types of plankton consumed by each type of fish. Anchovy feed on large zooplankton, whereas sardine feed on phytoplankton and small zooplankton. There are also times when both species of fish are present. Sardine are considered more tropical than anchovy and expand their range poleward in warmer periods. Anchovy do not migrate far seasonally and do not expand far enough poleward during warm regimes to avoid the increased temperatures; they tend to recover during cooler periods. This implies global warming may not produce a proportional shift poleward for all species, but may instead favor the dominance of warmer adapted species over a larger area. (For more information on global synchrony in marine fish populations, see REVIEW OF THE STATE OF WORLD FISHERY RESOURCES: MARINE FISHERIES by the Fishery Resources Division from the United Nations Food and Agriculture Organization, Rome, Italy, go to: http://www.fao.org/docrep/003/w4248e/w4248e00.htm

Pacific Whiting Migration Behavior Click on image to enlarge

TEXT REFERENCES:

	1)	R.A Schwartzlose, et al. 1999. Worldwide Large-scale Fluctuations of Sardine and Anchovy Populations. South African Journal of Marine Science.
		21:289-347.
	2)	Bailey, K., R. Francis, and P. Stevens. 1982. The Life history and Fishery of Pacific Whiting (Merluccius productus).
		CalCOFI Report. 23:81-98.
	3)	M. Dorn. 1995. The Effects of Age Composition and Oceanographic Conditions on the Annual Migration of Pacific Whiting (Merluccius productus).
		CalCOFI Report. 36:97-105.

	Climate Variability & Marine Fisheries Page 4
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