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Peru: Fish Story Linked To Climate Cycle |
| June 16, 2004 |
Source: Vancouver Aquarium Marine Science Centre
By Andy Torr, AquaNews Staff Writer
 | The study has provided further evidence for a link between changes in climate and populations of anchovies (pictured above) and sardines.
Photo: Phil Edgell |
Old fish bones can reveal much more than the diets of people from ages past: they also provide modern-day researchers with clues about the climate in which those people lived. In a new study led by University of Maine scientists, fish bones from an archaeological site in Peru helped to describe Pacific Ocean climate cycles linked to El Nino, the periodic warming of the eastern Pacific that plays havoc with global weather patterns.
The study, published in the scientific journal Quaternary Research, provides new evidence for a theory linking subtle changes in climate to biological cycles in the world's oceans.
In today’s industrial world, the extensive impact of large-scale commercial fishing can make it difficult for scientists to discern the relationship between fish populations and climate. The study points to historical changes in fisheries that pre-date modern commercial fishing, and are thus more likely to be climate-related.
Based on the results of excavations in the ancient village of Lo Demás, just south of modern day Lima, the researchers were able to identify a shift from an abundance of anchovy to an abundance of sardine that took place around 1500 A.D..
The current study extends the El Nino connection back to about 500 years ago at the end of the Inca Empire in Peru. "This strongly suggests that variability in the fisheries had to be linked to the climate; that this was a climate issue rather than a fish harvesting issue," said Dan Sandweiss, an archaeologist at the University of Maine and lead author of the study.
Periodic “Regime Shift”
Over the past century, sardines and anchovies have experienced “boom and bust” cycles that are almost mirror images of each other. When anchovies are abundant, sardines tend to be less abundant, and vice-versa.
Since each species has a different lifecycle and requires different temperature and nutrient conditions, scientists have suggested that Pacific Ocean climate shifts back and forth between a "sardine regime" and an "anchovy regime." Different temperature, circulation and nutrient patterns make the regimes distinct from one another.
Snowfall rates gleaned from glacial ice cores in the Andes revealed that a shift in climate took place around 1500 A.D., approximately the same time as the regime shift identified by the fish bones. The core samples show that the warm phase of the El Nino Southern Oscillation climate cycle contributes to lower snowfall rates. A reduction in anchovies and an increase in sardines also occur in this phase.
A 2003 study by a research team from the Monterey Bay Aquarium Research Institute documented anchovy and sardine harvesting cycles over the past century in Japan, California and Peru. They linked these cycles to climate patterns such as El Nino.
The anchovy-sardine rollercoaster is not the first biological cycle to be linked to climate. Scientists have found similar evidence in ancient corals, tree rings and mollusk shells. Previous reports published in the journal Science have linked changes in mollusk species and even temple-building activities to shifts in the frequency of El Nino.
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