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The Peru-Chile eastern Pacific fisheries and climatic oscillation

César N. Caviedes and Timothy J. Fik

Department of Geography

University of Florida Gainesville, FL 32611, USA

There is little doubt that the fisheries of the Humboldt (Peru) Current (Fig. 15.1) represent the largest in the world, not only if one considers the primary production (Paulik, 1971) and catch potential of its waters (Sharp, 1987), but also in view of record-setting catches. During the 1960s and early 1970s, these catches comprised nearly 20 percent of the world's landings (Fig. 15.2). Yet, the Humboldt Current that supported such high volumes of fish and nourished an enormous marine ecosystem has been constantly beset by oceanic-climatic oscillations - known as El Niño-Southern Oscillation (ENSO) - that noticeably depressed biological productivity and yield levels.

There have also been ecological perturbations in the historical or geological past, as documented in the pioneering work of Schweigger (1959) which offers revealing details of fish, bird, and mammal mortality resulting from pre-1972 El Niño events. DeVries (1987) also provides information about geological findings that hint at past catastrophic perturbations along the western coast of South America. Recent ENSO events have resulted in remarkable variations of fish production in the coastal waters of Peru and Chile, measured in terms of fish landings and biomass estimations. It is certain that the depressed Peruvian catches since 1972 reflect the simultaneous occurrence of overfishing and El Niño (Instituto del Mar del Perú, 1981).

Considering the intensity of ENSO events in recent times, particularly in 1972-73 and 1982-83, a dominating thought has begun to develop among ecologists and earth scientists that ascribes to changing global environmental conditions the marked changes in primary productivity and fish population levels that have occurred in eastern boundary current fisheries (see Sharp, 1987; Steele, io°s

30"S

Fig. 15.1 Major fishing ports and biological production areas along the coasts of Peru and Chile.

Fig. 15.1 Major fishing ports and biological production areas along the coasts of Peru and Chile.

YEAR

Fig. 15.2 Southeast Pacific fisheries output, 1951-86.

YEAR

Fig. 15.2 Southeast Pacific fisheries output, 1951-86.

1989). This hypothesis, although supported by some initial climatic/oceanic indicators, requires additional testing in order to verify the assumption of a secular change of oceanic-climatic conditions in the Humboldt Current system.

A first step, when proposing that the dwindling fisheries of Peru and Chile are related to oceanic-climatic changes, is to determine

PERU

Pu«rto Chicomo I Coishco fV Chimbóte

V Casma \ Huarmey V Supe

Vegueta Chancay Tambo de Moro 'Piteo i BOLIVIA

Atico

Iquique

Tocopilla

CHILE

Antofagatta

Taltal, ChaJTaral/

Colderb

84"W 80"W 76 "W 72"W 68"W

whether a steady change of conditions has occurred. It could be that only a long-term fluctuation, by no means of permanent character, has upset the system during the last decade and that reduced fishery capacity is a reversible situation. The collapse of the anchovy fisheries in the waters of Peru and Chile and the surrounding circumstances, other than just the oceanic-climatic variables, must also be carefully assessed. In this sense, the study of time series of catches illustrating the dramatic growth of the eastern tropical Pacific pelagic fisheries during the 1950s and 1960s might uncover disruptive processes which may not have been entirely induced by nature. An answer to a third question to be addressed requires the availability of a long time series to check if we might not perhaps be witnessing the short segment of a biological cycle with a long periodicity in some pelagic species, the total effect of which cannot be uncovered using short time series (i.e., from the mid-1950s to the present). Research suggests the existence of natural cycles greater than 50 years in the abundance of Pacific clupeids (Kawasaki, 1983; Sharp et al., 1984; see also Kawasaki, this volume). Therefore, the possibility that the contraction of some species may possibly originate from these cycles and not from irreversible environmental changes cannot be ruled out.

Using statistical methods, this chapter examines the trends of Peruvian and Chilean fisheries since the introduction of industrial fishing activities. The procedure allows for the recognition of models that can be fitted to that growth and reveals the existence of natural events ("interventions") that may have affected the observed trends. A similar treatment is applied to available oceanic and meteorological data to detect periodicities, changes, or oscillations that might account for the dwindling fish stocks.

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