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J. Tarazona and W. Arntz
further north or offshore occur in coastal waters off central Peru and northern Chile. Demersal fish catches off Peru decreased by about 60%
because fish shoals dispersed and moved into deeper waters (i.e., hake
below 1000 m) but nearly doubled off Chile (56,000-71,000 tons in
1982-1983), probably due to southward migration of part of the demersal
stocks (Espino 1999). The limited food resources (i.e., anchovy populations) during strong El Nino events force fur seals, sea lions, and guano
birds to migrate further south. The extension of offshore feeding excursions and dives to greater depths has led to high mortality of sea lions
(50% of newborn) and fur seals (almost 100% of newborn) along the
southern coast of Peru.
16.5 Need for Cautious Management
The peculiar structure and dynamics of the Peruvian coastal upwelling
ecosystem make it one of the most productive marine systems worldwide.
Owing to the immense natural nutrient input via upwelling and nutrient
enrichment of waters around islands and capes by guano bird colonies, the
assimilation of additional human-derived eutrophication is likely to be
limited because areas of well-oxygenated shallow coastal water are extremely narrow. Despite both the extraordinary productive capacity (landings occasionally over 12 million tons year- 1 ) and resilience (recovery
from anchovy overfishing and other resources; Arntz 1986; Alheit and Bernal1993), coastal fishery resources have limited capacity for exploitation.
Warm and cold El Nino and La Nina events add to the high variability of
the Peruvian upwelling ecosystem and further changes may be expected
due to global warming. Therefore, an interdisciplinary approach for the
comprehension of ecosystem functioning is necessary and monitoring
programs and simulation models should be established to serve as a base
for regulation of human activities and sustained exploitation. Despite
some success in the 1980s (Pauly and Tsukayama 1987; Pauly et al. 1989;
Jarre-Teichmann 1998) and recent progress in real time registration of El
Nino and La Nina events by satellites and extended drift buoy systems, a
holistic management approach has yet to be implemented for this upwelling ecosystem.
Acknowledgements. This work was supported by a grant from the Alexander von Humboldt Foundation to the first author during his sabbatical year at the Alfred Wegener
Institute in Bremerhaven, Germany. We are grateful to the DePSEA Research Group, in
particular Sonia Valle and Nora Malca. AWl contribution no. 1777.
J. Tarazona and W. Arntz
further north or offshore occur in coastal waters off central Peru and northern Chile. Demersal fish catches off Peru decreased by about 60%
because fish shoals dispersed and moved into deeper waters (i.e., hake
below 1000 m) but nearly doubled off Chile (56,000-71,000 tons in
1982-1983), probably due to southward migration of part of the demersal
stocks (Espino 1999). The limited food resources (i.e., anchovy populations) during strong El Nino events force fur seals, sea lions, and guano
birds to migrate further south. The extension of offshore feeding excursions and dives to greater depths has led to high mortality of sea lions
(50% of newborn) and fur seals (almost 100% of newborn) along the
southern coast of Peru.
16.5 Need for Cautious Management
The peculiar structure and dynamics of the Peruvian coastal upwelling
ecosystem make it one of the most productive marine systems worldwide.
Owing to the immense natural nutrient input via upwelling and nutrient
enrichment of waters around islands and capes by guano bird colonies, the
assimilation of additional human-derived eutrophication is likely to be
limited because areas of well-oxygenated shallow coastal water are extremely narrow. Despite both the extraordinary productive capacity (landings occasionally over 12 million tons year- 1 ) and resilience (recovery
from anchovy overfishing and other resources; Arntz 1986; Alheit and Bernal1993), coastal fishery resources have limited capacity for exploitation.
Warm and cold El Nino and La Nina events add to the high variability of
the Peruvian upwelling ecosystem and further changes may be expected
due to global warming. Therefore, an interdisciplinary approach for the
comprehension of ecosystem functioning is necessary and monitoring
programs and simulation models should be established to serve as a base
for regulation of human activities and sustained exploitation. Despite
some success in the 1980s (Pauly and Tsukayama 1987; Pauly et al. 1989;
Jarre-Teichmann 1998) and recent progress in real time registration of El
Nino and La Nina events by satellites and extended drift buoy systems, a
holistic management approach has yet to be implemented for this upwelling ecosystem.
Acknowledgements. This work was supported by a grant from the Alexander von Humboldt Foundation to the first author during his sabbatical year at the Alfred Wegener
Institute in Bremerhaven, Germany. We are grateful to the DePSEA Research Group, in
particular Sonia Valle and Nora Malca. AWl contribution no. 1777.