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J. Tarazona and W. Arntz
sandy beaches are large-sized species such as the ghost crab Ocypode gaudichaudii, the mole crab Emerita analoga, and the surf clams Mesodesma
donacium and Donax marincovichi. The exposed sandy beaches of the
Peruvian central coast reveal exceptionally high faunal density (up to
10,000 ind. m- 2 ) and biomass (up to 35,500 g wet weight m- 2 ) as a consequence of the extremely high water column productivity (Rowe 1985).
Elevated organic matter accumulation and high H 2 S content (Rowe
1985; Arntz et al. 1991) of the Peruvian coastal upwelling ecosystem
beyond 50 m depth induce hypoxic ( <0.5 mll- 1 ) or anoxic conditions and
lead to a benthic community with low diversity and high dominance of
only a few species. These conditions favor high biomass (> 1,000 g wet
weight m- 2 ) of giant filamentous bacteria (Thioploca araucae, T. chileae;
Gallardo 1977) which link nitrogen and sulfur cycles in the sediment (Fossing et al. 1995). At lower depths and closer to the coast sulfide-rich sediments(> 1,200 M) are dominated by different species of the giant filamentous bacteria Beggiatoa. Since benthic diversity follows an oxygen-related
gradient, the species number and density of deeper benthic communities
tend to increase along the continental shelf from the south to the north and
during El Nino events, when the benthic system is flushed with high dissolved oxygen concentrations (Fig. 16.2; Arntz et al. 1991).
16.3.4 Fishes and Other Vertebrates
The high productivity of the Peruvian upwelling causes low diversity
among pelagic and demersal ichthyofauna with elevated densities of some
epipelagic and mesopelagic species. The dominant coastal water fishes are
pilchard (Sardinops sagax) and anchovy (Engraulis ringens), of which the
latter has been the dominant species in this ecosystem for at least
12,000 years (DeVries and Pearcy 1982). The jack mackerel (Trachurus picturatus murphii) and Pacific mackerel (Scomber japonicus) are common
along the shelf margin and mesopelagic species of the outer upwelling system are largely represented by lantern fishes such as Vinciguerria lucetia.
The Peruvian pelagic anchovy fishery initiated in the early 1950s reached
annual landings of about 12.5 million tons in the early 1970s, followed by a
sharp decline as a result of overfishing and due to the 1972-1973 El Nino impact. Although fisheries recovered, landings are much lower than in the
1970s (Pauly and Tsukayama 1987; Pauly et al. 1989). During the last decades, anchovy and pilchard have experienced considerable fluctuations
and alternating patterns off Peru, with dominance of anchovy in cold La
Nifia and dominance of pilchard in warm El Nino years (Niquen et al. 1999).
Oceanic species such as yellowfin tuna ( Thunnus albacares) and giant squid
(Dosidicus gigas) also sustain important fisheries.
J. Tarazona and W. Arntz
sandy beaches are large-sized species such as the ghost crab Ocypode gaudichaudii, the mole crab Emerita analoga, and the surf clams Mesodesma
donacium and Donax marincovichi. The exposed sandy beaches of the
Peruvian central coast reveal exceptionally high faunal density (up to
10,000 ind. m- 2 ) and biomass (up to 35,500 g wet weight m- 2 ) as a consequence of the extremely high water column productivity (Rowe 1985).
Elevated organic matter accumulation and high H 2 S content (Rowe
1985; Arntz et al. 1991) of the Peruvian coastal upwelling ecosystem
beyond 50 m depth induce hypoxic ( <0.5 mll- 1 ) or anoxic conditions and
lead to a benthic community with low diversity and high dominance of
only a few species. These conditions favor high biomass (> 1,000 g wet
weight m- 2 ) of giant filamentous bacteria (Thioploca araucae, T. chileae;
Gallardo 1977) which link nitrogen and sulfur cycles in the sediment (Fossing et al. 1995). At lower depths and closer to the coast sulfide-rich sediments(> 1,200 M) are dominated by different species of the giant filamentous bacteria Beggiatoa. Since benthic diversity follows an oxygen-related
gradient, the species number and density of deeper benthic communities
tend to increase along the continental shelf from the south to the north and
during El Nino events, when the benthic system is flushed with high dissolved oxygen concentrations (Fig. 16.2; Arntz et al. 1991).
16.3.4 Fishes and Other Vertebrates
The high productivity of the Peruvian upwelling causes low diversity
among pelagic and demersal ichthyofauna with elevated densities of some
epipelagic and mesopelagic species. The dominant coastal water fishes are
pilchard (Sardinops sagax) and anchovy (Engraulis ringens), of which the
latter has been the dominant species in this ecosystem for at least
12,000 years (DeVries and Pearcy 1982). The jack mackerel (Trachurus picturatus murphii) and Pacific mackerel (Scomber japonicus) are common
along the shelf margin and mesopelagic species of the outer upwelling system are largely represented by lantern fishes such as Vinciguerria lucetia.
The Peruvian pelagic anchovy fishery initiated in the early 1950s reached
annual landings of about 12.5 million tons in the early 1970s, followed by a
sharp decline as a result of overfishing and due to the 1972-1973 El Nino impact. Although fisheries recovered, landings are much lower than in the
1970s (Pauly and Tsukayama 1987; Pauly et al. 1989). During the last decades, anchovy and pilchard have experienced considerable fluctuations
and alternating patterns off Peru, with dominance of anchovy in cold La
Nifia and dominance of pilchard in warm El Nino years (Niquen et al. 1999).
Oceanic species such as yellowfin tuna ( Thunnus albacares) and giant squid
(Dosidicus gigas) also sustain important fisheries.