The Rio de Ia Plata Estuary, Argentina-Uruguay
195
13.3.3.3 Nekton
The stripped weakfish Cynoscion guatucupa, with nursery grounds in
coastal areas around the estuary, as well as Umbrina canosai, Micropogonias
furnieri, and Macrodon ancylodon are abundant sciaenids in marine environments down to 50 m depth. Paralichthys patagonicus is the most
abundant flatfish ( Cousseau 1985). Other flatfishes are Xystreuris rasile, the
small sole Symphurus jennynsi, and Paralichthys isosceles, which occurs in
deeper waters (>50 m). Dominant species on rocky bottoms (<50 m), mainly along the coast of Argentina, are Discopyge tschudii, Cheilodactylus bergi,
Percophis brasiliensis (Percophididae), Pseudopercis semifasciata (Lasta et
al. 1998), as well as Acanthistius brasilianus and the red porgy Sparus pagrus. The feeding habits of Sparus pagrus and hawkfish ( Cheilodactylus bergi) are related to the composition and structure of benthic feeding grounds
(Brankevich et al.1990; Bruno et al. in press). Percophis brasiliensis, Porichthys porosissimus (Batrachoididae), and Prionotus punctatus occur in
marine waters (35-m depth) but may also be found in estuarine areas. The
most abundant elasmobranch is Mustelus schmitii, followed by M. canis, M.
fasciatus, and Galeorhinus vitaminicus. Myliobatiformes (Myliobatis goodei, Dasyatis pastinaca), Rhinobatiformes (Zapterix brevirostris), Hexanchiformes (Notorhinchus pectorosus), and Squatiniformes (Squatina argentina) are also common in shelf waters (Cousseau 1985). Among pelagic
species, the anchovy Engraulis anchoita (Engraulidae) is abundant, followed by Trachurus lathami and Parona signata (Carangidae), which also
enter mixohaline waters, and Stromateidae (Stromateus brasiliensis, Peprilus paru). Pomatomus saltatrix, Scomber japonicus, Thyrsitops lepidopodea,
and Trichiurus lepturus reach coastal and mixohaline areas in summer,
while Balistes capriscus (Tetraodontiformes) sporadically occurs during fall
(Nion and Rios 1991).
13.3.3.4 Mammals
The sea lion Otaria flavescens inhabits rocky or sandy areas and mainly
hunts in coastal waters (Vaz-Ferreira and Ponce de Leon 1984), while the
South American fur seal Arctocephalus australis lives on steep rocky habitats and feeds in deep shelf areas. Both species feed on fish ( Cynoscion guatucupa, Micropogonias furnieri, Macrodon ancylodon, Porichthys porossisimus, Paralonchurus brasiliensis), squid (Loligo spp.), and shrimps but are
preyed upon by some sharks and the killer whale Orcin us orca.
195
13.3.3.3 Nekton
The stripped weakfish Cynoscion guatucupa, with nursery grounds in
coastal areas around the estuary, as well as Umbrina canosai, Micropogonias
furnieri, and Macrodon ancylodon are abundant sciaenids in marine environments down to 50 m depth. Paralichthys patagonicus is the most
abundant flatfish ( Cousseau 1985). Other flatfishes are Xystreuris rasile, the
small sole Symphurus jennynsi, and Paralichthys isosceles, which occurs in
deeper waters (>50 m). Dominant species on rocky bottoms (<50 m), mainly along the coast of Argentina, are Discopyge tschudii, Cheilodactylus bergi,
Percophis brasiliensis (Percophididae), Pseudopercis semifasciata (Lasta et
al. 1998), as well as Acanthistius brasilianus and the red porgy Sparus pagrus. The feeding habits of Sparus pagrus and hawkfish ( Cheilodactylus bergi) are related to the composition and structure of benthic feeding grounds
(Brankevich et al.1990; Bruno et al. in press). Percophis brasiliensis, Porichthys porosissimus (Batrachoididae), and Prionotus punctatus occur in
marine waters (35-m depth) but may also be found in estuarine areas. The
most abundant elasmobranch is Mustelus schmitii, followed by M. canis, M.
fasciatus, and Galeorhinus vitaminicus. Myliobatiformes (Myliobatis goodei, Dasyatis pastinaca), Rhinobatiformes (Zapterix brevirostris), Hexanchiformes (Notorhinchus pectorosus), and Squatiniformes (Squatina argentina) are also common in shelf waters (Cousseau 1985). Among pelagic
species, the anchovy Engraulis anchoita (Engraulidae) is abundant, followed by Trachurus lathami and Parona signata (Carangidae), which also
enter mixohaline waters, and Stromateidae (Stromateus brasiliensis, Peprilus paru). Pomatomus saltatrix, Scomber japonicus, Thyrsitops lepidopodea,
and Trichiurus lepturus reach coastal and mixohaline areas in summer,
while Balistes capriscus (Tetraodontiformes) sporadically occurs during fall
(Nion and Rios 1991).
13.3.3.4 Mammals
The sea lion Otaria flavescens inhabits rocky or sandy areas and mainly
hunts in coastal waters (Vaz-Ferreira and Ponce de Leon 1984), while the
South American fur seal Arctocephalus australis lives on steep rocky habitats and feeds in deep shelf areas. Both species feed on fish ( Cynoscion guatucupa, Micropogonias furnieri, Macrodon ancylodon, Porichthys porossisimus, Paralonchurus brasiliensis), squid (Loligo spp.), and shrimps but are
preyed upon by some sharks and the killer whale Orcin us orca.