194
H. Mianzan et a!.
waters. Eggs and larvae of Brevoortia sp. occur along the Uruguayan coast
under strong influence of Rio de la Plata waters (Hubold and Ehrlich 1981).
Eggs of Trachurus lathami (=picturatus), Prionotus spp., Scomber japonicus, Anchoa marinii, and larvae of Stromateus brasiliensis have been
reported for the Argentine coast (Hubold and Ehrlich 1981; Cassia and
Booman 1985; Sanchez and Ciechomski 1995). Highest concentrations of
eggs and larvae of Cynoscion guatucupa occur in shallow waters near San
Antonio Cape (Cassia and Booman 1985).
13.3.3.2 Benthos
Sandy-gravel bottoms of coastal areas (34-38°S) between 15 and 40 m
depth are typical of invertebrate associations dominated by filter-feeding
mollusks ( Corbula patagonica, Nucula puelcha, Pit aria rostrata) and detritivorous crustaceans (Serolis marplatensis, Pagurus exilis, P. criniticornis,
Ancinus sp.). Deeper bottoms (up to 50 m) also include detritivorous and
predatory echinoderms (Amphiura eugeniae, Astropecten b. brasiliensis,
Patiria stilifer). Shannon species diversity values are 2.69 to 3.58 (C. Bremec and A. Roux, unpubl. data). The detritus-feeding echinoderm Encope
emarginata, the isopod Serolis marplatensis, and coelenterate Renilla sp.
colonies characterize sandy bottoms along the Argentine coast (20-25 m
depth). The species diversity ranges from 1.32 to 2.44. Shrimps (Artemesia
longinaris and Pleoticus muelleri) are common epibenthic species, with
higher densities on fine sand-muddy bottoms (Boschi 1979). Beds of the
commercially valuable clam Mesodesma mactroides occupy medium-fine
sandy beaches along the coasts of Argentina and Uruguay during spring
and summer (Olivier et al.1971; Escofet et al.1979).Associated species are
mollusks (Donax hanleyanus, Buccinanops spp., Olivancillaria spp.), polychaetes ( Glycera americana, Spio gaucha), and isopods (mainly talitrids
and cirolanids). The abundance of commercial-size specimens of M. mactroides has decreased, possibly due to illegal exploitation, tourist activities,
and commercial extraction of sand (Bastida et al. 1991); however, massive
mortality in Brazil, Uruguay, and Argentina (1993-1995) has also been
attributed to a natural phenomenon (J. Carreto, pers. comm.). On rocky
substrates, belts of Chtamalus bisinuatus become denser and the Brachydontes darwinianus-Mytella charruana assemblage is replaced by a
Brachydontes rodriguezi-Mytilus e. platensis assemblage as conditions
become more oceanic (Maytia and Scarabino 1979; Riestra et al. 1992).
H. Mianzan et a!.
waters. Eggs and larvae of Brevoortia sp. occur along the Uruguayan coast
under strong influence of Rio de la Plata waters (Hubold and Ehrlich 1981).
Eggs of Trachurus lathami (=picturatus), Prionotus spp., Scomber japonicus, Anchoa marinii, and larvae of Stromateus brasiliensis have been
reported for the Argentine coast (Hubold and Ehrlich 1981; Cassia and
Booman 1985; Sanchez and Ciechomski 1995). Highest concentrations of
eggs and larvae of Cynoscion guatucupa occur in shallow waters near San
Antonio Cape (Cassia and Booman 1985).
13.3.3.2 Benthos
Sandy-gravel bottoms of coastal areas (34-38°S) between 15 and 40 m
depth are typical of invertebrate associations dominated by filter-feeding
mollusks ( Corbula patagonica, Nucula puelcha, Pit aria rostrata) and detritivorous crustaceans (Serolis marplatensis, Pagurus exilis, P. criniticornis,
Ancinus sp.). Deeper bottoms (up to 50 m) also include detritivorous and
predatory echinoderms (Amphiura eugeniae, Astropecten b. brasiliensis,
Patiria stilifer). Shannon species diversity values are 2.69 to 3.58 (C. Bremec and A. Roux, unpubl. data). The detritus-feeding echinoderm Encope
emarginata, the isopod Serolis marplatensis, and coelenterate Renilla sp.
colonies characterize sandy bottoms along the Argentine coast (20-25 m
depth). The species diversity ranges from 1.32 to 2.44. Shrimps (Artemesia
longinaris and Pleoticus muelleri) are common epibenthic species, with
higher densities on fine sand-muddy bottoms (Boschi 1979). Beds of the
commercially valuable clam Mesodesma mactroides occupy medium-fine
sandy beaches along the coasts of Argentina and Uruguay during spring
and summer (Olivier et al.1971; Escofet et al.1979).Associated species are
mollusks (Donax hanleyanus, Buccinanops spp., Olivancillaria spp.), polychaetes ( Glycera americana, Spio gaucha), and isopods (mainly talitrids
and cirolanids). The abundance of commercial-size specimens of M. mactroides has decreased, possibly due to illegal exploitation, tourist activities,
and commercial extraction of sand (Bastida et al. 1991); however, massive
mortality in Brazil, Uruguay, and Argentina (1993-1995) has also been
attributed to a natural phenomenon (J. Carreto, pers. comm.). On rocky
substrates, belts of Chtamalus bisinuatus become denser and the Brachydontes darwinianus-Mytella charruana assemblage is replaced by a
Brachydontes rodriguezi-Mytilus e. platensis assemblage as conditions
become more oceanic (Maytia and Scarabino 1979; Riestra et al. 1992).