170
U. Seeliger
nearshore waters also coincide with increased abundance of their eggs and
larvae in the estuarine plankton community. Nevertheless, most of the eggs
( 88%) and larvae ( 66%) belong to the Clupeidae (i.e., Brevoortia pectinata), Engraulididae (Lycengraulis grossidens), and to the sciaenid Micropogonias furnieri, emphasizing the importance of the estuary as a nursery
ground especially for these species (Sinque and Muelbert 1997).
The migration of more than 100 marine and some freshwater and anadromic fish species into the Patos Lagoon estuary optimizes the abundance
of their populations and hence may significantly contribute to the biological production of the region. The anadromic species Netuma barba and
N. planifrons arrive from the sea to reproduce in pre-limnic zones, after
which the juveniles return to the sheltered conditions and abundant food
of estuarine nursery grounds. Also, the juveniles and sub-adults of marine
species, like the black drum Pogonias cromis, the white croacker Micropogonias furnieri, mullets (Mugil spp.), and the flatfish Paralichthys orbygnianus, are obligatory users of estuary nursery grounds; however, the early
life-cycle stages of most marine species are facultative or they are opportunistic migrators or only enter the estuary occasionally (Chao et al. 1985).
The juveniles of estuarine-dependent marine species and estuarine-resident Atherinidae are most common in shallow waters ( <1.5 m), whilst the
juveniles and/or sub-adults of bottom-oriented epibenthic and demersal
species (i.e., Netuma barba, Micropogonias furnieri, Macrodon ancylodon,
Menticirrhus americanus, Paralonchurus brasiliensis, Cynoscion guatucupa, Umbrina canosai), many of which comprise an important part of the
southern Brazilian landings, are the dominant ichthyofaunal components
of deeper open waters (>4m). Pelagic species are largely represented by
young individuals of Lycengraulis grossidens, Anchoa marinii, Engraulis
anchoita, Trichiurus lepturus, Peprilus paru, Selene setapinis, Brevoortia
pectinata, Ramnogaster arcuata, and Platanichthys platana (Vieira et al.
1998). Since top predators are scarce, the spatial and temporal distribution
patterns of the ichthyofauna are largely a function of salinity distributions
and/or food competition, though bottlenose dolphins (Tursiops truncatus)
and sea lions ( Otaria flavescens) frequently enter the estuary in search of
food.
12.3.2 Unvegetated Subtidal Soft-Bottoms and Intertidal Flats
The soft-bottom of extensive subtidal and intertidal habitats in the estuary
is comprised of unconsolidated sediments which vary with hydrodynamic
energy levels from silty sand in shallow shoals to silty clay in deep channels
(Calliari 1997). The benthic community changes with depth and according
U. Seeliger
nearshore waters also coincide with increased abundance of their eggs and
larvae in the estuarine plankton community. Nevertheless, most of the eggs
( 88%) and larvae ( 66%) belong to the Clupeidae (i.e., Brevoortia pectinata), Engraulididae (Lycengraulis grossidens), and to the sciaenid Micropogonias furnieri, emphasizing the importance of the estuary as a nursery
ground especially for these species (Sinque and Muelbert 1997).
The migration of more than 100 marine and some freshwater and anadromic fish species into the Patos Lagoon estuary optimizes the abundance
of their populations and hence may significantly contribute to the biological production of the region. The anadromic species Netuma barba and
N. planifrons arrive from the sea to reproduce in pre-limnic zones, after
which the juveniles return to the sheltered conditions and abundant food
of estuarine nursery grounds. Also, the juveniles and sub-adults of marine
species, like the black drum Pogonias cromis, the white croacker Micropogonias furnieri, mullets (Mugil spp.), and the flatfish Paralichthys orbygnianus, are obligatory users of estuary nursery grounds; however, the early
life-cycle stages of most marine species are facultative or they are opportunistic migrators or only enter the estuary occasionally (Chao et al. 1985).
The juveniles of estuarine-dependent marine species and estuarine-resident Atherinidae are most common in shallow waters ( <1.5 m), whilst the
juveniles and/or sub-adults of bottom-oriented epibenthic and demersal
species (i.e., Netuma barba, Micropogonias furnieri, Macrodon ancylodon,
Menticirrhus americanus, Paralonchurus brasiliensis, Cynoscion guatucupa, Umbrina canosai), many of which comprise an important part of the
southern Brazilian landings, are the dominant ichthyofaunal components
of deeper open waters (>4m). Pelagic species are largely represented by
young individuals of Lycengraulis grossidens, Anchoa marinii, Engraulis
anchoita, Trichiurus lepturus, Peprilus paru, Selene setapinis, Brevoortia
pectinata, Ramnogaster arcuata, and Platanichthys platana (Vieira et al.
1998). Since top predators are scarce, the spatial and temporal distribution
patterns of the ichthyofauna are largely a function of salinity distributions
and/or food competition, though bottlenose dolphins (Tursiops truncatus)
and sea lions ( Otaria flavescens) frequently enter the estuary in search of
food.
12.3.2 Unvegetated Subtidal Soft-Bottoms and Intertidal Flats
The soft-bottom of extensive subtidal and intertidal habitats in the estuary
is comprised of unconsolidated sediments which vary with hydrodynamic
energy levels from silty sand in shallow shoals to silty clay in deep channels
(Calliari 1997). The benthic community changes with depth and according