The Maracaibo System, Venezuela
55
zuloagai in June. Seaward migrations of these species initiate in April and
last until September. Among the freshwater ichthyofauna ( 113 species), Siluriformes predominate and about 40 species are endemic to rivers in the Maracaibo Basin (Perez Lozano and Taphorn 1993). Several species of theCatatumbo River display an annual migratory cycle ( Galvis et al. 1997) that
parallels maximum river discharge in April-May and September-November. Fish populations feed and reproduce in the productive lowland swamps
and initiate their upriver migration when freshwater runoff decreases.
Five species of Cetacea have been recorded from the Gulf of Venezuela
and other vertebrates like Cayman sclerops fuscus and Crocodylus acutus
occur at the mouth of rivers at the southern lake coast. The freshwater dolphin Sotalia fluviatilis is a common visitor of the lake and the strait, but the
manatee Trichechus manatus has only been cited once (Agudo et al. 1994).
The west coast of Tablazo Bay is the only nesting site of the flamingo Phoenicopterus ruber in Venezuela.
3.4 Production Processes
Primary production in the outer gulf shows considerable fluctuations,
though pigment concentrations are consistently high (0.5 mg m- 3 ) in upwelling areas at the southeastern coast (Gines 1982; Miiller-Karger et al.
1989). In Tablazo Bay and the strait, primary production follows a bimodal
distribution with maximum productivity (5.56 g C per m 2 and day) in
March (Rodriguez and Conde 1989). Total chlorophyll a concentrations in
lake surface waters vary between 13 and 45 jlg 1- 1 (1-3 g C per m 2 and day)
and tend to decrease at depths between 10 and 25m, except in areas around
the Catatumbo River mouth (14 jlg 1- 1 ; Parra Pardi 1979). At the northeastern side of the lake, where oil production concentrates, chlorophyll a
(223 jlg 1- 1 ) and primary productivity (10.5 g C per m 2 and day) may reach
elevated levels (Battelle 1974; Rodriguez and Conde 1989). The visible
effect of high productivity in the lake is the formation of algal surface
blooms, which suggests a process of eutrophication despite the occurrence
of blooms since 1937 (Escam 1991).
Similar to phytoplankton, zooplankton follows large temporal and spatial fluctuations in the Gulf of Venezuela. Dense populations of tunicates,
especially Salpa democratica, occur in March and August and larval forms
of Lucifer faxoni may represent 80% of the community (Rodriguez 1973;
Gines 1982). Biomass in the gulf varies between 3 and 63 mg m- 3 , with a
maximum in August ( 120 mg m- 3 ). Lower zooplankton biomass in the center of the gulf may be due to the deflection of nutrient-rich waters toward
55
zuloagai in June. Seaward migrations of these species initiate in April and
last until September. Among the freshwater ichthyofauna ( 113 species), Siluriformes predominate and about 40 species are endemic to rivers in the Maracaibo Basin (Perez Lozano and Taphorn 1993). Several species of theCatatumbo River display an annual migratory cycle ( Galvis et al. 1997) that
parallels maximum river discharge in April-May and September-November. Fish populations feed and reproduce in the productive lowland swamps
and initiate their upriver migration when freshwater runoff decreases.
Five species of Cetacea have been recorded from the Gulf of Venezuela
and other vertebrates like Cayman sclerops fuscus and Crocodylus acutus
occur at the mouth of rivers at the southern lake coast. The freshwater dolphin Sotalia fluviatilis is a common visitor of the lake and the strait, but the
manatee Trichechus manatus has only been cited once (Agudo et al. 1994).
The west coast of Tablazo Bay is the only nesting site of the flamingo Phoenicopterus ruber in Venezuela.
3.4 Production Processes
Primary production in the outer gulf shows considerable fluctuations,
though pigment concentrations are consistently high (0.5 mg m- 3 ) in upwelling areas at the southeastern coast (Gines 1982; Miiller-Karger et al.
1989). In Tablazo Bay and the strait, primary production follows a bimodal
distribution with maximum productivity (5.56 g C per m 2 and day) in
March (Rodriguez and Conde 1989). Total chlorophyll a concentrations in
lake surface waters vary between 13 and 45 jlg 1- 1 (1-3 g C per m 2 and day)
and tend to decrease at depths between 10 and 25m, except in areas around
the Catatumbo River mouth (14 jlg 1- 1 ; Parra Pardi 1979). At the northeastern side of the lake, where oil production concentrates, chlorophyll a
(223 jlg 1- 1 ) and primary productivity (10.5 g C per m 2 and day) may reach
elevated levels (Battelle 1974; Rodriguez and Conde 1989). The visible
effect of high productivity in the lake is the formation of algal surface
blooms, which suggests a process of eutrophication despite the occurrence
of blooms since 1937 (Escam 1991).
Similar to phytoplankton, zooplankton follows large temporal and spatial fluctuations in the Gulf of Venezuela. Dense populations of tunicates,
especially Salpa democratica, occur in March and August and larval forms
of Lucifer faxoni may represent 80% of the community (Rodriguez 1973;
Gines 1982). Biomass in the gulf varies between 3 and 63 mg m- 3 , with a
maximum in August ( 120 mg m- 3 ). Lower zooplankton biomass in the center of the gulf may be due to the deflection of nutrient-rich waters toward