Distribution of whitemouth croaker (Micropogonias furnieri, Desmarest 1823) larvae in the Río de la Plata estuarine front |
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| Authors: | Mara S Braverman E Marcelo Acha Domingo A Gagliardini Martín Rivarossa |
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| Institution: | 1. Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Paseo Victoria Ocampo No 1, P.O. Box 175, B7602HSA Mar del Plata, Argentina;2. Universidad Nacional de Mar del Plata (UNMdP), Funes 3250, Mar del Plata, Argentina;3. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Rivadavia 1917, 1033 Buenos Aires, Argentina;4. Instituto de Astronomía y Física del Espacio (CONICET), Pabellón IAFE, Ciudad Universitaria, 1428 Buenos Aires, Argentina;5. Centro Nacional Patagónico (CONICET), Boulevard Brown S/N, U9120ACV Puerto Madryn, Chubut, Argentina |
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| Abstract: | Whitemouth croaker (Micropogonias furnieri) larvae obtained and hydrographic data collected in the Rio de la Plata estuary (35°S–56°W) between 1987 and 2000 were used to explore the early life stages spatial and temporal distribution patterns and their relation to oceanographic features. The spatial distribution, restricted to a band in the inner part of the estuary, coincided with the bottom salinity front and the maximum turbidity zone (MTZ, turbidity front). Larvae were present during the warmest months (October through May) within a range of 14–24.5 °C temperature and 0.9–33 salinity. A vertically stratified sampling performed in the region where the largest abundance was found (December 2005 and March 2006) was used to test the hypothesis that larvae retention occurs in the bottom salinity front.The vertically stratified sampling showed larvae throughout the water column with high predominance in the river–estuary transition zone. A positive correlation between abundance and the bottom salinity horizontal gradient was found. The size analysis showed that the largest individuals (>10 mm SL), probably undergoing the settlement process, inhabited near the bottom and that the smallest (<10 mm SL) were present in the whole water column. Length distribution along the front showed no trend.Results support the estuarine retention hypothesis of previous studies on whitemouth croaker gravid females, eggs distribution and outcomes from a numerical simulation model. Retention in the salinity front/MTZ would allow larvae to benefit from food accumulation in the region, the high turbidity level provide shelter against predators and retention in the estuary secure closeness to the main nursery ground. |
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| Keywords: | Sciaenids fish larvae salinity front turbidity front larvae retention Rí o de la Plata estuary (35° S– 56° W) |
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