| Summary: | Anchovies are species of ecological and economic importance that inhabit coastal waters, where they are very abundant. The objective of the study was, through high-frequency temporal sampling, to analyze the diversity, seasonal and diel distribution patterns of anchovies and their relationships with environmental variables. For 19 months, 24-h monthly cycles were carried out, taking samples every two hours. Permutational analysis of variance (PERMANOVA) and redundancy analysis (RDA) were used for data analysis. Seven species were captured, of which, <i>Anchoa mitchilli</i>, <i>Anchoa hepsetus</i>, <i>Anchoa lyolepis</i>, <i>Anchoa lamprotaenia</i> and <i>Cetengraulis edentulus</i> are common in brackish waters; however, <i>Anchoviella perfasciata</i> and <i>Engraulis eurystole</i> rarely occur in these systems. For these species, no major threats are known; therefore, they are listed as ‘Least Concern’. A seasonal succession shows pulses during the closed-mouth phase and during the late warm-rainy season. At diel level, <i>A. mitchilli</i>, <i>C. edentulus</i> and <i>A</i>. <i>lamprotaenia</i> showed a markedly nocturnal pattern. RDA correlations showed that salinity, day/night effect, inlet state and rainfall were the most important factors related to anchovy distribution. Segregation along a salinity gradient was observed, in which <i>A</i>. <i>mitchilli</i> was captured mainly at low salinities, while other species occurred mainly at intermediate to high salinities. High-frequency sampling allowed a better understanding of the species richness and abundance patterns of anchovies in the system.
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