<p>Understanding the influence of local environmental and climatic factors on the abundance of populations is essential for managing natural resources. One climatic phenomenon with global consequences is the <i>El Niño</i> Southern Oscillation (ENSO), which causes excessive rainfall and drought to southern South America during its warm (<i>El Niño</i>) and cold (<i>La Niña</i>) phases. This study investigates the effect of ENSO and local/regional abiotic factors on the interannual abundance (1996–2020) of the Plata pompano <i>Trachinotus marginatus</i>, a marine fish abundant along the southern Atlantic coast. Using monthly standardized data from the Brazilian Long-Term Ecological Research program (B-LTER), this study investigates the following: (1) long-term trends in the abundance of <i>T. marginatus</i> in the surf zone of a subtropical beach, and (2) the influence of local (temperature, water transparency, salinity), regional (rainfall, continental discharge) and climatic (ENSO phases) factors on this abundance. Through time series analysis and Generalized Additive Models with Bayesian adjustments, it was found significant interannual variation, with an overall decline. ENSO phases affect juvenile abundance, with <i>La Niña</i> having a positive impact and <i>El Niño</i> a negative one. Regionally, increased discharge from the large drainage basin of Patos Lagoon (~ 200,000 km²) correlates negatively with juvenile abundance in the marine surf zone adjacent to its estuary. Locally, factors such as salinity, temperature and water transparency positively influence abundance of juveniles. These findings show that abiotic factors acting at different spatial scales affect the abundance of the species, including climatic phenomena that are becoming more frequent and intense in the current global warming&#xa0;scenario.</p>