Trophic ecology of a highly abundant pelagic fish (Trachurus lathami) in a coastal marine ecosystem (39º - 42º S; Southwest Atlantic) related to environmental variability

Abstract

This study aimed to assess the feeding habits of rough scad T. lathami, an important pelagic fish in a Southwest Atlantic coastal marine ecosystem (El Rincón, 39º-42º S), during early (ES) and late (LS) spring of 2019. Trophic incidence (TI), relative importance (% RI) of prey items in stomach contents (n = 279), feeding strategy, ontogenetic shift in diet (multiple hypothesis modelling), and the relationship of diet with zooplankton abundance and with oceanographic conditions (multivariate analyses) were determined. Trophic incidence varied between ES (49 %) and LS (77 %), with a greater diversity of prey in the environment and the stomachs during the latter. Planktonic crustaceans prevailed, with copepods as the dominant prey in both spring periods (ES: RI 99 %; LS: RI 86 %). Large copepods (> 1 mm) dominated in ES, whereas small copepods (< 1 mm) dominated in LS. Amphipods, pteropods, bivalve larvae, decapod larvae, mysidaceans and bony fish remains were rare prey (% RI < 10). Feeding strategy analysis suggested a specialization at a population level on copepods (filter-feeding) and the occasional ingestion of other prey (active predation). A moderate correlation was observed between the diet and bottom temperature, thus suggesting their potential influence on rough scad feeding habits. Results highlight the opportunistic behaviour of rough scad in matching its diet to the most abundant prey in the environment, reflecting its plasticity in adapting to their short-time variations.