Changes in the food selectivity of zooplanktivorous fishes related to the effects of nutrient enrichment in an urban tropical estuary.

Juvenile fish use estuarine ecosystems due to appropriate refuges and food supply found in these environments. The objective of this study was to investigate whether variations in the diet composition of juvenile fishes were mediated by changes in the availability of zooplankton prey in an urban estuary. Changes in fish foraging and prey selectivity were affected by nutrient enrichment. Calanoida and Cyclopoida were the most abundant items present in all zones and seasons, and for this reason, these were the items that most contributed to the fish diet. Shift in feeding strategy associated with eutrophication was registered due to a decrease in water quality. All species showed some contamination with microplastic particles and exhibited selectivity over them. The use of food resources available for fish is likely to be representative of estuarine habitat quality and may provide valuable information on the ecological status of estuaries.