Seasonal and ontogenetic change in diet composition of wild new world silverside Odontesthes argentinensis in temperate coastal area (South America)

Abstract

The Southwestern Atlantic coast (32–38°S) is one of the regions most affected by environmental changes (temperature, salinity, etc.), which can influence all life stages of fish species like de ones belong to the family Atherinopsidae (neotropical silversides). Considering that silverside species adapt easily to changing environments, we studied the diet composition and feeding strategy in relation with seasonal changes (intra- and inter-annual) and ontogenetic development of the silverside Odontesthes argentinensis. Stomach content of 416 specimens sampled between October 2015 and March 2017 (Partido de La Costa) and 68 specimens between July 2017 and August 2018 (Samborombón Bay) were analyzed. Zooplankton samples were taken and seawater environmental parameters were measured. The relative contribution of each prey was calculated and their evaluation by Amundsen graphical method, determined that importance of each prey, feeding strategy and niche width of O. argentinensis, changed not only among development stage but also among season and years. Results suggested that these variations were a reply to the complex environmental variation which affected the availability of food, so O. argentinensis could be used as regional indicator of environmental variations. The information obtained in this study evidences the importance of knowing variations in feeding strategy to get a better growth rate during rearing in captivity.