Distribution expansion of a tropical fish species Elops smithi (Elopiformes: Elopidae) in the southwestern Atlantic Ocean.

Understanding the response of the organisms to climate alterations is one of the central goals of biology and ecology studies.Particularly, ocean warming has profound consequences for the ecosystems globally.Body size, diet shifts, and geographical range distributions alterations (e.g.ocean tropicalization), are the most frequent reported responses.Particularly, the southern portion of the SWA is considered a hotspot of ocean warming and the presence of several tropical species has been reported from this region.In this work we studied the southward range expansion of a tropical fish species Elops smithi, which inhabits the western Atlantic Ocean.The species is frequently captured in the tropical and subtropical coast of the southwestern Atlantic Ocean (SWA), where it lives in sympatry with E. saurus in part of their distribution.Elops smithi is distributed in the north of South America and the whole Caribbean Sea, while E. saurus has a northern distribution, in the eastern coast of North America and Gulf of Mxico.We studied the distribution expansion of E. smithi in the SWA using data from literature (from 1988 to 2019) and data collected between 2008-2022.We observed an increased frequency of the reports of E. smithi at latitudes higher than 33S from it first record in 2008.We found specimens in a wide range of sizes, from leptocephalus larvae to adults (48 cm in standard length).Specimens were captured in a wide range of environmental conditions, sea surface temperature (11.5-26.8C) and salinity (1.5-32 psu), along 350 km of the Uruguayan coast.This suggests that the presence of the species is much more common than only sporadic occurrence associated with specific thermal anomalies.Additionally, we suggest revising the identification of records from E. saurus in the SWA, which probably belong to E. smithi, which only differ by vertebrae counts.We highlight the need to study the potential interactions of the arrived species with the native fauna, which is considered as an important consequence of climate change.