New distribution record of Megalops atlanticus Valenciennes , 1847 ( Elopiformes , Megalopidae ) in El Salvador , Eastern Pacific Ocean

A new geographical distribution record of an Atlantic Ocean species, Megalops atlanticus Valenciennes, 1847, is reported on the Tropical Eastern Pacific Ocean based on 2 incidental captures by local fishermen at the Acajutla city, El Salvador. Two photographs, which give clear evidence of this species, demonstrate the increasing range of M. atlanticus in the Tropical Eastern Pacific. Regional monitoring of this species occurrence is recommended.


Introduction
The Atlantic tarpon, Megalops atlanticus Valenciennes, 1847 (sábalo real or tarpon in Spanish) is distributed on both sides of Atlantic Ocean.Along the western Atlantic, it occurs from Virginia (USA) to Brazil (Matamoros et al. 2009, Vega-Rodríguez and Ayala-Pérez 2014, Robertson and Van Tassell 2015, Garrone-Neto and Rodrigues 2018), and occurs in marine, estuarine, and continental ecosystems (Robertson and Van Tassell 2015).Recently, this species has also been recorded along the coastline of several countries in the Tropical Eastern Pacific (TEP), including Colombia, Panama, and possibly Costa Rica (Robertson and Allen 2015).The International Union for Conservation of Nature classifies this species as Vulnerable due to habitat degradation and fisheries in the Atlantic Ocean, but on the contrary, no category has been established for this fish in the TEP.Moreover it is not included in any CITES appendices.
Megalops atlanticus presents some important fisheries along the Pacific coast of Colombia (Neira and Acero 2016), but there are no scientific records of economic use of this species in neighboring countries.In the Atlantic this species has an important recreational fishery.
I present the first records of M. atlanticus in El Salvador, reflecting the dispersion of this species in the TEP.

Methods
The new records presented are based on 2 incidental and confirmed captures of M. atlanticus by recreational fishermen at Acajutla pier on the west coast of El Salvador.I used the description by Robertson and Van Tassell (2015) to identify the fishes in the photographs, and R. Robertson confirmed these identifications (pers. comm., 4 September 2017).
The fishermen used live mullet (Mugil spp.) and ate the fishes in both cases; therefore, the only evidence is the reports and the images of both specimens, as presented here (Figs 2, 3).Capture of second specimen was shared on social media (https://www.facebook.com/profile.php?id=100011424489095).The survey of fishermen found no other reports of this species from along the coast of El Salvador.
Identification.Specimens on photographs displayed the typical compressed and elongated body, silvery body, large scales, oblique mouth that opens upwards, and a projecting low jaw; moreover, there are no similar looking species in the TEP (Robertson and Allen 2015).Based on the photographs, the specimens measured 0.9 m and 1.0 m long (first and second specimen, respectively), and the fisherman of the second specimen stated that the fish weighed 9.1 kg.

Discussion
The new records based on 2 incidental captures of M. atlanticus at Acajutla Municipality provide evidence that this species is spreading northward in the TEP.The closest previous record of M. atlanticus is at Coiba Island, Panama (07°38ʹ54ʺ N, 081°44ʹ51ʺ W) (OBIS 2018), which is about 1100 km from Acajutla Pier.In the 1930s this species was already on the Pacific side of Panama Canal (Hilldebrand 1939); it had crossed from the Atlantic regardless of physical and salinity barriers.Later, McCosker and Dawson (1975) reported M. atlanticus at the upper east chamber of Miraflores lock (near the Pacific Ocean), and most recently, Robertson and Allen (2015) considered that this species crossed the Isthmus of Panama by way of the Panama Canal and now occurs in some parts of the TEP.Although this species crossed into All records of this species within the TEP are from within the Panamic province, which encompasses coastal waters from Mexico to southern Ecuador (Robertson and Cramer 2009).The southernmost TEP occurrences of this species are in the gulfs of Cupica and Tribugá, Colombia, where Neira and Acero (2016) documented artisanal fisheries on this species.
My survey of fishermen from different areas of the coast of El Salvador found no additional observations for this species.Regional monitoring on the geographical distribution is needed to document possible environmental impacts such as predation, although there are no declines of other fish species due to the presence of M. atlanticus in the TEP (Castellanos-Galindo and Zapata-Padilla 2013, Robertson andAllen 2015, Neira andAcero 2016).Research is required to determine causes of the recent dispersal of M. atlanticus in the TEP.