Anguillid leptocephali of three Congridae species (Conger conger, Ariosoma balearicum and Gnathophis mistax) were caught as bycatch of pelagic trawls during acoustic surveys targeting small pelagic fish species in the southern Adriatic Sea, carried out under the framework of the Italian MEDIAS project (western side) and its extension in the ambit of the FAO AdriaMed project (eastern side). Results refer to the findings of Congridae leptocephali during surveys conducted in 2011, 2014, 2015 and 2016. A total of 25 specimens were caught and analysed (morphological features and pigmentation patterns). Leptocephali of Conger conger were found in the range of 8.4–13.1 cm total length (TL) (between 50 and 132 m depth), Ariosoma balearicum from 9.7–12.2 cm TL (between 50 and 128 m depth) and for Gnathophis mystax in the range from 6.4–11.7 cm TL (between 40 and 79 m depth). The results indicate that the southern Adriatic Pit could be the spawning area of these species in the Adriatic Sea. Present data represent a contribution to existing knowledge about the ecology of leptocephali from the Congridae family in the southern Adriatic Sea, and also indicate the existence of differences in morphometric parameters between different areas, that is, the possibility of the existence of new geographic lines within the genus Ariosoma in the Adriatic Sea.

A large often greenish-appearing type of leptocephalus larva has been observed and photographed or filmed by divers at 4 different locations within the Indonesian Archipelago from 2008 to 2011, and this paper documents these sightings and evaluates what can be learned about this type of unusual eel larvae. These leptocephali (~300–400 mm long) appear to be exceptionally large metamorphosing larvae of some type of moray eel of the family Muraenidae. Because of the morphological similarities between these larvae and ribbon eels, Rhinomuraena quaesita, they are hypothesized to be their larvae, which have never been distinguished among leptocephali of the Muraenidae. These leptocephali were observed at Sangeang Island, in Lembeh Strait adjacent to north-eastern Sulawesi Island, in two different years at Ambon Island, and on two consecutive days at Bali, between December and June of 4 different years. All observations of the large leptocephali were at depths shallower than about 23 m in areas with mixed coral rubble or coarse sand and silt substrates during daylight hours. The larvae used various styles of anguilliform swimming and swam near the bottom or in the lower water column while being observed. One larva tried unsuccessfully several times to enter small crevices. They were all at the metamorphosing stage and may have been entering coastal habitats to find a hiding place where they could transform into juvenile eels. Further studies are needed to clearly identify these large leptocephali and to learn about their life history.

Two notacanthiform Tiluropsis type leptocephali are analysed, thus constituting the southernmost report in the Atlantic Ocean. Specimens are compared with others of the kind taken from the literature. Some considerations about their larvae and Halosauridae, the family they would belong to, are supplied.