Bregmaceros Tompson, 1840

Genus Bregmaceros Tompson, 1840 View in CoL

Remarks Bregmaceros otoliths are relatively common in the collection, although many of them are represented by juveniles and/or poorly preserved specimens. Te taxonomy of extant Bregmaceros species in the region has been subject to ongoing revision (Ho et al., 2011; Koeda & Ho, 2019), with new species still being named (Ho et al., 2020). It has been suggested that Bregmaceros mcclellandi Tompson, 1840 may not exist outside of the northern Indian Ocean (Froese & Pauly, 2023) and that previous records of B. mcclellandi in Taiwan is a misidentified species of Bregmaceros pseudolanceolatus Torii, Javonillo & Ozawa, 2004 (Ho et al., 2011). Consequently, the identification of corresponding Bregmaceros otoliths also requires updating. For example, the otoliths of B. mcclellandi in Lin and Chang (2012) contain misidentifications, and those in Rivaton and Bourret (1999) may represent a mixture of several Bregmaceros species. Images of extant Bregmaceros otoliths from Taiwan are provided in Fig. 12 View Fig for comparative purposes.

In the present collection, otoliths of Bregmaceros japonicus Tanaka, 1908 and Bregmaceros nectabanus Whitley, 1941 are recorded (see below). Both species are characterized by a robust and wide dorsal lobe, distinguishing them from other Bregmaceros species in the region that possess a narrower dorsal lobe or a pointed, antenna-like dorsal denticle ( Fig. 12d–g, j–k View Fig ). Te distinction between B. japonicus and B. nectabanus is subtle, but B. japonicus typically exhibits a broader and more extended posterior lobe positioned just behind the caudal depression, resulting in a stockier otolith outline. In contrast, B. nectabanus displays a less pronounced posterior lobe located above the caudal depression, giving the otolith a slender outline that inclines towards the anterior.