Review of the Bigscale Fish Family Melamphaidae (Beryciformes: Berycoidei) from Taiwan, with Comments on Morphology and an Annotated Checklist of the Beryciformes from Taiwan

The bigscale fish family Melamphaidae is a group of small deep-sea fishes found throughout most of the world's oceans. Scientists currently recognize 77 species, which inhabit waters ranging from the twilight zone (mesopelagic zone) to the deep ocean (bathypelagic zone), reaching depths down to 6,000 meters. Although these fishes rarely exceed 16 cm in length and have no commercial value, they are frequently caught as bycatch in deep-sea trawl fisheries and form an important part of deep-sea ecosystems.

Despite Taiwan's location adjacent to some of the deepest waters in the western Pacific, the diversity of Melamphaidae in Taiwanese waters has remained largely unknown. Prior to this study, only a single larval record had been reported, and no adult specimens had been formally documented. To address this knowledge gap, we examined museum collections and published records to review the species of Melamphaidae occurring around Taiwan. By documenting species diversity and updating distribution records, this study improves our understanding of Taiwan's deep-sea biodiversity and provides essential baseline information for future research, conservation, and marine resource management.

Research highlights

1. This study provides the first comprehensive review of the bigscale fish family Melamphaidae from Taiwanese waters, and identified four species belonging to three genera: Poromitra unicornis, Scopeloberyx robustus, Scopelogadus mizolepis, and Scopelogadus unispinis. In addition, a specimen of Scopelogadus was discovered but could not be confidently assigned to any known species because of its poor condition, suggesting that additional undocumented diversity may still exist.
2. This study also updated the checklist of Taiwanese beryciform fishes, recognizing 18 species from eight families and adding several new distribution records. These findings demonstrate that Taiwan’s deep-sea biodiversity is richer than previously recognized and highlight the important role of museum collections and taxonomic research in documenting marine biodiversity.

Social Impact

1. These fishes are important components of deep-sea ecosystems. Understanding what species occur in Taiwanese waters is the foundation for biodiversity conservation, environmental monitoring, and future ecological research. Without accurate species identification, it is difficult to assess ecosystem health, detect biodiversity loss, or evaluate the impacts of deep-sea fishing, mining, and climate change.
2. This research also highlights the importance of museum collections and deep-sea surveys. Many of the newly recorded species were discovered by reexamining specimens that had already been collected, demonstrating that valuable biodiversity information can remain hidden in collections for years.

Future works/solutions

1. Expanding deep-sea sampling around Taiwan, especially in poorly explored offshore regions.
2. Integrating DNA analyses with traditional morphology to identify cryptic or undescribed species.
3. Establishing long-term biodiversity monitoring programs to track changes in deep-sea ecosystems.
4. Increasing support for museum collections and taxonomic research, which provide the essential framework for all biodiversity studies.

Together, these efforts will improve our understanding of Taiwan’s deep-sea biodiversity and help inform future conservation and management strategies.

Melamphaid specimens collected from Taiwan. A. Poromitra unicornis. B. Scopeloberyx robustus. C. Scopelogadus mizolepis. D. Scopelogadus unispinis. E. Scopelogadus sp. Photos by Yu-Chieh Hsu (A, C, D)