KOREASCHOLAR

Rapid morphological changes in fish larvae during growth make adult classification criteria ineffective for identifying larval fishes. Therefore, species identification of fish larvae requires understanding morphological changes during growth stages within and between species. However, for many fish larvae, the lack of morphological trait information, along with physical damage or protein degradation that occurs during specimen collection and preservation in the wild, creates obstacles for morphology-based identification. A fish larva (10.0 mm SL) collected from the coastal waters of the western Korean Peninsula in August 2019 exhibited morphological characteristics and melanophore distribution patterns closely matching those of an unidentified species of the family Platycephalidae (sp.5). Its MT-CO1 amplicon sequences identified it as Cociella crocodilus, through genetic similarity with MT-CO1 reference sequences and phylogenetic analyses of related species. This study provides significant insights into the early life stages of Cociella crocodilus, marking the first identification of this species at the larval stage.

Abstract
1. INTRODUCTION
2. MATERIALS AND METHODS
    2.1. Sample collection and initial processing
    2.2. Morphological observation andmeasurements
    2.3. Genomic DNA extraction andlibrary preparation
    2.4. Amplicon sequencing and ASV analysis
    2.5. Construction of the MT-CO1 referencelibrary
    2.6. Validation using fish-specific primersand MinION MK1C sequencing
    2.7. Phylogenetic analysis andspecies identification
3. RESULTS AND DISCUSSION
CRediT authorship contribution statement
Declaration of Competing Interest
ACKNOWLEDGEMENTS
REFERENCES

• Sihyun Park(Ocean Science, KIOST School, University of Science and Technology, Daejeon 34113, Republic of Korea, Ocean Climate Response & Ecosystem Research Department, Korea Institute of Ocean Science & Technology, Busan 49111, Republic of Korea)
• Sung Kim(Ocean Science, KIOST School, University of Science and Technology, Daejeon 34113, Republic of Korea, Ocean Climate Response & Ecosystem Research Department, Korea Institute of Ocean Science & Technology, Busan 49111, Republic of Korea) Corresponding author
• Hae-Young Choi(South Sea Fisheries Research Institute, National Institute of Fisheries Science, Yeosu 59780, Republic of Korea)
• Byung-Sun Chin(Department of Marine Biotechnology, Anyang University, Incheon 23038, Republic of Korea)
• Han-Sam Lee(Department of Marine Biotechnology, Anyang University, Incheon 23038, Republic of Korea)