Species composition, distribution, and growth of Diaphus “slender-type” larvae (Pisces: Myctophidae) in the Kuroshio waters of the East China Sea

Chiyuki Sassa, Motomitsu Takahashi, and Youichi Tsukamoto

Larvae of the myctophid Diaphus “slender-type” form a dominant component of the late winter larval-fish assemblage in the Kuroshio waters of the East China Sea. However, ecological information on the larvae at the species level is limited due to difficulties with morphological identification. Based on species identification using mitochondrial DNA analysis, we describe the species composition, distribution, and growth of Diaphus “slender-type” larvae. Larvae of 6 species were found. Diaphus fulgens was the most abundant, accounting for 75.5% of the total catch, followed by D. kuroshio (14.0%) and D. slender sp. 1 (8.5%). Diaphus fulgens occurred over a broad area in the Kuroshio waters. Diaphus kuroshio occurred abundantly in the northeastern part of the study area, while the other 4 species were more abundant in the southwestern part. There was no significant interspecific difference in both mean absolute growth rates (AGR) and the weight-specific instantaneous growth coefficients (Gw) of D. fulgens, D. kuroshio, and Diaphus slender sp. 1 (0.105–0.119 mm/d and 0.094–0.118 d1, respectively). The AGR of the larvae of the 3 species were markedly lower than previously reported values for other genera of myctophids in subtropical waters, while the Gw were within the range of the other myctophids.

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