We investigated the seasonal occurrence and vertical distribution/migration of larval and juvenile northern smoothtongue, Leuroglossus schmidti (Pisces, Bathylagidae), in oceanic areas of the western subarctic Pacific. This species was the most abundant larval fish and one of the most abundant juvenile/adult fish at the study site. Larval recruitment of this species occurred in early March to mid-October. Larvae were found, however, throughout all seasons, suggesting that some had overwintered. The highest abundance (5.8 individuals m–2) of larvae was in summer. During summer and autumn, hatching mainly occurred at 100–150-m depth and larvae migrated toward the surface with growth. Once larvae reached about 20 mm in length, they moved below 100 m, and larger larvae (over 24 mm) exhibited diel vertical migration. The abundance of juveniles integrated through the water column was relatively constant (0.3 individuals m–2) throughout the study period. They were collected from below 300 m during the day, and part of the population (13–38%) swam into the epipelagic layer at night. The information on early stages of L. schmidti presented here provides a basis for future investigations of mesopelagic fish ecology in oceanic areas of the western subarctic North Pacific Ocean.

中文翻译：

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亚北极西太平洋北部光滑舌Leuroglossus schmidti (Pisces, Bathylagidae)幼体和幼体的季节性发生和垂直分布

我们调查了幼体和幼体北方平滑舌的季节性发生和垂直分布/迁移，鳐鱼（双鱼座，Bathylagidae），在西亚北极太平洋的海洋区域。该物种是研究地点最丰富的幼鱼和最丰富的幼鱼/成鱼之一。该物种的幼虫招募发生在 3 月初至 10 月中旬。然而，在所有季节都发现了幼虫，这表明其中一些已经越冬。最高丰度（5.8 个体 m–2) 的幼虫是在夏天。夏秋两季，孵化主要发生在100～150米深度，幼虫随生长向地表迁移。一旦幼虫长度达到约 20 mm，它们就会移动到 100 m 以下，而较大的幼虫（超过 24 mm）则表现出垂直迁移。通过水柱整合的幼体丰度相对恒定（0.3 个体 m–2) 在整个研究期间。它们白天从 300 m 以下收集，部分种群（13-38%）在夜间游入上层海层。早期阶段的信息L. schmidti这里介绍的为未来研究亚北极西部北太平洋海洋区域的中层鱼类生态学提供了基础。