Journal Article Distributions of larval and juvenile/adult stages of the Antarctic myctophid fish, Electrona antarctica , off Wilkes Land in East Antarctica

12pp.99 - 108 , 2017-06
Myctophid fish are an important component of the Southern Ocean food web because of their very high biomass. This study investigated the spatial distributions of larval and juvenile/adult stages of the Antarctic myctophid Electrona antarctica. Fish were sampled in January 2011 and 2012 on a transect along 140°E and in January 2013 along 110°E using two different opening/closing net systems. In total, 1075 specimens of E. antarctica were collected: 948 larvae, 127 juveniles/adults, and 2 in the transformation stage. Most larvae were collected at 5–200 m depth, with diel vertical migration (DVM) not apparent. Larvae were mainly distributed in the Modified Circumpolar Deep Water (−1.5 °C–2.0 °C). By contrast, an analysis of the echogram at 38 kHz and discrete depth samples implied that juveniles/adults undertook DVM except in the continental slope area (65.5°S). As the distribution of krill is limited to the cold water mass (<–1.5 °C) along the continental slope, E. antarctica and krill populations are spatially separated off Wilkes Land during summer. According to the previously estimated larval period of 30–47 days, E. antarctica may spawn in late November to December in the marginal ice zone or near the sea ice edge. This study suggests that the environment related to sea ice provides a nursery ground for early stage larvae of E. antarctica.
本研究は、南大洋生態系において重要なハダカイワシ科魚類Electrona antarctica仔魚と稚魚/成魚の空間分布を明らかにした。仔魚のほとんどは深度5-200 mのModified Circumpolar Deep Water (−1.5 °C–2.0°C) に分布しており、日周鉛直移動は観察されなかった。一方、エコーサウンダー(38 kHz)と層別採集のデータから、最も南側の大陸棚斜面の観測点を除いて、稚魚以降の発育段階では日周鉛直移動を行っていることが分かった。夏季のウィルクスランド沖では、ナンキョクオキアミが主に大陸棚斜面の–1.5 °C以下の水塊に分布していることから、E. antarctica仔魚とオキアミの分布が空間的に分かれていることが明らかとなった。既往の知見と合わせると、産卵期は11月下旬から12月の海氷縁辺域と推定され、海氷近傍の環境が初期仔魚の育成場となっていることが示唆された。

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