Seasonality and occurrence of the dominant mysid Neomysis awatschensis (Brandt, 1851) in the Yura River estuary, central Sea of Japan

Flexible herbivory of the euryhaline mysid <i>Neomysis awatschensis</i> in the microtidal Yura River estuary, central Japan

“…1). According to Omweri et al (2018), the five stations were divided into the lower estuary (R1 and R2 with river widths of 250-450 m and maximum depths of 4-7 m) and the upper estuary (R3-R5 with river widths of 70-120 m and maximum depths of 2-4 m). The lower and upper estuaries are characterized by regular and sporadic influences of seawater intrusions, respectively.…”

“…The population dynamics of N. awatschensis was recently reported from the microtidal Yura River estuary, which flows into Tango Bay, the Sea of Japan (Omweri et al 2018). The population exhibits a clear seasonality in abundance and reproduction in response to temperature.…”

“…The dominance of the genus Neomysis in estuaries can be attributed to its capabilities to withstand and adapt to highly changeable conditions, such as salinity (Pezzack & Corey 1979, Fockedey et al 2005 and temperature (Roast et al 1998a, Yamada et al 2007. In Japan, the euryhaline mysid Neomysis awatschensis (Brandt, 1851) including its junior synonym Neomysis intermedia (Czerniavsky, 1882) occurs widely in estuaries (Ikematsu 1963, Yamada et al 1994, Suzuki et al 2009, Omweri et al 2018) and lagoons (Murano 1963, Yamada et al 2007, Katayama et al 2011, Takahashi et al 2015. Despite its ubiquitous occurrence in various environments, the feeding habits of N. awatschensis have been reported only from Lake Kasumigaura (Nakamura et al 2020, references therein), where seawater intrusions have been blocked by slice gates since 1975.…”

“…To determine major food sources for N. awatschensis in the Yura River estuary, we analyzed specimens that had been collected along the estuary throughout the year (Omweri et al 2018). In contrast with sheltered and desalinated Lake Kasumigaura, the Yura River estuary was expected to impose large environmental fluctuations, such as river discharge and seawater intrusions (Kasai et al 2010, Watanabe et al 2014.…”

“…In contrast with sheltered and desalinated Lake Kasumigaura, the Yura River estuary was expected to impose large environmental fluctuations, such as river discharge and seawater intrusions (Kasai et al 2010, Watanabe et al 2014. To address spatiotemporal variations in physical conditions, the estuary was divided into the lower and upper estuaries and specimens were analyzed on a seasonal basis (Omweri et al 2018). Microscopy and stable isotope analysis were employed to gain direct evidence of ingested items and integrated information about assimilated food sources, respectively (cf.…”