Abstract
Biological and physical surveys were conducted in order to investigate the relationship between environmental conditions and the distribution of ichthyoplankton and jellyfish, and dietary overlap between the ichthyoplankton and jellyfish in the Seto Inland Sea (SIS), Japan. Ichthyoplankton, copepods, and jellyfish were collected during two cruises in July 2005 in the Sea of Hiuchi and in July 2006 in Hiroshima Bay within the SIS. Sea surface temperature (˚C), salinity, bottom-layer dissolved oxygen (mg l -1 ) and the abundance (no. m -2 ) of fish eggs and larvae were significantly higher in the Sea of Hiuchi. Japanese anchovy was most dominant (69.3% in number of eggs and 52.3% in number of larvae) among the ichthyoplankton. Mean jellyfish biomass (g m -2 ) in Hiroshima Bay was significantly higher (50-folds) than that in the Sea of Hiuchi. Moon jellyfish was the most dominant among the jellyfish collected, accounting for 85.6% in wet weight. Surface temperature had a significant effect on fish egg and larval distribution: abundance of fish eggs and larvae increased with increasing temperature. Jellyfish abundance was negatively correlated with the bottom-layer oxygen concentration. Stable isotope analysis indicated dietary overlap between the Japanese anchovy and the moon jellyfish in Hiroshima Bay.
Highlights
An increase in the abundance and biomass of large gelatinous zooplankton such as cnidarians and ctenophores has occurred in marine ecosystems around the world (Purcell and Arai, 2001; Brodeur et al, 2002), potentially causing a significant impact on smaller zooplankton and their predators in pelagic ecosystems (Uye and Ueta, 2004; Haslob et al, 2007)
SUMMARY: Biological and physical surveys were conducted in order to investigate the relationship between environmental conditions and the distribution of ichthyoplankton and jellyfish, and dietary overlap between the ichthyoplankton and jellyfish in the Seto Inland Sea (SIS), Japan
Ichthyoplankton, copepods, and jellyfish were collected during two cruises in July 2005 in the Sea of Hiuchi and in July 2006 in Hiroshima Bay within the SIS
Summary
An increase in the abundance and biomass of large gelatinous zooplankton such as cnidarians and ctenophores has occurred in marine ecosystems around the world (Purcell and Arai, 2001; Brodeur et al, 2002), potentially causing a significant impact on smaller zooplankton and their predators in pelagic ecosystems (Uye and Ueta, 2004; Haslob et al, 2007). Recent laboratory experiments reported that bell contraction rate and predation rate on fish larvae by moon jellyfish under oxygen concentrations of
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