Effect of freshwater discharge from Namgang Dam on ichthyoplankton assemblage structure in Jinju Bay, Korea

Abstract

The movement of fish eggs and larvae in bay and estuarine systems is affected by freshwater discharge. In this study, the assemblage structures of ichthyoplankton eggs and larvae were assessed for the first time in Jinju Bay, South Korea, to identify the spawning and nursery functions of the bay. Fish eggs and larvae and several environmental parameters were sampled monthly from April 2015 to March 2016 inside and outside of the bay. Within the bay we collected eggs and larvae from 25 and 35 species, respectively, indicating greater diversity than outside the bay, where we collected eggs and larvae of 20 and 28 species, respectively. Fluctuations in water temperature and salinity were larger inside than outside of the bay, and chlorophyll-a concentration was higher within the bay, likely due to discharge from the Namgang Dam, which causes water to flow from the inside to the outside of the bay. This process influences fish larva abundance, such that more larvae are found outside than inside the bay. We also found that 28 fish species use Jinju Bay as a spawning ground. For some species, the timing of egg and larva appearance differed inside and outside of the bay, suggesting that the timing of spawning may differ between the two environments.

Limited recovery following a massive seagrass decline in subarctic eastern Canada

“…Because numerous studies have shown a relationship between hydroelectric development and changes in water parameters (Friedl & Wüest, 2002; Myoung et al, 2021), we used trends in the mean freshwater discharge (m 3 s −1 ) per hydrological years (1 October to 30 September) as a proxy variable for potential changes over time in water parameters (e.g., salinity, nutrient concentrations, suspended particles in the water column) in nearshore environments of the eelgrass biomass monitoring sites. To investigate the influence of the LGR and local freshwater discharge on the temporal patterns of eelgrass density and aboveground biomass, we computed the freshwater discharge of three watersheds near eelgrass biomass monitoring stations and the La Grande River using the data of the ERA5 reanalysis model (Hersbach et al, 2020).…”

“…Because numerous studies have shown a relationship between hydroelectric development and changes in water parameters (Friedl & Wüest, 2002;Myoung et al, 2021), we used trends in the mean freshwater discharge (m 3 s −1 ) per hydrological years…”

Ichthyoplankton Assemblage Structure in Jinhae Bay, Korea

“…In Jinhae Bay, E. japonicus eggs were collected seven times, and 61,688 eggs/1000 m 3 (mean) accounted for 92.2% of the total, whereas 245 larvae/1000 m 3 (1.6% of the total) were collected five times. Many previous studies also collected more fish eggs than fish larvae: E. japonicus eggs and larvae, 52,885 eggs/1000 m 3 and 29,579 larvae/1000 m 3 from Jinju Bay (Myoung et al, 2021); 1,413 eggs/1000 m 3 and 174 larvae/1000 m 3 from northern Jinhae Bay (Han et al, 2018); and 1,455 eggs/1000 m 3 and 377 larvae/1000 m 3 from Yeongil Bay (Han et al, 2003). This phenomenon is due to the high density of fish eggs collected immediately after spawning; therefore, more individuals were collected near the spawning area.…”

“…Marine organisms struggle to adapt to the bay's diverse marine environment owing to its extreme variability (Faria, Morais, and Chícharo, 2006). Nevertheless, the bay plays an important role as a spawning and nursery area for various marine fishes (Myoung et al, 2021;Van Guelpen et al, 2021). The bay's marine environment is favorable for young fish to live; feed biomass is abundant owing to nutrients flowing from the land into the sea (Á lvarez et al, 2015;Newton et al, 2014).…”