Length–weight relations for 14 fish species (Actinoptergii) from the coastal waters off Gwangyang Bay, South Korea

Length–weight relations were estimated for 14 fish species sampled from the coastal waters off the Gwangyang Bay in South Korea. The following species were studied: Okamejei kenojei (Müller et Henle, 1841); Muraenesox cinereus (Forsskål, 1775); Thryssa adelae (Rutter, 1897); Thryssa kammalensis (Bleeker, 1849); Tribolodon hakonensis (Günther, 1877); Inimicus japonicus (Cuvier, 1829); Chelidonichthys spinosus (McClelland, 1844); Jaydia lineata (Temminck et Schlegel, 1842); Sillago japonica Temminck et Schlegel, 1843; Pholis nebulosa (Temminck et Schlegel, 1845); Favonigobius gymnauchen (Bleeker, 1860); Pampus echinogaster (Basilewsky, 1855); Cynoglossus joyneri Günther, 1878; Takifugu niphobles (Jordan et Snyder, 1901).The length–weight relation of Thryssa adelae (Rutter, 1897), (Engraulidae) has not been previously reported. The new maximum total length of Thryssa kammalensis (18.0 cm) is now provided. The values of coefficient a ranged from 0.0007 to 0.0218, and the values of exponent b ranged from 2.82 to 3.52.

Parallel adaptations of Japanese whiting, Sillago japonica under temperature stress

Knowledge about the genetic adaptations of various organisms to heterogeneous environments in the Northwestern Pacific remains poorly understood. The mechanism by which organisms adapt to temperature in response to climate change must be determined. We sequenced the whole genomes of Sillago japonica individuals collected from different latitudinal locations along the coastal waters of China and Japan to detect the possible thermal adaptations. A total of 5.48 million single nucleotide polymorphisms (SNPs) from five populations revealed a complete genetic break between the China and Japan groups. This genetic structure was partly attributed to geographic distance and local adaptation. Although parallel evolution within species is comparatively rare at the DNA level, the shared natural selection genes between two isolated populations (Zhoushan and Ise Bay/Tokyo Bay) indicated possible parallel evolution at the genetic level induced by temperature. Our result proved that the process of temperature selection on isolated populations is repeatable. Additionally, the candidate genes were functionally related to membrane fluidity in cold environments and the cytoskeleton in high-temperature environments. These results advance our understanding of the genetic mechanisms underlying the rapid adaptations of fish species. Projections of species distribution models suggested that China and Japan groups may have different responses to future climate changes: the former could expand, whereas the latter may contract. The results of the present population genomic work expand our understanding of genetic differentiation and adaptation to changing environments.

Dietary Value of Waste-Fed Rotifer Brachionus rotundiformis on the Larval Rearing of Japanese Whiting Sillago japonica

Live food resources are useful for larval fish rearing. However, production of sufficient live food resources is expensive. This study employed a cost-effective rotifer culture technique using fish waste diet (FWD) and investigate the effect of the FWD-fed rotifer on larval rearing of the Japanese whiting, Sillago japonica. Fertilized eggs of S. japonica were hatched in polycarbonate tanks containing 100 l of artificial seawater at 10 eggs l-1 with 50 ml min-1 of aeration at room temperature. Two diets (i.e. FWD-fed rotifers and rotifers fed with super fresh Chlorella-V12 as control) were used with 10 rotifers ml-1 for 10 days. Fish were sampled every two days for morphometric and gut content analysis. Fatty acid analysis was done for both rotifers and fish larvae. The fish larvae fed with FWD-rotifers had higher total length than those given control diet. There was no significant difference in survival rate, viability, dry weight, gut content, head length, eye diameter, and body depth between the two diets. The DHA recorded of total lipid for the fish given FWD-rotifer and control fish are3 5.2% and 18.2% respectively. The use of waste-fed rotifers is cost-effective method to enhance the production of larval fish rearing in hatcheries.