• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.33 no.1
• /
• pp.55-59
• /
• 2000

A specific and sensitive sandwich enzyme-immunoassay (EIA) using Avidin-Biotin complex was developed for the measurement of GTH II levels in pituitary content and pituitary cell culture medium of the rainbow trout-(Oncorhpchus mykiss). Biotin-salmon GTH II rabbit IgG (sefondary antibody) wai purified by a protein A sepharose affinity chromatography column and that was biotinylated by using Biotin-N-hydroxysuccinimide ofter (BNHS). Non-biotin salmon GTH II rabbit IgG (first antibody) was obtained only through a protein A sepharose affinity chromatography column. The assay was performed by the so-called 'sandwich' method using a microtiter plate, A dose-response curve was obtained between $0.12 to 125 ng/ml$ of salmon GTH II. The displacement curves for pituitary extraction and pituitary cell culture medium of testosterone-treated rainbow trout were Parallel to the standard curie. The intra-assay and inter-assay coefficients of variation (CV) were $8.2{\%} (N=5) and 12.5{\%} (N=6)$, respectively, This assay system was used to measure the amount of GTH II that accumulated in the culture medium of dispersed pituitary cells in testosterone-treated immature rainbow trout, The accumulation was increased with the amount or salmon gonadotropin-releasing hormone. GTH II values determined by the present method were well correlated with those determined by radioimmunoassay. As a result, this assay system was found to be suitable for the measurement of GTH II for pituitary extraction and pituitary culture medium in many salmonid fishes.

• Korean Journal of Ichthyology
• /
• v.32 no.2
• /
• pp.103-109
• /
• 2020

The diet composition of whitespotted conger, Conger myriaster was studied using 129 specimens collected in the coastal waters Geoje, Korea from June 2018 to May 2019. The size of the specimens ranged from 11.5~22.9 cm in preanus length (AL). C. myriaster was a piscivore that consumes mainly pisces such as Engraulis japonicus and Gobiidae (%IRI: 98.4%). Of the fish species E. japonicus was the most preferred prey. Based on these results, it is considered that Conger myriaster has a characteristic of feeding on abundant prey organisms in the study area. The dietary compositions of C. myriaster was not significantly different among size classes. These results are considered to be due to a lack of specimens and the various size groups were not collected. Based on these results, it is thought that immature fishes inhabit the coast of Geoje. As body size of C. myriaster increased the mean weigh of prey per stomach (mW/ST) tended to increase (one-way ANOVA, P<0.05).

• Korean Journal of Ichthyology
• /
• v.11 no.2
• /
• pp.117-125
• /
• 1999

We investigated the reproductive cycles of two freshwater fishes, Moroco oxycephalus and M. lagowskii, in Korea. Seasonal changes in gonadosomatic index (GSI) and gonads were investigated histologically from April 1998 to April 1999. The reproductive cycles of two species were not shown any differences. The reproductive cycle can be divided into 5 phases : phase I (spent phase), phase II (immature phase), phase III (early developing phase), phase IV (late developing phase), and phase V (ripe phase). In phase I, the gonads of two species began to lose distinctly their weights from mid April, and reached the lowest GSI in late July (phase II). In September, the GSI values of testis and ovary increased very slowly (phase III) and gonadal developments rested during the winter season (phase IV). In March, the GSI values of M. oxycephalus and M. lagowskii began to increase, and reached the maximum in April (phase V). From the cyclic changes in the GSI and histological analyses, the spawning period was between mid April and mid May.