Morphological properties of dark banded rockfish (Sebastes inermis) were analysed to investigate its acoustic scattering characteristics. Total of 18 live samples was prepared for X-ray photos and collected morphological coordinates of their body and swim bladder shapes. Kirchhoff-ray mode model was used to calculate acoustic scattering pattern for broad-band frequency range. Inclination of swim bladder ranged from 17 to 30 and the averaged value was about 25.2° (S.D.(standard deviation)=3.15). There were no any tendency of increase or decrease in volume and area ratio of swim bladder to fish body and ranged from 2.2 % to 4.43 % and 14.85 % to 21.31 %, respectively. The averaged value of volume and area ratio was 3.13 % (S.D.=0.52) and 17.6 % (S.D.=1.5). b20 values were –69.01 for 38 kHz, –69.83 for 70 kHz, –70.17 for 120 kHz and -70.93 for 200 kHz, recpectively. Broadband acoustic patterns of dark banded rockfish for 20 ~ 200 kHz were similar among samples and they reflected size and morphological properties of fish species.

The characteristics of aquatic light fields are generally reflected in the visual systems of fishes inhabiting them. Therefore, research on light sensitivity of fish is useful to explain the correlation between the visual function and habitat, behavior and distribution of fish. Rockfish is an important species in coastal ecology and also one of the main species for culturing in Korea. To make a contribution on the maintenance of the fish resources and understanding the ecology of the rockfish, the visual spectral sensitivities of the dark-adapted rockfishes were measured in the range of visible light (405~660 nm) using a light source of light-emitting diodes (LEDs). In order to assess electrophysiological response of the fish, the ERGs (electroretinograms) of the dark-adapted rockfishes were recorded on a data logger (12 bits) and a laptop computer. Juvenile (n=5; weight: 20.3±5.2 g; total length: 10.3±0.7 cm) and adult (n=5; weight: 87.8±21.8 g; total length: 18.1±1.3 cm) rockfishes were used in experiment. The visual threshold of juvenile and adult rockfish were 11.66 (log quanta/cm2/s) and 11.81 (log quanta/cm²/s) in 574 nm, respectively. The peak wavelength of the spectral sensitivity in the dark-adapted juvenile and adult rockfish was commonly 551 nm (series of green color). Collectively, these results demonstrate that the rockfish has suitable visual capabilities for inhabiting coastal water in Korea.

The aim of the present study was to assess the effects of ammonia on physiological responses in Korean rockfish (Sebastes schlegeli). Interestingly, no mortality were observed when the specimens (301.1±8.0 g) were exposed to five levels of un-ionized ammonia (NH3) (control, 1, 2, 4, 8 mg L-1) for 3 hours. Furthermore, a significantly higher increase in gill Na+/K+-ATPase (NKA) pump activity with was detected due to the ammonia exposure. The activity of the fishes were found to be 4 and 8 mg L-1 NH3, which was significantly high compared to normal 1 mg L-1 NH3. Although ammonia exposure had no effect on plasma Cl-, exposure to both 4 and 8 mg L-1 NH3, however it led to increase in the plasma Na+, K+ and osmolality levels. Also, prolong ammonia exposure cause increase of plasma cortisol and glucose levels. The increase in glucose was accompanied by an increase in cortisol. The fish exposed to 4 and 8 mg L-1 NH3 showed significantly higher hematocrit than control group than those exposed to 1 and 2 mg L-1 NH3. The intensity of cell damage increased with the increase concentration and exposure to ammonia. Furthermore, hyperplasia, separation and epithelial necrosis were also observed in gill tissues. Taken together, the results showed that direction of changes to the investigated parameters can be used to determine the physiological responses of Korean rockfish to ammonia.

This study is aimed to analyze the economic performance of black rockfish aquaculture by standardizing cost structures by region and farming size. The result of survey on farming and sale condition in each region, stocking density, survival rate, juvenile price, and unit production was the highest at Yeosu and Tongyeong, Heuksando showed the lowest. While rearing period was the longest at Tongyeong, the shortest region was Yeosu and Wando. In farming cost structure by region, amount of feeing was the highest at Tongyeong and Yeosu, and the lowest was Heuksando. Cost of medicine was high in Wando and Taean region, Yeosu and Hecksando was low. In case of farm size, feed cost ratio was high in the order of medium(0.75ha), small(0.25ha) and large(1.25ha) size. Standard production cost at every farm size of Heuksando showed the lowest among these regions. Taean and Yeosu was middle, and Tongyeong and Wando was the highest. According to the income, profit rate and investment return of farm size in all regions, as the bigger farm size, the higher income and profit rate was revealed. However, in case of Wando, Taean, and Heuksando which regions has high investment return, medium farm size was higher than large size. The result of economic analysis according to various factors, economic feasibility of black rockfish aquaculture in marine floating cage was showed significant changes by rearing and market condition.

Yellow clay dispersion has been applied to minimize fisheries impact by the red tide Cochlodinium polykrikoides blooms in Korean coasts since 1995. The present preliminary study documents the effect of yellow clay on Korean rockfish, Sebastes schlegelii, in terms of oxygen consumption rate (OCR). The OCR in the low clay suspension (0.05 and 0.23 %, w/w) showed normal level compared to the control. In contrast, the OCR for each one of three replicates in the high clay suspension (1.16 and 5.58 %, w/w) was not returned to the previous level that clay was not treated, indicating that high clay suspension (≥1.16%, w/w) might give negative effect on Korean rockfish. Overall, this result suggests that field application of clay to control Harmful Algal Blooms (HABs) may not give impact on Korean rockfish once the clay is dispersed in a low concentration (≤0.23%). In order to understand the changes of OCR in the repeated exposure to clay, it is required to do further studies on the changes of OCR when the fish is exposed to clay repeatedly after recovery in the normal seawater.

Characteristics of age and growth of the black rockfish, Sebastes inermis sampled in the Jeonnam Marine Ranching Area (JMRA) around Geumo Islands south of Yeosu were investigated using 642 otoliths from March 2009 to February 2010. The opaque zone was formed in September once a year and hence it was used as an annulus. The parturient period was December to January, and therefore the duration from fertilization to the complete formation of the opaque zone was nineteen months. From the parameters calculated using the average length when the year ring was formed, growth of S. inermis were expressed by von Bertalanffy growth equation as Lt=23.267 (1-e-0.4406(t+1.1971)) for females and Lt=22.030 (1-e-0.5312(t+0.6834)) for males when is total length in age t. Through the growth equations, the maximum length was determined as 23.27cm for females and 22.03cm for males and the growth factor as 0.4406/yr and 0.5312/yr, respectively. Finally, the growth of female S. inermis is larger than the one of male S. inermis.

E ffe ct of aluminum (al) on the plasma vite llogenin (VTG) , alkaline-labile phosphorus (ALP P ) , Calcium (Ca) , glutamate pyruvate transaminase (GP T) and hepatosomatic index (H SI ) we re examined in the e stradiol-17β (E 2)-administe red immature rockfish, Sebaste s schlege li. F ish we re intrape r itone ally inje cted with E 2 (5 ㎎/㎏ body we ight (B .W.) ) and/ or Al (0, 0.1, 1, 5 and 10 ㎎/㎏ B .W.) and then plasma we re extracted at 7 days. Thick VTG band was de te cted at a mole cularwe ight position of about 170 kD a in SD S-P AGE using the plasma of E 2-administe red rockfish. This band was reduced by the administration of Al to rockfish. Al reduced the concentrations of ALP P and Ca in a concentration-dependent way and a significant reduction occur red at Al concentrations gre ate r than 5 ㎎/㎏ and 10 ㎎/㎏, re spe ctive ly. The concentration of GP T was incre ased in concentration-dependent way at all the group of Al-administe red rockfish. H SI was reduced in a concentration-dependent way. The se re sults sugge st that Al inte r fe re with E 2-induced vite llogene sis by be ing toxic to hepatocyte .

n re cent ye ars, remarkable conce rn has be en eme rged ove r endocr ine disrupting chemicals (E D Cs) which mimic the e ffe cts of the ste roid hormone and modulate the endocr ine functions of human and wildlife . The biodegradation products of sur factants such as nonylphenol (N P ) have be en regarded as E D Cs. H oweve r , only few studie s have be en car r ied out to inve stigate the e ffe ct of E D Cs on vite llogene sis in mar ine fish. The pre sent study was unde r taken to the e ffe cts of 4-N P on the vite llogene sis of juvenile rockfish, Sebaste s schlege li. J uvenile rockfish we ighing about 50g we re intrape r itone ally inje cted with e stradiol-17β (E 2, 5㎎/㎏ body we ight) or 4-N P in 70% e thanol twice at 3-day inte rvals and blood sampling we re extracted from the fish at 7 days afte r the last inje ction. I ntense VTG bands we re de te cted at mole cular we ight position of about 170kD a in all the plasma of 4-N P -administrated fish as that of E 2-administe red fish. P lasma ALP P , Ca and GP T concentrations we re also incre ased in all the group of 4-N P -administe red fish. The addition of 4-N P to the we lls inhibited the binding activity E 2 to E R in a conve rse sigmoid fashion. The se re sults sugge sted that 4-N P induced VTG synthe sis by the binding affinity 4-N P to E R and acted on E D Cs in the juvenile rockfish