• Journal of Aquaculture
• /
• v.14 no.1
• /
• pp.17-27
• /
• 2001

Effects of temperature (10, 12, 14, 16, 18 and 2$0^{\circ}C$) and salinity (22.0, 24.5, 27.0, 29.5, 32.0 and 34.5 ppt) were studied on incubation period, hatching success, survival and growth of alevin and juvenile seabass, L. japonicus. Embryonic development was accelerated with increasing temperature but it was not influenced by salinity. Hatching success was the highest at 14$^{\circ}C$ and 34.5 ppt. Higher temperature also accelerated the development of mouth opening, absorption of yolk and oil globules, and alevin growth. Survival of the 5-day old Juvenile was accelerated in the following order : 14<16<18<20<12$^{\circ}C$. Rearing experiment of the juvenile for 30-day indicated the faster growth at 13, 20 and 27 ppt than at 34 ppt.

• Journal of Animal Environmental Science
• /
• v.6 no.3
• /
• pp.141-151
• /
• 2000

Over-grown seaweeds in Donghae(east sea of Korea peninsula) may impedes ocean environment, however, they can be a good nutrient resources for poultry feeds if they are utilized properly. In this study, seaweeds powder were tested for laying hens\` ration to investigate the effects on egg production rate, egg quality and calcium phosphorus excretion. One hundred 65wks-old brown layers were fed for 5 weeks alotted with seaweeds powder addition to experimental diet by 0(control), 0.5, 1.0 and 2.0%, respectively, and obtained following results; 1. Seaweeds proved a mid-protein low-energy feed resources with planty of K, Na, Ca, Mg, Sr and Fe. 2. Seaweeds addition by 0.5% and 1.0% improved egg production rate and egg-mass output markedly(p<0.05) than control. Seaweeds addition did not alter cholesterol level of yolk and yolk index, however egg shell thickness showed increasing trend by increasing seaweeds addition level. 3. Protein absorption and digestibility in seaweed addition treatments were significantly higher(p<0.05) than control group and protein contents of excreta in 0.5% and 1.0% treatments were reduced(p<0.05), which suggests effective protein metabolism for egg production. Increasing seaweeds addition reduces Ca and P contents in rectum and excreta, suggesting Ca and P utilization improvement in laying hens and lessening soil pollution. 4. In conclusion, seaweeds addition in layers' diet by 1.0% level improves egg-mass production and might be egg quality by increasing metabolism of protein, calcium and phosphorus.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.50 no.3
• /
• pp.287-295
• /
• 2017

Egg development and morphological change of larvae of the Sakhalin sole Limanda sakhalinensis were studied by observing specimens obtained in a rearing experiment from fertilized eggs to the juvenile stage. The wild broodstock was collected in January 2010 and kept in a circular water tank (${\O}1.5{\times}1m$) at a temperature of $14.5{\pm}0.5^{\circ}C$. Fertilized eggs ranged from 0.72 to 0.82 mm ($0.77{\pm}0.07mm$, $mean{\pm}SD$) in diameter. The eggs were spherical, transparent and adhesive demersal. The egg yolk was divided from the oocyte 10 min after fertilization (AF), and an embryo was formed in 36 h AF. More than 50% of the eggs hatched within 133 h AF. The mouth and anus did not open until $3.5{\pm}0.25mm$ total length (TL). At 4, days after hatching (AH), the fish became larvae 3.7 to 4.2 mm ($4.0{\pm}0.36mm\;TL$), yolk absorption was completed and the mouth began to open. The left eye moved upward and the nostril moved to the right at 39 days AH. These post-larvae ranged from 8.0 to 9.9 mm TL ($8.9{\pm}1.33mm\;TL$). At 50 days AH, the fish became juveniles ($12.4{\pm}1.20mm\;TL$) There were 70-72 dorsal fin rays, 55-56 anal fin rays, 11 pectoral fin rays, and 6 ventral fin rays and the juveniles adopted a benthic life.

• Development and Reproduction
• /
• v.18 no.1
• /
• pp.33-41
• /
• 2014

We investigated the process of yolk absorption in Korean rose bitterling, Rhodeus uyekii, and determined the changes in its morphometric characteristics. The R. uyekii from 1 days post hatching (DPH) to 21 DPH, the eye diameter (ED) was 5.4 at 5 DPH. Thereafter, the ED/total length (TL) ratio increased to 10.7 at 21 DPH (p<0.05). The yolk length (YL) decreased from 95.4 to 1.1 by 21 DPH, and this rate of decrease was greater than that for any other dimension (p<0.05). 12 morphometric dimensions/TL for the R. uyekii were measured at each sampling day from 21 DPH to 170 DPH. At just hatching, the average TL and BW were $6.1{\pm}0.09mm$ and $4.9{\pm}0.07mg$, respectively. At 53 DPH, the average TL was $12.9{\pm}0.28mm$ and the average BW was $14.7{\pm}0.72mg$; the total length growth equation was $TL=5.507e^{0.038t}$ ($R^2=0.916$). Further, the body weight growth equation was $BW=3.3647e^{0.0296t}$ ($R^2=0.9354$). The dimensions with regard to body depth showed the greatest growth rates in the external characteristics of the fish (p<0.05). The patterns of the morphometric characteristics measured in this study can be classified in three ways. The patterns were shown to be increased (y=0.0992x+12.07, $R^2=0.8333$), decreased (y=-0.0569x+42.029, $R^2=0.8395$) or maintained (y=0.005x+18.263, $R^2=0.3678$) from 21 DPH to 170. These results will provide useful indices for the successful rearing of the R. uyekii.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.51 no.5
• /
• pp.549-555
• /
• 2018

The objectives of this study were to confirm the nutritional requirements and improve the survival of the walleye pollock Theragra chalcogramma, a cold seawater fish, by enrichment. We analyzed the fatty acids and amino acids of fertilized pollock eggs before hatching, just-hatched larvae, larvae that had absorbed only the yolk sac, and larvae starved for 2 days after yolk absorption. For the survival improvement experiment, we administered docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and DHA-EPA enrichment. Fatty acid decreased DHA and EPA content. On the $30^{th}$ day, body growth was significantly greater in pollock given the EPA and DHA-EPA treatments (P<0.05). Larval survival at 20 and 30 days after hatching (DAH) was greatest under the DHA-EPA treatment (P<0.05). Survival was significantly lower under the EPA treatment at 10 DAH, but then increased to approach that seen under the EPA-DHA treatment (P<0.05). Therefore, we determined that reduced survival in hatchlings of high-mortality pollack could be improved by controlling EPA and DHA content during enrichment. We conclude that cold seawater fish must be given feed that meets their nutritional needs, which can be accomplished using newly manufactured enrichment products for the larvae of cold seawater fish, such as pollock.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.1
• /
• pp.49-54
• /
• 2017

We collected and reared Theragra chalcogramma walleye pollock brood-stock for use in natural spawning tests and undertook to obtain domestic pollock via fertilized egg capture, development of fertilized eggs, and absorption of yolk sac after hatching. Whole pollock were caught with trammel and set nets and immediately placed in a deep-sea water tank. Adults were the most common pollock age group (43.0%; n = 86) among the 254 pollock captured in March 2014 with 57.9% (n = 147) being captured off Southern Gosung, Korea. The main spawning period of pollock is February (spawning phase of 91% of pollock). From the deep-sea tank, we collected 1640 mL of naturally fertilized eggs (~820,000 eggs) from 12 spawning events occurring between February 4 and 22 2015. The floating/ live eggs were maintained in deep-sea water tanks at $5.5{\pm}0.2^{\circ}C$. Egg size was $1.5{\pm}0.03mm$. Six hours after fertilization the eggs were at the 2 cell stage, and the eggs hatched approximately 340 hours after collection. At hatching, larval length and yolk sac area were $5.2{\pm}0.25mm$ and $9.5{\pm}1.00mm^2$ (100%), respectively. Four days after hatching, the yolk sac area was $2.2{\pm}0.53mm^2$ ($23.1{\pm}5.55%$). This is the first report of collection of naturally fertilized eggs from pollock and their subsequent hatching while held in an indoor deep-sea water tank. The results suggest that such collection could assist in the recovery of pollock resources and the possibility of domestic rearing of cultivated larvae.

• Asian-Australasian Journal of Animal Sciences
• /
• v.32 no.9
• /
• pp.1407-1413
• /
• 2019

Objective: This experiment aimed to investigate the effect of different sources and inclusion levels of dietary fat on productive performance and egg quality in laying hens raised under hot environmental conditions. Methods: A total of 480 Hy-Line Brown laying hens at 31 wk of age were randomly allotted to 1 of 5 experimental diets. The control diet contained 2,800 kcal/kg nitrogen-corrected apparent metabolizable energy with no fat addition. Four additional diets were prepared by adding 2.0% or 4.0% of animal fat (AF) or soybean oil (SO). Energy and nutrient concentrations were consistent among all diets. Diets were fed to hens for 4 weeks. Average daily room temperature and humidity were $26.7^{\circ}C{\pm}1.52^{\circ}C$ and $77.4%{\pm}4.50%$. The heat stress index was approximately 76, indicating that hens were raised under heat stress conditions. Results: Final body weight (BW) was greater (p<0.05) for hens fed diets containing 2.0% or 4.0% AF than for those fed the control diet or diets containing 2.0% or 4.0% SO. The BW gain and feed intake were greater (p<0.05) for hens fed diets containing additional AF or SO than those fed the control diet. Eggshell thickness was the greatest (p<0.05) for hens fed the control diet, but the least (p<0.05) for hens fed diets containing 4.0% SO. Egg yolk color was the greatest (p<0.05) for hens fed the control diet, but the least (p<0.05) for hens fed diets containing 4.0% SO. Conclusion: Inclusion of supplemental fat (AF and SO) in diets exhibits preventative effects on BW loss for hens raised under hot environmental conditions when energy and nutrient concentrations in diets were maintained. The effects were greater for AF than for SO. However, inclusion of supplemental fat in diets decreases eggshell thickness and egg yolk yellowness, possibly due to a reduction in Ca absorption and intake of egg yolk colorants.

• Fisheries and Aquatic Sciences
• /
• v.16 no.1
• /
• pp.25-34
• /
• 2013

Early ontogenic development in Siberian sturgeon Acipenser baerii was documented and the effects of different temperatures on embryonic and prelarval development were examined. Photograph-assisted data on morphogenesis in Siberian sturgeon prolarvae agreed well with published descriptions of their ontogeny and ecological behaviors, although certain aspects of differentiation, such as gill covering and scute development, could be rearing condition-sensitive. The present study provides the first characterization of the transient development of teeth during early larval stages; the pattern was congruent with the transition of prolarvae to exogenous feeding. From examinations of embryonic and prelarval development under different temperature conditions ($12-24^{\circ}C$), developmental speed was inversely related with temperature. Overall, hatchability was higher and hatching events were more synchronized at $20^{\circ}C$ than at lower temperatures. After hatching, similar patterns of temperature-dependency were observed in yolk sac absorption and the evacuation of the pigment plug. Our results suggest that the incubation of Siberian sturgeon embryos and prolarvae at temperatures close to $20^{\circ}C$ would be advantageous in hatcheries, based on reductions in the duration and uniformity of egg and prolarval developmental stages.

• Development and Reproduction
• /
• v.23 no.2
• /
• pp.171-181
• /
• 2019

To produce healthy and stable seed production, we need to obtain information and understand vision that affects behavior of red spotted grouper. We examined their expression and retinal development during the juvenile development. Short-wavelength sensitive opsin (SWS2), a cone photoreceptor, began to be expressed from lens and ear vesicle formation stage and its expression increased until 10 days after hatching (dah). In case of middle-wavelength sensitive opsin (MWS), its expression was detected at 3 dah and reached the highest level at 21 dah. The expression of long-wavelength sensitive opsin (LWS) was first observed from 3 dah and their expression decreased thereafter. Rhodopsin, a rod photoreceptor, was found to be expressed from 2 dah and its expression reached the highest level at 50 dah. The outer nuclear layer (ONL), inner nuclear layer (INL) and ganglion cell layer began to differentiate at 2 dah, while choroid first appeared at 4 dah so that the eyes became black. These results indicate that the development of retina mostly completes around 4 dah. It seems that the development of the retina and the expression of the opsin genes are closely related to the behavior such as hunting prey, considering that the timing of the completion of the development of the retina, the timing of gene expression, and the timing of completion of yolk absorption are similar.

• Korean Journal of Ichthyology
• /
• v.10 no.1
• /
• pp.1-10
• /
• 1998

The early history of Korean mandarin fish, Siniperca scherzeri was studied to obtain some information required in aquaculture and reinforcement of natural population. During the period from June 1996 to July 1997, the mature adults of Siniperca scherzeri were collected from the middle Soyang Lake at Puksan - myon, Chunchon - shi, Kangwon - do, Korea. The eggs from females were obtained by injecting HCG or/and GnRH - a and fertilized by dry method in the laboratory. The fertilized eggs, measuring 1.70~2.10 mm in diameter and expanded to 2.20~2.66mm after absorption of water, were globosity, light orange yellow, separative, submergence and had one large oil globules of 0.5~0.7 mm. The blastodisc was formed in 1 hour and cleavage started in 1 hour 30 min. after fertilization, and the intervals of each stage of cleavage was about 50 min. at the water temperature of $21{\sim}24^{\circ}C$. Hatching occurred 131 hours 30 min. after fertilization and newly hatched larvae were 5.86~6.85 mm in total length(TL) and numerous stellate melanophores were distributed on the yolk and abdomen of caudal peduncle. The yolk was almost absorbed and the teeth development. 3 days after hatching, at 6.98~7.60 mm TL. The head spines and the teeth were largely developed and all fins were completely formed and became postlarva stage 15 days after hatching, at 10.10~12.90 mm TL. The body shape and the color pattern were similar to adult, 25 days after hatching, at 15.3~23.8 mm TL. In 5 months after hatching were reached at 154.10~175.02 mm TL and 49.32~82.67 g in body weight.