• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.1
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• pp.1-8
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• 1996

The effects of temperature and salinity on hatching rate of fertilized egg were examined to develop the method for the efficient seed production in fleshy shrimp, Penaeus chinensis. At the temperature ranging from $20^{\circ}C\;to\;24^{\circ}C$, the hatching rate increased with temperature and the highest hatching rate $(95.5\%)$ occurred at $24^{\circ}C$. But, with the temperature above $26^{\circ}C$, the hatching rate decreased suddenly, and at $30^{\circ}C$, the egg did not hatch at all. The hatching rate increased with salinity within the range of $20\%_{\circ}\;to\;31\%_{\circ}$ and the highest hatching rate $(95.5\%)$ occurred at $31\%_{\circ}$. However, with the salinity above $31\%_{\circ}$, the rate decreased abruptly, and it was only $25.5\%\;at\;40\%_{\circ}$. The hatching speed of egg was the fastest at $24^{\circ}C$. The hatching rate at $24^{\circ}C$ with the salinity of $31\%_{\circ}\;was\;30.5\%$ within 18hrs of the hatching experiment and it attained to $95.5\%$ within 48hrs of the hatching experiment. At $24^{\circ}C$, the hatching rate with the salinity of $30\~31\%_{\circ}$ is 1,2 times higher than that of egg with the salinity of $33\~35\%_{\circ}$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.6
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• pp.665-670
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• 2011

The rotifer Brachionus plicatilis is one of the most important food organisms in aquaculture. The resting eggs produced by mictic female rotifers are easily stored and hatched, making them useful as the starter for the mass culture of rotifers in marine larval culture. This study examined the optimum preservation method for resting eggs to ensure a high hatching rate. To produce resting eggs, the marine rotifer B. plicatilis was cultured with Nannochloris oculata (KMMCC 16). The resting eggs were harvested and cryopreserved using 5% and 10% methanol (MeOH), dimethylsulfoxide (DMSO), and glycerol as cryoprotectant agents (CPAs). The cryopreservation comprised slow or rapid freezing and the resting eggs were stored for one month in liquid nitrogen ($-196^{\circ}C$). The resting eggs were also dried at different temperatures (30, 40, and $50^{\circ}C$) and for different times (1, 2, and 3 h). In general, the hatching rates of the resting eggs preserved with CPA were higher than those without CPA and the slow freezing method was better than the rapid freezing method. However, the optimum CPA concentration for the hatching rate of the resting eggs varied with the freezing method and kind of CPA, and the CPA also affected the viability of the resting eggs. Dried resting eggs had a high, rapid hatching rate over 80%. The moisture content of the resting eggs cryopreserved in liquid nitrogen affected the hatching rate. Drying at $30^{\circ}C$ for 1 hour resulted in a high hatching rate of the resting eggs. In conclusion, drying at $30^{\circ}C$ for 1 hour and preservation in liquid nitrogen with the slow freezing method, without CPA, is recommended for a high hatching rate (ca. 95%) of rotifer resting eggs.

• Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.417-420
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• 2011

In this experiment, we examined the survival, fertilization, hatching times, and hatching rates of Far Eastern catfish Silurus asotus at pH ranging from 2 to 13 under laboratory conditions. Eggs could be fertilized at pH 3-12. In a hatching experiment, mortality was first observed at pH 13, when all fertilized eggs died within 8 min, followed by pH 2 (30 min), pH 12 (60 min), pH 3 (4 h), and pH 11 (5 h). Hatching only occurred at pH 4-10, with the highest hatching rate at pH 7 (52%) and the lowest at pH 10 (24%). Hatching rates in acid solutions were higher than in alkaline solutions, although the difference was not significant. Hatching was first observed at pH 10, beginning 27 h after fertilization and ending at the 31 h. A clear difference was observed between hatching times, ranging from 31 to 64 h and increasing in order with descending pH.

• Fisheries and Aquatic Sciences
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• v.15 no.2
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• pp.177-181
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• 2012

To understand the effects of lower pH levels due to elevated $CO_2$ and salinity, we designed and constructed a pH-control system that included automatic $CO_2$ infusion and measured the hatching rate of a crustacean model species, Artemia franciscana. The pH-control system was cost-effective and capable of performing animal tests in which pH fluctuated around $8.0{\pm}0.1$, with the temperature around $27{\pm}0.5^{\circ}C$. Hatching rate was observed under four different pH levels (7.0, 7.3, 7.6, and untreated control) combined with three salinity ranges (15, 25, and 35 ppt). The results demonstrated that lower pH levels led to decreased hatching rates regardless of salinity, and the minimum hatching rate was detected at pH 7.0 compared to the control (pH $8.0{\pm}0.1$), supporting the idea that OA has adverse effects on hatching rates and increases the risk of juveniles being introduced in the ecosystem. In contrast, salinity changes exhibited no synergistic effects with pH and had independent effects.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.4
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• pp.486-491
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• 2020

This study was investigated the survival and hatching rate of fertilized eggs in olive flounder Paralichthys olivaceus at water temperature, salinity, duration of transport and different stock densities during commercial transport. The observed optimal temperature during transport was 17.5℃ similar to the natural environmental conditions. The proper salinity was observed to be at 33 psu (practical salinity unit) in both surviving and hatching rate. In terms of the duration of transport, there were no differences until 12 hours between survival and hatching rate, but shorter time of transport would be better. With the best conditions during transport, 20,000 eggs/L were handled in both survival and hatching rate. These results can be essential in the production and transport of healthy olive flounder seeds.

• Journal of Aquaculture
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• v.12 no.1
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• pp.25-30
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• 1999

This study was carried out to produce the seedling of the larvae and juveniles of pale chup, Zacco platypus (Cyprinidae) in terms of artificial hatching, feeding behavior and growth rates. The total lengths of the newly hatched larvae were 7.6~8.2mm (mean: 7.97mm). The hatched larvae rose to the surface 3 days after hatching. The larvae were fed Daphnia, rotifer, Artemia and powdered feed. Hatching experiments were conducted in jar incubators under the different water temperature conditions, $20~32^{\circ}C$. The highest hatching rate was at $26^{\circ}C$ after 47 hours. Jar incubators was the highest hatching rate (89%), and cage and Californian incubators were useful and relatively high hatching rates (>89%). The size of the larvae 50 days after hatching were 30.0mm (25.6~32.0mm). As the water temperatures was increased, the growth rate of the larvae was also increased. Especially, the growth rates were favorable over $26^{\circ}C$, but survival was the worst at $32^{\circ}C$. This species was quick to accept assorted feed after hatching. The assorted feeds for flounder and rockfish better than that of carp in reference to growth rate.

• Ocean and Polar Research
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• v.35 no.3
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• pp.239-247
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• 2013

Digital image processing is a process to analyze a large volume of information on digital images. In this study, Artemia hatching rate was measured by automatically classifying and counting cysts and larvae based on color imaging data from cyst hatching experiments using an image processing technique. The Artemia hatching rate estimation consists of a series of processes; a step to convert the scanned image data to a binary image data, a process to detect objects and to extract their shape information in the converted image data, an analysis step to choose an optimal discriminant function, and a step to recognize and classify the objects using the function. The function to classify Artemia cysts and larvae is optimally estimated based on the classification performance using the areas and the plan-form factors of the detected objects. The hatching rate using the image data obtained under the different experimental conditions was estimated in the range of 34-48%. It was shown that the maximum difference is about 19.7% and the average root-mean squared difference is about 10.9% as the difference between the results using an automatic counting (this study) and a manual counting were compared. This technique can be applied to biological specimen analysis using similar imaging information.

• Journal of Aquaculture
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• v.9 no.4
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• pp.339-344
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• 1996

The effect of temperature ($24\~36^{\circ}C$ and salinities ($5\~30$ ppt) on hatching rate of the resting egg of the Korean rotifer, Brachionus plicatilis was investigated. The highest hatching rate of the resting egg was $85.7\%$ at $28^{\circ}C$ and 15 ppt. The hatching rates of the resting eggs with salinities were not significant at $326{\circ}C$ and $36^{\circ}C$. Hatching was faster at higher temperature. The resting eggs stored at $5^{\circ}C$ in dark hatched simultaneously within two days, however, those at $28^{\circ}C$ in dark hatched intermittently within 14 days. But, final hatching rate of the resting egg at $28^{\circ}C$ was higher at $28^{\circ}C$ than that at $5^{\circ}C$. With regard to drying temperature and time of resting egg, the resting egg dried at $30^{\circ}C$ for 1 hour showed the highest hatching rate ($46.4\%$).

• Korean Journal of Ichthyology
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• v.22 no.3
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• pp.195-200
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• 2010

A large volume of hatching jar was tested whether it is an effective to hatch fertilized eggs of Pacific cod. The volume of hatching jar did not show any significant differences in survival of the fertilized eggs; 48.3% for the jar of 15 L and 50.4% for that of 42 L. Survival rate of the fertilized eggs in a large volume of hatching jar ranged from 40.0 to 71.2%, which was higher than those of conventional small circular tank. A higher survival could be achieved even though stocking density of fertilized eggs was as high as 5,000 mL/jar. Consequently, the tested hatching jar allowed for incubation of a greater number of eggs with higher survival rate in a much smaller space. In addition, it reduces costs and manpower, and requires a relatively small amount of water per individual unit (6,700 mL/min), and provides a way to incubate multiple rearing groups in a quarantine environment.

• Korean Journal of Poultry Science
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• v.27 no.3
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• pp.181-187
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• 2000

This work was designed to investigate the performances of broiler breeder hens upon the addition were vitamin and mineral supplements in feeds. Animals were divided into for feed groups such as control, T$_1$,T$_2$and T$_3$, and each treatment has four replications. All broiler breeder hens were housed individually, and were fed with identical iso-metaboilic energy and iso-protein, except for vitamins and minerals. Different sources and levels of vitamins and minerals were added to the basic feeds according to the treatments. At the end of the experiments, general laying rate(hen days), average egg weight, hatching egg laying rate(Hen day) every day. Hatching egg weight, sterility, embryo mortality, hatching rate and chick weight were examined. Although, early laying rate in all treatment groups were reduced during cold term management, general egg laying rate was increased only T$_3$group which was contanining vitamin C. However, similar results were obtained in the rates of general and hatching egg laying. General egg laying rate were somewhat higher of Control, T$_2$and T$_3$ groups than that of T$_1$group. In addition, the laying rates of general and hatching eggs slightly improved in the T$_3$group rather than those of Control group. Egg weight was reduced with the increasing of laying rate, showing the highest in the T$_3$group. The laying rate showed significantly lower value than those of any other groups. Egg weight was about 65g in T$_3$group. The results of hatching performance for production ability of Broiler breeder hens were fed experimental diet, although the rates of non-hatched and hatched eggs increased in order of Control, T$_1$T$_2$and T$_3$groups. However, the rate of embryo mortality was declined in order Control, T$_1$T$_2$and T$_3$groups.