• Journal of Aquaculture
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• v.9 no.1
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• pp.25-42
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• 1996

The study has been conducted to know an appropriate feeding strategy and effects of the rearing density on larval growth of the rockfish, Sebastes schlegeli. The results obtained are as fellowed ; 1. Thirty-day-old larvae reached at $25.25{\pm}3.76$ mm in total length and $0.23{\pm}0.07$ g in body weight in experiment A, at which rotifer was provided from the beginning to the end of 30-day experiment, Anemia from 3th to 18th day, and artificial feed from 13th to 30th day after hatching. When rotifer was provided for 30 days, Artemia from 6th to 18th day, and artificial feed from 18th to 30th day after hatching (experiment B), these larvae grew up to $27.52{\pm}2.50$ mm in total length and $0.26{\pm}0.06$ g in body weight. On the other hand, when rotifer and artificial feed were supplied with the same time schedule as shown in experiment B, and Artemia was feed from 6th to 30th day after hatching (experiment C), the total length and body weight of those larvae were $23.22{\pm}3.44$ mm and $0.15{\pm}0.05$ g, respectively. The best result for larval growth was obtained from experiment B. The survival rates estimated were $57.6\%$ in experiment A, $66.4\%$ in experiment B, and $44.4\%$ in experiment C. 2. The growth in total length of the larvae according to their rearing days could be represented by the following equations : Experiment A : Y=4.350+0.116X+$1.887X^2$ (r=0.993) Experiment B : Y=4.500+8.931X+$2.221X^2$ (r=0.994) Experiment C : Y=4.478+5.734X+$1.881X^2$(r=0.990) The average number of Artemia nauplius intaken by the larvae was rapidly increased between 15th and 20th day afer hatching, and 9, 212, 242, 750, and 1,171 nauplius were found in the different sizes of larvae, whose total length were 5.65, 6.81, 9.45, 14.96, and 24.52 mm, respectively. 3. Larval growth in total length and body weight reared at four different densites (A: 1.8 $kg/m^3$, B; 4.0 $kg/m^3$, C; 5.0 $kg/m^3$, D; 6.2 $kg/m^3$) indicated that the best growth was found in experiment A, at which the larval were reared at the lower density and the final survival rates extimated were $92.9\%$ in exp. A, $99.5\%$ in exp. C, $89.0\%$ in exp. B, and $88.2\%$ in exp. D. The amount of production per cubic meter turned out to be 30.45 kg in exp. D, 25.89 kg in exp. C, 20.75 kg in exp. B and 10.48 kg in exp. A. therefore, considering both larval growth and survival rate, higher yields seemed to be attainable at the relatively high-rearing density.

• Korean journal of applied entomology
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• v.47 no.4
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• pp.385-394
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• 2008

Larvae of Monochamus saltuarius showed normal growth and development on conifers of Pinus koraiensis, P. densiflora, Abies holophylla, Larix leptolepsis, P. bungeana, and P. rigida, respectively, but the conifers influenced significantly the body weight and the survival rate of larvae. Though the larval body weights were in a wide spectrum among treatments, growth curves of them were very similar from each other, showing continuous increase from the early larval stage to about 3 months old. The body weight was decreased slightly after the feeding period of the early 3 months. The size of larvae and adults became the largest from P. bungeana fed larvae. The mid-sized ones were from P. koraiensis, P. densiflora and A. holophylla. Small ones came from L. leptolepsis and P. rigida. The larval growth was retarded without water supply. Overall survival rates from the early stage of a larva to a fertile adult were 53.6% from P. koraiensis; 51.8%, P. densiflora; 34.7%, A. holophylla; 17.8%, P. bungeana; 16.7%, L. leptolepsis; and 12.3%, P. rigida. Adults from larvae fed the 6 species of conifers, respectively, were grown into the reproductively potent adults, which laid viable eggs. A few of overwintered larvae did not pupate and remained still as a larva until the late October of the year. Data from the field survey, the head width emerged from P. koraiensis was larger than that of L. leptolepsis. The adult emergence hole in P. koraiensis was larger also. While, the size of the emergence hole was larger in the artificially innoculated log of P. koraiensis, which was kept for a larva to be with a minimized food competition and sufficient water supply, than that of the field.

• Journal of Aquaculture
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• v.13 no.1
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• pp.69-78
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• 2000

Bioactivity growth and survival rte of yolk sac larvae in cultured black seabream (Acanthopogrus schlegeli) red seabream (Pagrus major) and olive flounder (Paralichthys olivaceus) to 5 different concentration (0, 25, 50, 75 and 100%) of water soluble fraction (WSF) of Kuwait crude oil were studied. The 75% and 100% of WSF concentration influenced negatively on the length growth of larvae in each species so the growth rates of total length in the concentration of WSF were significantly lower than those of control. The high concentration (50%, 75%, and 100%) of WSF influenced negatively not only on the swimming frequency and speed but also on the morphological abnormality of larvae. Red seabream larvae showed the highest rate of abnormality by WSF among the tested fishes. The fish larvae exposed during pre-and post-hatch (egg and larval stages) and during post-hatch (larval stage only) to the WSF were significantly influenced on their survival rate. The larvae of red seabream were more sensitive to WSF than those of black seabream and olive flounder. The survival rates of larvae exposed to higher concentration (50%, 75%, and 100%) of WSF were significantly lower than those of the control but those of the 25% group were not.

• Korean Journal of Ichthyology
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• v.7 no.1
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• pp.25-32
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• 1995

The larval fish, which had been previously identified or classified as Enedrias (Pholis) nebulosus, Enedrias spp., Pholis taczanowskii, and unidentified species belonging to Protosalanginae, were revealed as that of a gunnel, Enedrias fangi. This species has been known as a cold water species mainly caught in the Yellow Sea. Larval E. fangi showed peak abundances in the coastal waters off Chonlla Province in March, Chungnam Province in April, and Kyunggi Province in May and June. The primary spawning season of E. fangi seemed to be winter (November to January), and the eggs hatched after 60 days from spawning. The average growth rate of larval fish was about 0.33mm/day. The larval fish of 40mm in body length began to move to the bottom, and stayed in the bottom cold water mass when their body length was greater than 60-70mm. The average annual catches of larval E. fangi from 1985 to 1991 were 5,000M/T in the Yellow Sea, which were more than 99 % of the total gunnel catches around Korean waters. The peak season of catches was from March or April to July in Chungnam Province, and from May to July in Kyunggi Province.

• Development and Reproduction
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• v.23 no.1
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• pp.35-42
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• 2019

Fish shows great difference in growth rate between individuals during larval development and early growth. This difference seriously reduces the production efficiency in fish culture. Growth hormone (GH)/Insulin-like growth factor 1 (IGF1) system is said to play some pivotal roles in fish growth. In this study, we investigated differences of GH, IGF1 and GHR gene expressions in juvenile red spotted grouper (Epinephelus akaara) with different growth performance. Red spotted groupers were reared under the same environmental condition (water temperature $24{\pm}1^{\circ}C$, natural light) for 96 days after hatching. They were divided into 3 groups by size (fast growing, middle growing and slow growing groups: FGG, MGG, and SGG, respectively). RNA was extracted from the brain, liver and muscle tissues from each group, and target gene expression was examined by real-time PCR. In the brain with pituitary gland, expression of GH gene in FGG was significantly higher than the expression in SGG, but the expression of IGF1 and GHR genes in the muscle was highest in SGG. Difference of GHR and IGF1 mRNA in the liver between groups with different growth performance was less clear than that in other tissues, although level of IGF1 mRNA was higher in SGG than in MGG. These results suggest that hormonal governing of growth is not the same in fast growing and slow growing fish, and size grading could cause a shift of hormonal state and growth pattern in this species.

• Korean Journal of Environmental Biology
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• v.29 no.4
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• pp.379-387
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• 2011

Copepod nauplii plays an important role as a linker between the microbial food web and classical food chain in marine ecosystem and is an essential food source for early stage of many larval fishes. Study on the influencing factors on the growth of copepod naupliar stages has been rarely carried out in despite of these ecological significances. Many studies have shown that food availability and temperature are major factors to influence copepod growth. However, due to the complicated environment parameters in coastal ecosystem, the relationships between growth of copepods and influencing factors are still unclear under the natural condition. Growth rates of the copepod $Acartia$ $hongi$ nauplii were measured in Kyeonggi Bay from February to December 2001. $Acartia$ $hongi$ is numerically abundant and widespread predominant species in the coastal regions of the Yellow Sea and occurs continuously throughout the year, with a maximum peak in late spring. The naupliar growth rates of $Acartia$ $hongi$ by the artificial cohort method varied from 0.03 to 0.18 $day^{-1}$, with a mean of 0.09 $day^{-1}$. The overall naupliar growth rates showed a significantly positive relationship with the variation in water temperature. However, Previous study reported that the growth rates of adult $Acartia$ $hongi$ were primarily influenced by the variation in chlorophyll-$a$. Therefore, these differences demonstrated that the influencing factors of growth did not correspond with the developmental stages. The results of this study suggest that the dissimilarity of growth between nauplius and adult female resulted from the size-dependant difference in food availability and the growth of older developmental stages containing adults are more food-dependent than juveniles.

• Development and Reproduction
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• v.10 no.4
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• pp.271-275
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• 2006

The objective of this study was to examine the early growth of haddock, Melanogrammus aeglefinus larvae from a series of reared specimens for provide information to developmental biology and more information on the aspect of aquaculture in the larvae of this species. Larvae were reared in the laboratory and sampled periodically for developmental study until 67 days after hatching. An increase in total length of fish indicated continuous growth, described by the growth expression of the type $TL=3.5374e^{0.0536X}(r^2=0.8759$, where TL is total length and X is at days after hatching) and $BW=0.0002e^{0.1858X}(r^2=0.8671$, where BW is body weight and X is at days after hatching), respectively. Pattern of body depth and pectoral fin length are instantaneous growth which expression of the type $BD=0.3545e^{0.0778X},\;r^2=0.9563$(where BD is body depth and X is at days after hatching) for body depth growth and the type $PL=0.0111e^{0.1591X},\;r^2=0.9194$(where PL is pectoral fin length and X is at days after hatching) for pectoral fin length growth. The relationship of body depth and total length expressed as $BD=0.2397X-0.5735(r^2=0.9957$, where BD is body depth and X is total length), and pectoral fin length and total length is $PL=0.1929X-1.3767(r^2=0.9882$, where PL is pectoral fin length and X is total length) pectoral fin length against body depth simultaneously recorded for juvenile haddock(PL=0.8117BD-0.9718, $r^2=0.9814$, where PL is pectoral fin length and BD is body depth). Relationship of body depth and body weight was expressed the type of $BD=-9.4734X^2+19.046X+1.3672,\;r^2=0.941$(where BD is body depth and X is body weight), and pectoral fin length and body weight expressed the type of $PL=6.379X^2+14.023X+0.3774,\;r^2=0.9494$(where PL is pectoral fin length and X is body weight). From this point view, growth characteristics of juvenile haddock in this experiment may be useful to establish a successful culture technique for rearing larval haddock.

• Journal of Environmental Health Sciences
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• v.28 no.4
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• pp.17-22
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• 2002

In crustaceans, as in other arthropods, the molt cycle and the physiological process of growth are controlled by molting hormones (MH) which are steroid hormones, the ecdysteroids. Ecdysteroids are major arthropod hormones which control both development (embryonic and larval molts, metamorphosis) and reproduction. The purpose of the present study was to evaluate both fenarimol and methoprene for embryotoxicity to daphnids. The embryotoxicity associated with each compound was assessed to discern whether the embryotoxicity of methoprene might be due to ecdysone agonist and the ecdysone antagonistic effects of fenarimol on Daphnia embryo. Exposure of daphnids for three weeks to 50 M methoprene resulted in a significantly high incidence of offspring that exhibited general toxicity. This exposure concentration had significant effects on the overall number of embryo death. However, exposure to 3 or 1 $\mu$M fenarimol were no significant effects on the embryo toxicity. The incidence of both of these toxicity increased with methoprene exposure. This observation suggest that methoprene showed embryonic general toxicity during embryo development, while, only fenarimol showed weak general toxicity with early stages of embryonic development.

• Fisheries and Aquatic Sciences
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• v.7 no.4
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• pp.192-203
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• 2004

The effects of temperatures, starvation, and kind of foods on growth, RNA/DNA ratio and protein contents during metamorphosis and early juvenile stage of olive flounder (Paralichthys olivaceus) were examined. During metamorphosis, warm-acclimated fish showed higher RNA and DNA content than those of the cold-acclimated fish, excepting H stage (28 DAH) at which the ratio was higher at cold temperature. RNA/DNA ratio during metamorphosis showed similar values at two temperatures tested. However, after 42 DAH warm-acclimated juveniles had higher DNA content compared with cold-acclimated fish, resulted in marked decreases in RNA/DNA ratios. Higher RNA content at H stage of cold-acclimated fish was consistent with an increase in protein content. Growth of fish rearing at warm temperature was higher than those of fish at cold temperature during all experiments. In starvation experiment, contents of DNA, RNA and protein significantly decreased. Even though there were no significant differences in total length (TL) and body weight between the live mysid-fed and artificial pellet-fed fish at 35 mm TL, both RNA/DNA and protein/DNA ratios of the former group was significantly higher than those of the latter due primarily to lower DNA content of the live mysid-fed group. The results from this study suggest that temperature, starvation and kind of foods should be considered when RNA/DNA ratio applied to assessing the cultured larval and juvenile fish condition.

• Fisheries and Aquatic Sciences
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• v.18 no.3
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• pp.301-309
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• 2015

Chub mackerel, Scomber japonicus, larvae and juveniles were reared from hatching to 35 days after hatching (DAH), and the development of their digestive systems was histologically investigated. The larvae were initially fed on rotifers and Artemia nauplii starting around 19 DAH, and thereafter on Artemia nauplii, fish eggs, and a formulated feed mixture. The primitive digestive system differentiated at 3 DAH; the digestive tract was distinctively divided into the buccopharyngeal cavity, esophagus, stomach, air bladder, intestines, and rectum. The gastric gland and pyloric caeca first appeared at 5 and 7 DAH, respectively. The stomach was divided into cardiac, fundic, and pyloric regions in the preflexion phase. The number of gastric glands and pyloric caeca, as well as the volume of the gastric blind sac increased markedly, with development continuing into the juvenile stage. The precocious development of the digestive system during the larval period might be related to the early appearance of piscivory, which is able to support high growth potential. The organogenesis results obtained for this precocial species represent a useful tool to aid our understanding of the physiological requirements of larvae and juveniles to ensure optimal welfare and growth under aquaculture conditions, which will improve current rearing practices of this scombrid species.