• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.5
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• pp.642-647
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• 2016

Postlarval and juvenile anchovies Engraulis japonicus were collected using a gape net with wings in the coastal waters of Yeosu in July and August 2015, and their gut contents were analyzed. The size range of the postlarvae was 11.0-24.2 mm (notochord length) and that of the juveniles was 25.1-37.4 mm (standard length). Guts were empty in 64.5% of postlarvae and in 51.7% of juveniles. The dominant prey organisms in the guts of both postlarvae and juveniles were copepoda. Calanoida were important prey organisms for postlarvae and were dominated by nauplii of Paracalanus sp. and Calanus sp. as well as unidentified copepod naupill. Calanoida were also important in the diets of juveniles, whose gut contents were dominated by Paracalanus sp. and Cirripedia. Gut compositions were significantly different (P<0.05) among three body size levels in postlarvae and juveniles. As the body size of the postlarvae and juveniles increased, Calanoida constituted a larger proportion of the gut contents, while the proportion of copepod nauplii decreased.

• Fisheries and Aquatic Sciences
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• v.26 no.11
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• pp.649-659
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• 2023

The present study compared the structure of mixilliped of Fenneropenaeus chinensis between the larval and adult stage and investigated the effect of the structural difference on the immunity of F. chinensis. A fourteen day and a one-month long culture trial were conducted each with postlarvae and adults of F. chinensis in the biofloc, mixed water (50% biofloc:50% clear seawater) and seawater control. Immune-related genes mRNA expressions of postlarvae was analysed by quantitative reverse transcription polymerase chain reaction (qRT-PCR). And the analysis of adult stage immunity was carried out using phenoloxidase (PO) enzyme activation in haemocyte. In the postlarvae, the final body weights were 51.43 and 58.47 mg for the biofloc water and the control seawater, respectively. On the other hand, the final body weights of the adults were significantly different between biofloc water and seawater. The survival rate showed the opposite trend to the growth rate. Immune related genes mRNA expression levels in the postlarvae in the biofloc water were significantly lower than those in the seawater. While, the adult stage showed significantly higher PO enzyme activations in the biofloc water than in the seawater with the PO enzyme activation increasing proportionally to the biofloc concentration. This result is considerably explained by the observations of setal morphological structures of the third maxilliped: postlarvae have short serrulated setae that compose the small 'net' structure while adults had long and dense plumose setae. It is understood that the morphological difference of the maxilliped structure resulted in the different feeding abilities in the postlarvae and the adult F. chinensis to use bioflocs as food source.

• Journal of Aquaculture
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• v.5 no.1
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• pp.29-67
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• 1992

Life cycle and seed production of the freshwater prawn, Macrobrachium nipponense, were studied and the results are as follows : 1. Larval development : Embryos hatched out as zoea larvae of 2.06 mm in mean body length. The larvae passed through 9 zoea stages in $15{\~}20$ days and then metamorphosed into postlarvae measuring 5.68 mm in mean body length. Each zoea stage can be identified based on the shapes of the first and second antennae, exo- and endopodites of the first and second pereiopods, telson and maxillae. 2. Environmental requirements of zoea larvae : Zoea larvae grew healthy when fed with Artemia nauplii. Metamorphosing rate was $65{\~}72{\%}$ at $26{\~}28\%$ and $7.85{\~}8.28\%_{\circ}Cl.$. The relationship between the zoeal period (Y in days) and water temperature (X in $^{\circ}C$) is expressed as Y=46.0900-0.9673X. Zoeas showed best survival in a water temperature range of $26{\~}32^{\circ}C$ (optimum temperature $28^{\circ}C$), at which the metamorphosing rate into postlarvae was $54{\~}72\%$ The zoeas survived more successfully in chlorinity range of $4.12{\~}14.08{\%_{\circ}}Cl.$, (optimum chlorinity $7.6{\~}11.6\;{\%_{\circ}}Cl.$.), at which the metamorphosing rate was $42{\~}76{\%}$. The whole zoeal stages tended to be longer in proportion as the chlorinity deviated from the optimum range and particularly toward high chlorinity. Zoeas at all stages could not tolerate in the freshwater. 3. Environmental requirements of postlarvae and juveniles : Postlarvae showed normal growth at water temperatures between $24{\~}32^{\circ}C$ (optimun temperature $26{\~}28^{\circ}$. The survival rate up to the juvenile stage was $41{\~}63{\%}$. Water temperatures below $24^{\circ}C$ and above $32^{\circ}$ resulted in lower growth, and postlarvae scarcely grew at below $17^{\circ}C$. Cannibalism tended to occur more frequently under optimum range of temperatures. The range of chlorinity for normal growth of postlarvae and juveniles was from 0.00 (freshwater) to $11.24{\%_{\circ}}Cl.$, at which the survival rate was $32{\~}35\%$. The postlarvae grew more successfully in low chlorinities, and the best growth was found at $0.00\~2.21{\%_{\circ}}Cl.$. The postlarvae and juveniles showed better growth in freshwater but did not survive in normal sea water. 4. Feeding effect of diet on zoea Ilarvae : Zoea larvae were successfully survived and metamorposed into postlarvae when fed commercial artificial plankton, rotifers, and Artemia nauplii in the aquaria. However, the zoea larvae that were fed Artemia nauplii and reared in Chlorella mixed green water showed better results. The rate of metamorphosis was $68\~{\%}75$. The larvae fed cow live powder, egg powder, and Chlorella alone did not survive. 5. Diets of postlarvae, juveniles and adults : Artemia nauplii and/or copepods were good food for postlarvae. Juveniles and adults were successfully fed fish or shellfish flesh, annelids, corn grain, pelleted feed along with viscera of domestic animals or fruits. 6. Growth of postlarvae, juveniles and adults : Under favorable conditions, postlarvae molted every five or six days and attained to the juvenile stage within two months and they reached 1.78 cm in body length and 0.17 g in body weight. The juveniles grew to 3.52 cm in body length and 1.07 g in body weight in about four months. Their sexes became determinable based on the appearance of male's rudimental processes (a secondary sex character) on the endopodites of second pereiopods of males. The males commonly reached sexual maturity in seven months after attaining the postlarvae stage and they grew to 5.65 cm in body length and 3.41 g in body weight. Whereas the females attained sexual maturity within six to seven months, when they measured 4.93 cm in body length and 2.43 g in body weight. Nine or ten months after hatching, the males grew $6.62{\~}7.14$ cm in body length and $6.68{\~}8.36$ g in body weight, while females became $5.58{\~}6.08$ cm and $4.04{\~}5.54$ g. 7. Stocking density : The maximum stocking density in aquaria for successful survival and growth was $60{\~}100$ individuals/$\ell$ for zoeas in 30-days rearing (survival rate to postlarvae, $73{\~}80{\%}$) ; $100{\~}300$ individuals/$m^2$ for postlarvae of 0.57 cm in body length (survival rate for 120 days, $78{\~}85{\%}$) ; $40{\~}60$ individuals/$m^2$ for juveniles of 2.72 cm in body length (survival rate for 120 days, $63{\~}90{\%}$) : $20{\~}40$ individuals/$m^2$ for young prawns of 5.2 cm in body length (survival rate for 120 days, $62\~90{\%}$) ; and $10\~30$ individuals/$m^2$ for adults of 6.1 cm in body length (survival rate for 60 days, $73\~100{\%}$). The stocking density of juveniles, youngs and adults could be increased up to twice by providing shelters.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.1
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• pp.27-31
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• 2001

To investigate the food organisms and feeding selectivity of the white croaker (Argrosomus argentatus) during the postlarval stage, the gut contents of the postlarvae, captured in Kwangyang Bay in 1995, were observed, The food organisms were composed of copepod egg and nauplius, Codonellopsis sp. and Tintinnopsis spp. The indices of relative importance indicated that the most dominant food item was a copepod nauplius. As white croaker larvae grew, the size of prey items and the selectivity for copepod nauplius increased.

• Proceedings of the Korean Society of Life Science Conference
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• 2008.10a
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• pp.27.1-27.1
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• 2008

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.2
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• pp.136-143
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• 2003

The eggs of Favonigobius gymnauchen attached on the under side of a small stone were collected off Seongsan-eup Cheju-do in August, 2000 to investigate their development of egg, larvae and juveniles. The fertilized eggs were elliptical in shape (mean long axis: 1.50 mm; mean short axis: 0.57 mm) and transparent. There were filaments on one side of the egg membrane. Larvae hatched at 48 hrs 50 mins after morula stage with 25-26 myotomes in $22.8-28.5^{\circ}C\;(mean\;24.7^{\circ}C).$ The newly hatched larvae were 2.31-2.49 mm (mean 2.37 mm n=10) in total length (TL) and their mouth and anus were already opened. Their melanophores were appeared on the over gas globule, around anus and the part of caudal peduncle with 24-25 myotomes. At 4-5 days after hatching. larvae attained 3.81-4.07 mm (mean 3.96 mm, n=10) in TL and their yolk sac was completely absorbed. They began to eat rotifer and transformed to postlarvae stage. At 14 days after hatching, postlarvae attained 6.17-6.31 mm (mean 6.21 mm, n=10) in TL and their caudal notocord was flexed $45^{\circ}$ upward. At 24 days after hatching, postlarvae attained 8.69-9.10 mm (mean 8.87 mm, n=10) in TL had reached the juvenile stage. All fins were formed with the complete set of fin rays with the following counts: dorsal fin rays IV-I, 9-10; anal fin rays I, 9; pectoral fin rays 17; ventral fin rays: I, 5; caudal fin rays: 9+8= 17.

• Korean Journal of Environmental Biology
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• v.36 no.3
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• pp.377-384
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• 2018

This study focused on the effects of feeding on postlarvae of shrimp, Litopenaeus vannamei, during the identified acclimation time to low salinity. A total of 5 different salinity groups with or without feeding (32, 24, 16, 8, and 2 psu, 1 liter, triplicates) were prepared, and 30 shrimp were settled at PL21 (postlarvae) and placed in each group. After 24 hours of the experimentation process, the survival rate of the fed and starved groups was observed to be lower in the 2 psu group compared to other salinity groups, with the rate of 86.6% and 81.1%, respectively. The condition index of glucose and triglyceride, which are important factors for osmoregulation and as energy sources, was 4.2-7.6 times and 2.7-3.4 times higher in the fed groups than the starved groups at all the levels of salinities. The creatine level increased by 1.1-1.5 times in the starved groups as compared to the fed groups. Likewise, the activity of all the digestive enzymes like, lipase, ${\alpha}$-amylase, trypsin, and alkaline protease were clearly higher in the fed groups (ANOVA, p<0.05). Apparently, it was observed that feeding is effective for the postlarvae of shrimp, which shows a characteristic fast metabolism and larval development, during the acclimation period to low salinity.

• Development and Reproduction
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• v.18 no.4
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• pp.259-266
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• 2014

The egg development and early life history of Korean spotted sleeper, Odontobutis interrupta which is Korean endemic species from Sora-choen was investigated. The Korean spotted sleeper were caught at Sora-myeon, Yeosu-si, Jeollanamdo, from Korea at May in 2014. The fertilized eggs were $4.23{\pm}0.05mm$ in long diameter and had oil globules. Hatching time of the embryo began about 442 hr 14 min after fertilization under water temperature of $19.5^{\circ}C$. The newly hatched larvae were $4.27{\pm}0.35mm$ in total length and their anus were not yet opened. 3 days after hatching postlarvae was measured $6.20{\pm}0.11mm$ in total length. 10 days after hatching postlarvae was measured $6.69{\pm}0.14mm$ in total length.

• Korean Journal of Ichthyology
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• v.13 no.1
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• pp.63-68
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• 2001

The skeletal development of the larvae and juvenile of red marbled rockfish, Sebasticus tertius (Barsukov et Chen) was studied based on individuals that were discharged and reared in the laboratory from April to May 1997. In 8 days after bearing, the postlarvae attained 4.42 mm in total length (TL), and its parasphenoid, premaxillary, maxillary, and clavicle were ossified for the first time at this stage. In 15 days after bearing, the postlarvae attained 5.23 mm in TL, and its pterotic, basioccipital, exoccipital, opercle, and preopercle were ossified, with one spine on the each cranium and preopercle. In 27 days after bearing, the postlarvae attained 8.81 mm in TL, its vertebra were posteriorly ossified to the 15th centrum, and five spines were formed on the preopercle. In 39 days after bearing, the juveniles attained 14.21 mm in TL, and the all bones were almost completed at this stage.

• Ocean and Polar Research
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• v.41 no.4
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• pp.233-250
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• 2019

A re-assessment of the age structure of the population of the Antarctic icefish Pseudochaenichthys georgianus based on body length data covering the years 1976-2009 and including larvae and postlarvae collected in 1989 and 1990 allowed us to define age groups 0, I, and II as containing fish with respective body lengths of 6-9 cm, 15-27 cm and 27-39 cm. Age at maturity (first spawning) was found to occur in age group III at body lengths that have been falling from 50.1 cm in 1979 to 45.4 cm in 1992. Considering postlarvae together with adult fish, the v. Bertalanffy growth curve parameters were determined as L_∞ = 60.62 cm, k = 0.4, t₀ = 0.25. Although the reasons for a maturity at shorter body lengths is not fully understood a host of environmental factors like increasing water temperatures and possibly changes in currents, interspecific competition, food availability, etc. are likely to be involved. Global warming (and not primarily overfishing) is likely to have been responsible for the disappearance of larger fish in the surface waters of South Georgia since 1977, for virtually all commercial fishing stopped in the early 1990s. On the other hand, the appearance of numerous younger spawning individuals suggests that larvae do survive in the colder deeper water below 200 m. The biomass of Ps. georgianus oscillates with a 4-year periodicity in contrast to that of the coexisting icefish Chaenocephalus aceratus: the former with a lower biomass in warm years and a higher one in cold years. The biomass of the third species of icefish in the region, i.e. Champsocephalus gunnari, also oscillates, but with a longer periodicity than that involved in the biology of the other two and its biomass increases in contrast to the other two species. The result is that the biomass all three species considered together is rather stable.