• The Korean Journal of Malacology
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• v.29 no.4
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• pp.313-323
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• 2013

Gonad development, the reproductive cycle, first sexual maturty and size at 50% of group sexual maturity (the biological minimum size) of Gomphina (Macridiscus) veneriformis were investigated for clams collected from the coastal waters of Donghae City, the East Sea of Korea by histological, and morphometric analysis. Monthly variations of the gonad index showed a pattern similar to that of the reproductive cycle. The reproductive cycle with the gonad developmental stages in female and male G. (M.) veneriformis can be classified into five successive stages: early active stage (December to March), late active stage (March to June), ripe stage (June to July), partially spawned stage (June to August), and spent / inactive stage (September to December). The spawning period continued from June to August, with a peak between July and August when the seawater temperature exceeds $20^{\circ}C$. The percentages of first sexual maturities of female and male clams ranging from 25.1 to 30.0 mm were 56.3% in females and 61.1% in males, and for clams over 30.1 mm shell length, it was 100%. Shell lengths at 50% of group sexual maturity (biological minimum size, $RM_{50}$) were 27.71 mm in females and 26.31 mm in males. Because harvesting clams < 26.31 mm in shell length could potentially cause a drastic reduction in recruitment, a measure indicating a prohibitory fishing size should be taken for adequate fisheries management.

• Korean Journal of Ecology and Environment
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• v.33 no.4 s.92
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• pp.395-404
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• 2000

The gonadosomatic index (GSI), hepatosomatic Index (HSI), egg size distribution, gonad development and reproductive characteristics of venus fish, Aphyocypris chinensis, were examined during March 1997- March 1998 in agricultural waterways of the Sedo-myun, Puyo county, Chungnam Province, Korea. Annual reproductive cycle was classified into the following five successive phases by monthly changes in GSI and the characteristics of ovary: quiescent phase (January- February), secondary growing and mature phase (March-May), ripe and spawning phase (June-July), degenerating and resting phase (August-September) and primary growing phase (October-December). The hepatosomatic index (HSI) showed clear seasonal pattern with two separate peaks. However, it exhibited a negative correlation to changes of GSI values. The regression analysis suggested that fecundity showed a strong positive linear relationship ($r^2\;=\;0.91$, n = 34) with body weight. The sex ratio of female to male was 1.4 : 1 in the natural population during the study. The minimum reproductive size of female and male venus fish was 38 mm and 33 mm in fork length, respectively.

• The Korean Journal of Malacology
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• v.27 no.1
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• pp.43-53
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• 2011

The gametogenic cycle and the spawning season in female and male Cyclina sinensis were investigated by quantitative statistical analysis using an image analyzer system, and the biological minimum size (the size at 50% of sexual maturity) was calculated by combination of quantitative data by size and von Bertalanffy's equation. Compared the gametogenic cycle by quantitative statistical analysis with the previous qualitative results in female and male C. sinensis, monthly changes in female and male gametogenic cycles calculated by quantitative statistical analysis showed similar patterns to the gonadal stages in female and male reproductive cycles by qualitative histological analysis. Comparisons of monthly changes in the portions (%) of each area to eight kinds of areas by quantitative statistical analysis in the gonads in female and male C. sinensis are as follows. Monthly changes in the portions (%) of the ovary areas to total tissue areas in females and also monthly changes in the portions of the testis areas to total tissue areas in males increased in March and reached the maximum in May, and then showed a rapid decrease from June to October. Monthly changes in the portions (%) of oocyte areas to ovarian tissue areas in females and also monthly changes in the portions of the areas of the spermatogenic stages to testis areas in males began to increase in March and reached the maximum in June in females and males, and then rapidly dropped from July to October in females and males when spawnig occurred. From these data, it is apparent that the number of spawning seasons in female and male C. sinensis occurred once per year, from July to October. Monthly changes in the number of the oocytes per mm2 and in the mean diameter of the oocyte in captured image which were calculated for each female slide showed a maximum in May and reached the minimum from December to February. Therefore, C. sinensis in both sexes showed a unimodal gametogenic cycle during the year. The percentage of sexual maturity of female and male clams ranging from 25.1 to 30.0 mm in length was over 50% and 100% for clams over 40.1 mm length. In this study, the biological minimum size (sexually mature shell lengths at 50% of sexual maturity) in females and males were 26.85 and 26.28 mm, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.1
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• pp.8-16
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• 1998

Sexual maturation and reproductive cycle of the goldeye rockfish, Sebastes thompsoni were investigated under photomicroscopy. Samples were collected monthly in the coastal water of Samcheonpo ($34^{\circ}55'N$ ), Korea from November 1995 to October 1996, The ovary consists of several ovarian lamellae originated from ovarian outer membrane. Oogonia which are originated from the inner surface of the ovarian lamella protrude to the ovarian cavity in oocyte stage, and they ave suspended by the egg stalk. The testis is seminiferous tubule type in internal structure. Seminiferous tubule consists of many testicular cysts which contain numerous germ cells in same developmental stage. Biological minimum size of female and male were 19.5 cm and 21.5 cm in total length, respectively. Gonadosomatic index (GSI) of female was the highest (9.56) in March and the lowest (0.15) in August. GSI of male was the highest (0.25) in February and the lowest (0.04) in July. Reproductive cycle was classified into the following successive stages: in female, growing (October and November), maturation ( $December\~February$), gestation (March), parturition and recovery ($April\~June$) and resting ($July\~September$), and in male, growing ($September\~November$), maturation ( December and January), ripe and copulation ( February and March) and degeneration and resting ($April\~August$).

• Journal of Aquaculture
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• v.20 no.4
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• pp.212-218
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• 2007

Reproductive biology (sexual maturity and reproductive cycle) of starry flounder Platichthys stellatus were examined by histological methods. From March 2004 to February 2005, 144 females and males were sampled. Gonadosomatic index (GSI) of female and male were peaked in May and February, respectively. Monthly changes of hepatosomotic index (HSI) showed a negative correlationwith those of the GSI. Changes of condition factor (CF) in female were correlated with gonad maturation, while that of male were no difference all the year round. Based on monthly GSI and gonadal development the reproductive cycle of starry flounder could be divided into four stages: growing stage (September to November), maturation stage (September to February), ripe and spent stage (March to May), and recovery and resting stage (June to August). Biological minimum size of female was 1,074 g. The relationship between fecundity (F) and body weight (BW) of the fish was expressed as $F\;=\;455.86BW^{1.2006}$.

• The Korean Journal of Malacology
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• v.28 no.2
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• pp.175-185
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• 2012

To clarify reproductive ecology of the melania snail Semisulcospira coreana (v. Martens, 1886) in Bukhan River, gonad development, fatness, gonad index, sex ratio, first sexual maturity of population, monthly change of larvae number and developmental stages in brood pouches were investigated by six identification methods. As maturation progrsses, the sex of the snali can be distinguishable easily by color:: the ovary being blue-green and testis light yellow. The sex ratio of female to male individuals over 13.95 mm shell height was significantly different from 1:1 (${\chi}^2$ = 38.45, p < 0.05). The sex ratio of female to male individuals changed drastically according to the season, Based on the monthly variations of fatness, gonad index and histological analysis, spawning occurred twice a year (spring and autumn) and the mean size of matured eggs was $450{\mu}m$ in diameter. The monthly change of larval number in brood pouch showed also two distinct peaks in March and September during the year. The average number of larvae in brood pouches was 286 - 862 individuals. In this study, the number of larvae in the brood pouches were a minimum in December and a maximum in March (975 larvae). The biological minimum size (the size at 50% of group sexual maturity) of the melania snail was 13.95 mm in shell height in females and males. All females over 15 mm in shell height possesed brood pouches.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.4
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• pp.627-633
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• 1997

Gonad structure, germ cell development and reproductive cycle of the smallmouth scorpionfish, Scorpaena miostoma were investigated based on histological method. Samples were collected monthly in the vicinity of Suyoung Bay, Pusan, Korea from November 1995 to October 1996. The testis is seminiferous tubule type in internal structure. Seminiferous tubule consists of numerous testicular cysts which contain numerous germ cells in same developmental stage. The ovary consists of several ovarian lamellae originated from ovarian outer membrane. Oogonia originated from the inner surface of the ovarian lamella protrude to the ovarian cavity in oocyte stage, and they are suspended by the egg stalk. Biological minimum size of female and male were 12.5cm in total length. Gonadosomatic index (GSI) of female (3.81) and male (0.23) were the highest in October. Reproductive cycle was classified into the following successive stages: in female, growing stage $(May\~August)$, maturation stage $(September\~October)$, ripe and spawning stage $(November\~December)$, recovery and resting stage $(January\~April)$, and in male, growing stage $(June\~August)$, maturation stage $(September\~October)$, ripe and spent stage $(November\~January)$ and recovery and resting stage $(February\~May)$.

• The Korean Journal of Malacology
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• v.17 no.1
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• pp.45-55
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• 2001

Gametogenes, reproductive cycle, first sexual maturity(biological minimum size), sex ratio and larval development of the marsh clam Corbicula japonica were investigated monthly by histological observations. Samples were collected in brackish water of Gokgang stream, Kyungsangbuk-Do, Korea, from August 1997 to July 1998. Sexuality of Corbicula japonica is dioecious and the species are an oviparous clam. The gonads are irregularly arranged from the sub-region of mid-intestinal gland in visceral cavity to reticular connective tissue of foot. The ovary is composed of a number of ovarian sac which are branched arborescent. Oogonia actively proliferate along the germinal epithelium of ovarian sac, in which young oocytes are growing. The testis is composed of a number of testicular tubules, and the epithelium of the tubule has function of germinal epithelium, along which spermatogonia actively proliferate. A great number of undifferentiated mesenchymal tissue and eosinophilic granular cells are abundantly distributed between developing oocytes and spermatocytes in the early developmental stages. With the further development of the ovary and testis these tissue and cells gradually disappear. Then the undifferentiated mesenchymal tissue and eosinophilic granular cells are considered to be related to the growing of the oocytes and spermatocytes. The spawning period is from July to September, and the main spawning occur between July and August when seawater temperatures reach above 22$^{\circ}C$. The reproductive cycle of this species can be divided into five successive stages; early active (February to April), late active (May to July), ripe (June to September), partially spawned (July to September), degenerative (September to October) and resting stage (October to February). Percentages of first sexual maturity of female and male clams ranging in length from 10 mm to 12 mm are over 50% and 100% for clams over 16.0 mm in shell length. Fertilized eggs or Corbicula japonica were 80-90 ${\mu}{\textrm}{m}$ in diameter. In the early embryonic development of C. japonica, the appearance of polar body, trochophore and D-shaped veliger were observed around 40 min., 27 hours and 4 days after spawning, respectively, at a water temperature of 26.5-28.$0^{\circ}C$. The size of larvae of early umbo stage was about 185-210 ${\mu}{\textrm}{m}$ in shell length, 160-180 ${\mu}{\textrm}{m}$ in shell height around 7 days after fertilization. The correlation of relative growth between the culture day (D) and shell length (SL) was expressed by the following simple formula from D-shaped veliger to metamorphosing stage; SL = 13.300D + 209.36($r^2$= 0.9078).

• Korean Journal of Environment and Ecology
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• v.25 no.1
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• pp.1-9
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• 2011

In order to analyze the change in home ranges depending on the reproductive stage of Pipistrellus abramus, radio-tracking was carried out for a total of 9 individuals, 3 individuals each, by dividing stages into a pregnancy stage, lactation stage, and post-lactation stage from May to August 2009. For radio-telemetry, 0.38g transmitters, R2000 receivers and 3-element Yagi antennas were used. Pipistrellus abramus were captured using a double-stacked mist net and a harp-trap. Analysis of home ranges used a SHP File and ArcGIS 3.3 for GIS, and used a Kernel Home Range Method(KHR) and a Minimum Convex Polygon(MCP) Method for analysis. Home ranges at the pregnancy stage were MCP 100% $13.46{\pm}1.84ha$, MCP 95% $12.28{\pm}2.15ha$, KHR 50% $3.00{\pm}0.71ha$, and home ranges at the lactation stage were MCP 100% $8.13{\pm}0.23ha$, MCP 95% $7.73{\pm}0.63ha$, KHR 50%$1.84{\pm}1.05ha$. Home ranges at the post-lactation stage were MCP 100% $125.58{\pm}97.77ha$, MCP 95% $123.89{\pm}97.73ha$, KHR 50% $28.61{\pm}26.78ha$. As a result, home ranges of pipistrellus abramus showed a significant difference in all of the MCP 100%, MCP 95%, KHR 50% depending on reproductive stages, being largest in the post-lactation stage and smallest in the lactation stage.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.6
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• pp.812-820
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• 2002

An experiment was conducted on 190 progeny (winter -74; summer -59; rainy -57) of 12 Grey Giant rabbits (10 female +2 males), to assess the effect of different seasons in a year, on their reproductive, growth and productive performances along with feed efficiency, under sub-temperate Himalayan conditions. The daily meteorological attributes recorded during winter (October to March), summer (April to June) and rainy (July to September) seasons, and analysed were minimum and maximum temperature, relative humidity and rainfall. Various biological parameters recorded were doe weights at mating and kindling, litter size at birth, litter weight at birth, kit mortality, litter size at weaning, litter weight at weaning, weekly body weight up to 98 d and weaner mortality. Individual weight gains, dressing percentages, meat weights, liver weights, raw-pelt weights, processed pelt weights and processed pelt areas at slaughter on d 84 and 98, respectively were also recorded. The feed and fodder compositions and their nutritive values during different seasons were also analysed. Average ambient temperature during winter, summer and rainy seasons were $13.2{\pm}2.8$, $22.4{\pm}3.7$ and $24.8{\pm}2.3^{\circ}C$, respectively. The average relative humidity and total rainfall for winter, summer and rainy seasons were $68.9{\pm}1.5$% and $48{\pm}26.6$mm, $66.3{\pm}4.8$% and $125.6{\pm}56.8$ mm, and $77.3{\pm}1.3$% and $116.3{\pm}90.4$ mm, respectively. The weight of doe at mating and kindling, litter size at birth, litter weight at birth and litter size at weaning were comparatively higher whereas litter weight at weaning was significantly (p<0.05) higher during winter as compared to summer and rainy seasons. The kit mortality was significantly (p<0.05) higher during winter while the weaner mortality was significantly (p<0.05) higher during rainy season. At 84 d, the live weight per doe, slaughter weight, dressing percentage and liver weight were significantly (p<0.05) higher during winter than summer and rainy. Similarly, the gain in weight and meat weight at 84 and 98 d were significantly (p<0.05) higher during winter. The weight of raw pelt and processed pelt were recorded significantly (p<0.05) higher during winter while no difference in the area of processed pelts during different seasons could be observed. No difference in the biological performance could be observed between sexes in any of the seasons. Roughage analysis revealed comparatively higher crude protein percent and lower crude fibre percent during summer and rainy seasons than in winter. The roughage dry matter intake was comparatively higher during summer and rainy seasons vis-a-vis constant amount of concentrate supplied during all the three seasons. The digestibilities of dry matter was significantly (p<0.05) lower, whereas that of crude fiber, acid detergent fibre and cellulose were negative during winter. Interestingly, the feed:gain was exceedingly well during winter than in other seasons and it is concluded that it was the best season for production of rabbits under sub-temperate Himalayan conditions.