• Fisheries and Aquatic Sciences
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• 제26권3호
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• pp.224-233
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• 2023

This research was conducted at Langgur City, Southeast Maluku Regency, Maluku Province, Eastern Indonesia from November 2020 to February 2021 to study biological aspects of roundscads (Decapterus spp.) which consist of species composition, sex ratio, gonad maturation level, size distribution, length-weight relationship and condition factor. Samples were collected at traditional fish market in Langgur City. Fish samples collected at the market were put into cool box and then brought to the laboratory for further examination. Fish samples were identified, separated based on species, dissected to determine their sex and gonad maturation stage and then measured. Totally, there were 290 specimen collected which consist of five species namely Decapterus kurroides, D. macarellus, D. macrosoma, D. muroadsi and D. russelli. Sex ratio between male and female for all species showed 1:1. Gonad maturation level showed that stage I and II have higher percentage than stage III and IV indicates immature fish more dominant compare to mature one. Among five species found, D. macarellus has larger size while the smaller belongs to D. muroadsi. Results of length-weight relationship analysis showed that roundscads inhabiting Southeast Maluku waters have isometric and negative allometric growth pattern with relative condition factor around 1.00.

• 생태와환경
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• 제53권3호
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• pp.229-240
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• 2020

본 연구는 영산강·섬진강 수계에 위치한 16개 호소에 대해서 어류군집을 조사하고 호소별, 호소 규모별 어류군집 특성을 분석하였다. 조사 방법과 지점수는 환경부의 "생물측정망 조사 및 평가 지침"에 따라 이루어졌으며, 소형호, 중형호, 대형호로 구분하여 어류군집을 비교 분석하였다. 2018년(7개 호소)에서 2019년(9개 호소)에 이루어진 조사에서 총 13과 44종의 어류가 채집되었으며, 우점종은 치리(Hemiculter eigenmanni, RA, 32.9%), 아우점종은 블루길(Lepomis macrochirus RA, 31.4%)로 나타났다. 호소 규모에 따라 분석한 결과 소형호에서는 평균(±표준편차) 11±2.9종이 채집되었으며, 중형호는 14.3±2.1종, 대형호는 22.7±0.6종으로 호소의 규모가 커질수록 출현 종수가 증가하는 양의 상관성을 나타냈다. 호소 규모별 어류군집 요인은 총 6개 항목(총 종수, 총 개체수, 풍부도, 초식 성종 개체수 비율, 육식성종 개체수 비율, 외래종 종수)에서 차이를 보였다(P<0.05). 호소별 어류군집 유사도 분석결과 16개 호소가 60%의 유사도에서 5개 그룹으로 구분되었으며, 군집 유사도는 호소의 규모보다는 호소 간 거리, 수계, 호소의 발달 위치 및 환경유형이 영향을 미치는 것으로 나타났다. 본 연구는 국내 호소의 어류군집 구조 이해에 도움이 될 수 있으며, 특히 영산강·섬진강 수계의 호소 관리 및 정책 마련에 기초자료로 활용될 수 있을 것이다.

• 한국어병학회지
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• 제1권2호
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• pp.73-76
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• 1988

There prevailed lymphocystis disease with 1 to 2cm in size in the skin and pins of cultured Sebastes schlegeli in fish farms in Tongyoung-gun, Sanyang-myeon, Kon-ri from summer, 1987 to fall, 1988. Though there were some difference between each fish farm, this disease prevailed widely from immature fish to mature fish, less than 10cm to 30cm in body length with about 8 through 80% of infection rate. Sebastes schlegeli with the lymphocystis disease showed combined nipple-shaped mass by doubly, triply propagated lymphocystis. But the author considered that lymphocystis disease was not a direct cause of death of Sebastes schlegeli, the fish showed marked inflammation by seconary infection of pathogenic organisms.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2000년도 하계학술발표대회 논문집 제19권 1호
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• pp.233-236
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• 2000

The acoustical response of fish depends on size and physical structure na, most important, on the presence or absence of a swimbladder. Acoustic scattering models for swimbladdered fish represent a fish by an ideal pressure-release surface having the size and shape as the swimbladder. Target strength experiments of red seabream (Chrysophrys major) have been conducted using 38 (split-beam), 120 (split-beam) and 200kHz (dual-beam) frequencies. At each start of each experiment, the live fish are placed in the cage at the surface, then the cage is lowed to about $4{\cal}m$ depth where it remains during the measurements. To test the acoustic models, predictions of target strength based on swimbladder morphometries of 10 red seabream offish total length from $103{\cal}mm{\;}to{\;}349{\cal}mm$ ($3 <$TL/\lambda$ < 45)are compared with conventional target strength measurements on the same, shock-frozen immediately after caged experiments. X-ray was projected along dorsal aspect to know the morphological construction of swimbladder. and fish body. At high frequencies, Helmholtz-kirchhoff(HK) approximation would greatly enhance swimbladdered fish modeling. Sound scattering model [HK-ray approximation model] for comparison to experimental target strength data was used to model backscatter measurements from individual fish. The scattering data can be used in the inverse method along with multiple frequency sonar systems to investigate the adequacy of classification and identification of fish

• 한국수산과학회지
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• 제51권1호
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• pp.79-90
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• 2018

Fish ages are critical information in fish stock assessments because they are required for age-structure models such as virtual population analysis and stochastic catch-at-age models, whose outputs include recruitment strengths, a spawning stock size (abundance or biomass), and the projection of a fish population size in future. However, most countries other than the developed countries have not identified ages of fish caught by fisheries or surveys in a consistent manner for a long time (e.g.,>20 years). Instead, data about fish body sizes (e.g., lengths) have been well available because of ease of measurement. To infer age compositions of fish in a target group using fish length data, we intended to improve the length frequency analysis (LFA), which Schnute and Fournier had introduced in 1980. Our study was different in two ways from the Schnute and Fournier's method. First we calculated not only point estimates of age compositions but also the uncertainty in those estimates. Second, we modified LFA based on the von Bertalanffy growth model (vB-based model) to allow both individual-to-individual and cohort-to-cohort variability in estimates of parameters in the vB-based model. For illustration, we used data about lengths of Korean mackerel Scomber japonicas caught by purse-seine fisheries from 2000-2016.

• 한국발생생물학회지:발생과생식
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• 제22권4호
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• pp.369-378
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• 2018

We determined the morphologic characteristics (body weight and degree of abdomen inflation) of the red spotted grouper, Epinephelus akaara, mother fish producing healthy eggs. Experimental fish were chosen from fish reared in a sea cage. The fish were divided into four size groups by body weight: 400~600, 600~800, 800~1,000, and 1,000~1,200 g and four stages (I~IV) of the degree of abdomen inflation. After hormone treatment, we observed the amount of ovulation-induced eggs, and rates of buoyancy, fertilization, embryonic survival, and hatching. As a result, mother fish with a body weight of 600 g or more spawned, and the fertilization rate, embryonic survival rate, and hatching rate were high in the 800~1,000 g range, thus showing effective ovulation induction. As a result of dividing the degree of abdomen inflation based on the anal fin of the mother fish into I-IV stages and determining hormone treatment time, the GSI was $0.9{\pm}0.2%$ at stage I, $2.3{\pm}0.2%$ at stage II, $5.6{\pm0.2%$ at stage III, and $7.9{\pm}0.9%$ at stage IV. The flotation rate and hatching rate were highest at stage III, and the fertilization rate and embryonic survival rate were highest at stage IV. Therefore, in terms of egg quality, the amount of eggs collected per mother fish, maturation, and histology were different depending on the degree of abdomen inflation. At stage III, where the abdomen inflation degree of the mother fish was based on the basal part of the dorsal fin relative to the height of the anal fin was 1, the egg quality was highest.

• Fisheries and Aquatic Sciences
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• 제26권8호
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• pp.491-499
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• 2023

Lake Tinisu Abaya is home to some fish species. The lake's native fish species include Barbus and Tilapia zilli. Tilapia fish (Oreochromis niloticus L.) were stocked in Lake Tinishu Aabaya in 1997. This study aimed to investigate the feeding behaviors of O. niloticus in Lake Tinishu Abaya to develop an appropriate fisheries management approach in the lake. 428 O. niloticus fish samples (2.5 to 30.9 cm and 1.1 to 475 g) were collected to calculate the diet composition. Out of the total of 428 gut contents examined, 55 (12.85%) were found to be empty and 373 (87.15%) to be containing one or more food items. The diet behavior of the stocked fish in the study lake revealed that phytoplankton (39.5% by volume) and macrophytes (25.81% by volume) were the most noteworthy food items followed by detritus (14.39%) and zooplankton (12.95%). With increasing fish size, the importance of phytoplankton, macrophytes, and detritus increased while the contribution of zooplankton, insects, and other foods with an animal origin decreased. Seasonal variation in the diet composition of fish was evident (t-test; p < 0.05). Macrophytes, zooplankton, and detritus were the dominating food items during the wet season, while phytoplankton predominated during the dry season. This study demonstrated that O. niloticus had phytoplanktivores that primarily consumed phytoplankton and that the seasons and fish size had a significant impact on their feeding preferences. The diet of O. niloticus in Lake Tinishu Abaya comprised foods with both plant and animal origins. It concludes that the dietary habit of O. niloticus in the lake is, generally, the omnivorous type.

• 한국수산과학회지
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• 제44권3호
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• pp.284-289
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• 2011

The feeding habits of the blackthroat seaperch Doederleinia berycoides were studied using 650 specimens collected in the Southern Sea of Korea, from January to December, 2005. The size (standard length, SL) of the specimens ranged from 6.3 to 35.2 cm. D. berycoides is a piscivore that consumes mainly teleosts such as Engraulis japonicus, Acropoma japonicum, and Myctophum nitidulum. Of the fish species Engraulis japonicus was the preferred prey. D. berycoides also eats small quantities of shrimps, amphipods, euphausiids, mysids, and crabs. D. berycoides showed ontogenetic changes in its feeding habits. Smaller individuals (5-10 cm SL) fed mainly on shrimp. The proportion of shrimp decreased with increasing fish size, and this decrease paralleled the increased consumption of fish. Fish accounted for almost all of the stomach contents of individuals larger than 15 cm SL. Cluster analysis based on the percentage dry weight (%DW) identified two size groups: group A (<15 cm SL) consumed primarily shrimp and fish; and group B (15< cm SL) preyed exclusively on fish. There was little seasonal change in the diet of D. berycoides, but shrimp constituted 41.8% of the summer diet in %W.

• 한국어병학회지
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• 제36권2호
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• pp.379-388
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• 2023

본 연구는 수온 24℃에서 체중 0.6-786 g 범위의 참돔 52개체의 SMR을 측정한 후 점진적인 저산소 조건에 노출시켜서 S_crit를 측정하여 개체 크기에 따른 저산소 내성을 평가할 목적으로 실시하였다. SMR (mg O₂ kg^-1hr^-1)은 SMR=351.59·W^-0.195 (r²=0.934, p<0.001)의 관계식으로 표시할 수 있었고, 체중(W) 증가에 따라 감소하는 경향을 보여주었다. 참돔의 체중과 S_crit 사이에는 S_crit (%)=2.316·logW+17.805 (r²=0.682, p<0.001)의 회귀직선식으로 나타낼 수 있었고, 체중 0.6-786 g인 개체의 S_crit는 17.3-24.4% 범위에서 개체 크기가 클수록 증가하여 작은 개체가 저산소 내성이 높은 것으로 나타났다.

• 한국수산과학회지
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• 제52권3호
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• pp.247-255
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• 2019

This study was conducted to investigate the effects of extrusion pressure and particle size of feed ingredients on the growth performance and plasma hormone activity in juvenile olive flounder Paralichthys olivaceus. Experimental diets were prepared with extrusion pressure manipulated by screw speed [low pressure (LP), 885 rpm/min; high pressure (HP), 708 rpm/min] and different dietary particle sizes [specific surface area: small (SS), $169.9m^2/kg$; large (LS), $67.4m^2/kg$] in a two-level factorial design. Four experimental diets (LP+SS, LP+LS, HP+SS, and HP+LS) were randomly assigned to 12 tanks (3 replicates) stocked with 20 fish (initial weight, 57 g) per tank. After a 4-week feeding trial, the observable trends of the main effects of extrusion pressure and particle size on growth performance showed that LP and SS enhanced fish weight gain. The plasma insulin-like growth factor-I level was significantly higher in fish fed the LP+SS diet than in fish fed the HP+SS diet. These results indicate that manipulation of the physical qualities of feed through adjustment of extrusion pressure and feed ingredient particle size may influence the growth performance of juvenile olive flounder, which should be considered in feed manufacture.