• 생태와환경
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• 제34권4호통권96호
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• pp.310-318
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• 2001

낙동강에서 치어섭식이 동물플랑크톤에 미치는 영향을 채집된 치어의 소화관조사를 통해 고찰하였다. 조사지역인 낙동강 하류 물금에서는 유량이 감소하고 수체가 정체되는 5월에서 6월사이 5종류의 치어가 높은 밀도를 나타내었다 같은 시기, 동물플랑크톤 군집내에서는 대형윤충류인 Asplanchna spp.와 Brachionus spp., 지각류인 Moina micrura 및 Bosminopsis deitersi의 밀도가 큰 폭으로 감소하였다. 반면, Polyarthra속의 소형윤충류는 최대 밀도를 나타내었다. 채집된 치어의소화관 조사 결과, 15 mm이하의 치어는 대형윤충류 및 지각류를, 15mm 이상의 치어인 경우 지각류를 선택적으로 섭식하는 것으로 나타났다. 큰입배스의 치어의 경우, 같은 시기 채집된 치어에 비해 대형이었으며 동물플랑크톤 뿐 아니라 다른 치어를 포식하는 것으로 조사되었다. 조사 결과, 이시기의 낙동강 동물플랑크톤 군집내의 대형 윤충류와 지각류의 급격한 밀도 감소는 치어의 섭식으로 인한 것으로 사료된다. 반면, 이러한 밀도감소는 치어의 수가 감소함에 따라 회복되는 경향을 보였다. 부영양화된 낙동강의 경우 배스치어의 섭식으로 인한 치어밀도의 급속한 감소, 풍부한 먹이농도 등이 감소한 지각류의 밀도회복을 유도하는 것으로 사료된다.

• 수산해양기술연구
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• 제52권4호
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• pp.386-393
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• 2016

It is essential to provide good environment for juvenile fish to grow and spawn in order to keep reproduction mechanism of fisheries resources. However, harvesting juvenile fish deprives adult fish of the opportunity to reproduce, thereby changing self-regulating renewable resources into non-renewable ones and preventing sustainable harvesting as well as reducing fishers' income. We reviewed the catch status of Korea on juvenile mackerel and analyzed how reducing the catch ratio of juvenile mackerel may affect the spawning stock and Korean fishermen's revenue. In addition, we analyzed the problem of caching juvenile mackerel in Korean fisheries and current efforts to protect and reduce the catch ratio of juvenile mackerel in Korea. Furthermore, we suggested future efforts to protect juvenile mackerel. The result of the study showed that reducing the catch ratio of juvenile mackerel from 44.4% to 30.0% would increase fishers' revenue by 60.6 billion KRW. We suggest the changing of purse seine fishery's catching methods from night operation to day operation, relocation of fishing vessels to move to other fishing grounds when fishing vessels meet high density of juvenile mackerel, and consumers' clever choice of consuming adult mackerel in order to accelerate the move toward protecting juvenile mackerel in Korea.

• 한국수산과학회지
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• 제49권5호
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• pp.607-611
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• 2016

This study was conducted to investigate the effects of different water temperatures on growth, survival, biochemical composition, and blood physiological parameters of juvenile mandarin fish Siniperca scherzeri. Feed-trained juvenile fish were subjected to four water temperatures (20, 23, 26 and 29℃) with two replicate groups. The fish were fed to apparent satiation twice daily using a formulated diet containing 55% crude protein and 6% crude lipid. After the 8-week feeding trial, survival was >96% in all groups. Weight gain and feed efficiency of fish reared at 26 and 29℃ were higher than those reared at 20℃. The protein efficiency ratio, daily feed intake, and whole body proximate composition were not affected by water temperature. These results indicate that a suitable water temperature range for optimal growth and feed efficiency of juvenile mandarin fish is 26-29℃ under these experimental conditions.

• 한국수산과학회지
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• 제53권4호
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• pp.538-543
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• 2020

A feeding trial was conducted to investigate the effect of feeding frequency on the growth performance and body composition of juvenile mandarin fish Siniperca scherzeri. Triplicate groups of fish (initial fish weight, 7.5 g/fish) were fed to apparent satiation at one, two, three or four meals per day for 8 weeks. The results showed that weight gain of fish fed one meal per day was significantly (P<0.05) lower than those fish fed two, three or four meals per day. Feed efficiency of fish fed two meals per day was significantly (P<0.05) higher than other experimental groups. The plasma cholesterol content was significantly lower in fish fed one meal per day than those fed two, three or four meals per day. Consequently, we can conclude that feeding juvenile mandarin fish twice daily to apparent satiation is acceptable and sufficient to achieve good growth and feed efficiency, as fish performance was not remarkably enhanced when feeding increased from two to four times per day.

• 수산해양교육연구
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• 제27권2호
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• pp.390-398
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• 2015

A feeding experiment was conducted to determine the use of distillers dried grain (DDG) as a partial replacement for fish meal in the diet for juvenile rockfish, Sebastes schlegeli. Four iso-nitrogenous (50% crude protein) and iso-caloric (4.3 kcal/g) diets (designated as DDG0, DDG7, DDG14, and DDG21) were formulated to contain 0, 7, 14, and 21% DDG. Triplicate groups of juvenile rockfish (initial body weight, $10.2{\pm}0.2g$) were fed one of the experimental diets to visual satiety twice a day (09:00 and 17:00) for 8 weeks. At the end of the feeding trial, survival of rockfish was above 97% and not affected by dietary DDG levels (P>0.05). Weight gain, feed efficiency and daily feed intake of juvenile rockfish were significantly decreased with increase of dietary DDG levels (P<0.05). Condition factor, hepatosomatic index and visceralsomatic index of juvenile rockfish were not significantly affected by dietary DDG levels (P>0.05). No significant differences were observed in the contents of moisture, crude protein, crude lipid and ash of the whole body and dorsal muscle in juvenile rockfish fed the experimental diets (P>0.05). Therefore dietary inclusion of DDG as a replacement for fish meal could depress the growth of juvenile rockfish.

• Fisheries and Aquatic Sciences
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• 제12권4호
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• pp.305-310
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• 2009

This study was carried out to evaluate the use of fermented skipjack tuna viscera (FSTV) as an alternative for fish meal in juvenile olive flounder (Paralichthys olivaceus) diets. Lactobacillus bulgaricus was used as a starter for fermentation of skipjack tuna viscera. Four isonitrogenous (49% crude protein) and isocaloric (4 kcal/g DM) diets were formulated to contain graded levels (0, 5, 10, and 15%) of FSTV. Each experimental diet was fed three replicate groups (40 fish per tank) of juvenile flounder (average weight, $3.3\pm0.2$ g) for 5 weeks. At the end of feeding experiment, inclusion of FSTV up to 15% in diets did not affect survival rate (%) and weight gain of fish. Feed efficiency, protein efficiency ratio, protein and lipid retentions of fish fed the diet containing 10% FSTV were higher than those of fish fed the control diet (P<0.05). The values of fish fed the diet containing 15% FSTV were not different from those of fish fed other diets. Whole body lipid content of fish fed the diet containing 10% FSTV was higher than that of fish fed the diet containing 15% FSTV and control diet. The present results indicate that fermented skipjack tuna viscera could partially replace fish meal in juvenile flounder feed, and the inclusion of 10% FSTV may be efficient in improving the feed utilization of fish.

• 한국수산과학회지
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• 제45권2호
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• pp.132-138
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• 2012

An 8-week feeding experiment was conducted to evaluate three types of squid Sepia esculenta liver powder (SLP) as a dietary protein source replacing fish meal (FM) in juvenile olive flounder Paralichthys olivaceus. To replace FM, six experimental diets were formulated with three types (A, B, C) of SLP at the 5 and 10%: SLP-A5, SLP-A10, SLP-B5, SLP-B10, SLP-C5, and SLP-C10. One control diet contained 100% FM as the main protein source and another was a commercial diet (Com). Fish with an average body weight of $22.8{\pm}0.4$ g ($mean{\pm}SD$) were allocated randomly to aquaria in groups of 20 fish and fed the experimental diets in triplicate to satiation. The weight gain (WG) and specific growth rate (SGR) of fish fed the SLP-C10 diet were lower than those of fish fed the FM and SLP-B5 diets. No significant difference was observed in the WG and SGR among fish fed the diets other than SLP-C10. The feed efficiency (FE) and protein efficiency ratio (PER) of fish fed each SLP diet did not differ from those fed the control diet. However, fish fed SLP-C5 and SLP-C10 had a lower FE and PER than the fish fed commercial, SLP-A5 and SLP-B5 diets. Each SLP diet except for SLP-C10 could replace up to 10% of FM for juvenile olive flounder. The results of this experiment provide information that will assist in formulating an inexpensive practical diet containing SLP for juvenile olive flounder.

• 한국수산과학회지
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• 제49권3호
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• pp.317-322
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• 2016

This study was carried out to investigate the effects of various dietary lipid sources on the growth performance, body composition, and fatty acid profiles of juvenile fancy carp (Cyprinus carpio var. koi). Three replicate groups of fish (initial mean body weight, 15.1±0.18 g) were fed one of five experimental diets containing fish oil (SLO), soybean oil (SO), linseed oil (LO), lard (LA), or a mixture of SLO, SO, and LO (Mix) for 8 weeks. Fish fed the LA diet gained less weight than did fish fed the LO diet. The feed efficiency and protein efficiency ratio of fish fed the LA and Mix diets were lower than those of fish fed the SO and LO diets. The body lipid content of fish fed the SO diet was lower than those of the other groups. Whole-body fatty acid compositions reflected the fatty acid compositions of dietary lipid sources. Fish fed the SO diet had high concentrations of linoleic acid and arachidonic acid, whereas fish fed the LO diet were rich in linolenic acid. Fish fed the SLO diet had significantly higher levels of eicosapentaenoic acid and docosahexaenoic acid compared with fish fed the SO, LO, and LA diets. The results of this study suggest that SO or LO could be used as a replacement for SLO in the diets of juvenile fancy carp without any negative effects on growth and feed utilization when the dietary essential fatty acid requirements are satisfied for juvenile fancy carp.

• 한국수산과학회지
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• 제53권2호
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• pp.181-190
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• 2020

This study was conducted to estimate the optimum dietary DHA oil level and replacement level of enzyme treated fish meal (EFM) with sardine fish meal for juvenile Atlantic bluefin tuna Thunnus thynnus. Four diets were used: 1) EFM75 in which 75% EFM and 4% DHA oil were applied, 2) EFM60, with 60% EFM and 15% sardine fish meal, 3) DHA2 with 2% of DHA oil, and 4) SL as a raw fish feed. In a feeding trial, juvenile bluefin tuna (body weight 30.1 g) were randomly stocked into four experimental tanks (69 tones) and fed the experimental diets for 13 days. Fish weight gain was higher in the EFM75 and SL groups than in the DHA2 and EFM60 groups. The feed conversion ratio was lower in the EFM75 and DHA2 groups than in the EFM60 and SL groups. Survival was higher in fish fed the formulated diet groups (EFM75, EFM60 and DHA2) than in fish fed SL. This study clearly indicates that up to 10% dietary sardine fish meal can be used in juvenile T. thynnus diets, with an optimum dietary DHA oil level of approximately 3%.

• 한국양식학회지
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• 제20권1호
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• pp.56-59
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• 2007

Effect of dietary nutrient composition on growth and body composition of juvenile olive flounder Paralichthys olivaceus with different feeding strategy was determined. Twenty-five fish averaging 16 g were randomly distributed into 12, 180 L flow-through tank each. Four treatments in triplicates were prepared: fish were fed to satiation twice daily by the control diet for 8 weeks as the control group (Con) and fish were fed to satiation twice daily by the control and high nutrient diets for 6 weeks after 2-week fasting (2WS-6WFC, 2WS-6WFHN, respectively) and finally, fish were fed to satiation twice daily by the high nutrient diet for the consecutive 3 days after 4-day fasting for 8 weeks (4DS-3DFHN). No significant difference was found in either survival or weight gain of flounder among treatments. Feed efficiency ratio (FER) for fish in the 2WS-6WFHN treatment was significantly higher than that for fish in the Con and 2WS-6WFC treatments. Protein efficiency ratio (PER) of fish in the 2WS-6WFHN and 4DS-3DFHN treatments was significantly higher than that of fish in the 2WS-6WFC treatment. In conclusion, manipulation of dietary nutrient composition and/or feeding strategy can effectively improve growth of juvenile olive flounder without growth retardation at restricted feeding regime.