• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.2
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• pp.88-95
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• 2016

Most grid sorting has been used to sort out flatfish in shrimp fisheries, while double grid systems have been tested to separate smaller shrimp. The escape of juvenile red seabream through separating panels made with steel grids or large mesh tested for masking effects in a two-species system. Fish behavior was observed in a circulating water tank. The escape rate was 20% greater with the separating codends than with the normal codend in the single-species experiments. The rates in the two-species experiments were 30% or 20% greater than the single-species rates for the normal or separating codends, respectively. The seabream retention rates in the grid separator codend decreased as rockfish retention increased, possibly due to a threat effect. Conversely, the retention rate of both species increased concurrently in the net separator, possibly due to a masking effect. The escape rates of juvenile red seabream varied by compartment in the mesh separating codend. These results suggest that grid separating codends can be used in the field as towed fishing gear to reduce juvenile catch.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.5
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• pp.690-699
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• 2014

Three feeding trials were conducted to evaluate the effects of feeding rate and water temperature on growth and body composition of juvenile Korean rockfish, Sebastes schlegeli rearing at 3 different water temperatures. A total of 270 fish (each experiment) individual body weight (BW) averaging $16{\pm}0.3g$ ($mean{\pm}SD$) were fed a commercial diet for 4 wk at $16^{\circ}C$, $20^{\circ}C$, and $24^{\circ}C$. At each temperature, triplicate tanks were assigned to one of 6 feeding rates: 1.5%, 2.5%, 2.8%, 3.1%, 3.4%, and satiation (3.7% BW/d) at $16^{\circ}C$, 1.9%, 2.9%, 3.2%, 3.5%, 3.8% and satiation (4.1% BW/d) at $20^{\circ}C$ and 1.7%, 2.7%, 3.0%, 3.3%, 3.6%, and satiation (3.9% BW/d) at $24^{\circ}C$ water temperature. Weight gains of fish in satiation and 3.4% groups at $16^{\circ}C$, in satiation and 3.8% groups at $20^{\circ}C$ and in satiation and 3.6% groups at $24^{\circ}C$ were significantly higher than those of fish in the other treatments (p<0.05). A broken line regression analysis of weight gain indicated that optimum feeding rates of juvenile Korean rockfish were 3.41% at $16^{\circ}C$, 3.75% at $20^{\circ}C$ and 3.34% at $24^{\circ}C$ water temperature. Results of the present study indicate that the optimum feeding rate could be >3.1% but <3.41% at $16^{\circ}C$, >3.5% but <3.75% at $20^{\circ}C$ and >3.0% but <3.34% at $24^{\circ}C$. As we expected results suggest that fish performed better at $20^{\circ}C$ than $16^{\circ}C$ or $24^{\circ}C$ water temperature and the optimum feeding rate could be 3.1% BW/d to 3.7% BW/d in 16 g of juvenile Korean rockfish.

• Fisheries and Aquatic Sciences
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• v.13 no.1
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• pp.63-70
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• 2010

Two feeding experiments were conducted to investigate the effects of dietary genetically modified (GM) soya and com on growth performance, feed utilization and body composition of juvenile olive flounder, Paralichthys olivaceus and rockfish, Sebastes schlegelii. For each fish species, four isonitrogenous (50% crude protein) and isocaloric (4.1 kcal/g) diets (designated as nGM soya, GM soya, nGM com and GM com) were formulated to contain 20% non-GM (nGM) and GM soya and com. Thirty olive flounder (initial body weight, 15.4${\pm}$0.4 g) and fifty rockfish (initial body weight, 3.1${\pm}$0.02 g) were distributed in each 400 L tank (200 L water) in a flow through system. Each experimental diet was fed to triplicate groups of fish to visual satiation, twice a day (9:00 hand 17:00 h) for 6 weeks. Growth performance was measured every three weeks. No effects of GM feedstuffs on survival were observed. Dietary inclusion of GM feedstuffs did not affect growth performance and feed utilization of fishes, except for rockfish fed GM com. Rockfish fed the GM com diet showed higher weight gain, daily feed intake and daily protein intake than did fish fed the nGM com diet, but no significant differences were observed in final body weight between the dietary treatments. Condition factor, hepatosomatic index, visceral somatic index and body composition were not altered by the inclusion of GM feedstuffs. These results indicate that dietary inclusion of GM soya and com could have no effects on growth performance and feed utilization of juvenile flounder and rockfish. Lower weight gain and feed intake in flounder and rockfish fed the diets containing 20% soya were likely due to anti-nutritional factors, rather than transgenic factors in the feedstuffs. Dietary inclusion of GM soya and com at the level tested did not alter the body composition of fishes. Further studies to investigate the effects of GM feedstuffs on health conditions and the development of fishes, as well as those of residue of transgenic fragments in ambient environments and in animals are necessary for safe use of the ingredients in aquaculture.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.5
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• pp.683-688
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• 2016

The effects of dietary supplementing natural additives [yacon (YC), ginger (GG), and blueberry (BB)] on growth, feed utilization, and body composition of juvenile rockfish were compared to those of ethoxyquin (EQ), which is commonly used to prevent rancidity of fish feed. A total of 480 fish were distributed randomly into 12 50-L flow-through tanks (40 fish/tank). Four experimental diets were prepared: the control diet (Con) with 0.01% EQ, and the YC, GG and BB diets containing 1% YC, GG, and BB instead of wheat flour. Each diet was assigned randomly to triplicate tanks of fish, which were hand fed to satiation twice daily for 8 weeks. Weight gain of fish fed the YC diet was higher than that of fish fed all other diets. Feed efficiency (FE), protein efficiency ratio (PER), and protein retention (PR) in fish fed the YC diet were higher than those in fish fed the other diets. Whole-body chemical composition of the fish was affected by the additive sources. In conclusion, dietary supplementation with GG effectively improved weight gain and feed utilization (FE, PER, and PR) of juvenile rockfish.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.6
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• pp.823-829
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• 2016

Yacon (YC), ginger (GG) and blueberry (BB) were added to the diet of juvenile rockfish Sebastes schlegeli to investigate the effects of these substances on growth, feed utilization and resistance to Streptococcus iniae compared to feed additive ethoxyquin. A total of 480 fish were distributed in 12 tanks and four experimental diets [control (Con), with 0.01% ethoxyquin, and 1% YC, GG and BB diets] were provided in triplicate. After an 8-week feeding trial, 20 fish from each tank were infected with Streptococcus iniae. Fish fed the BB diet had higher weight gain than fish fed the GG and Con diets. Feed efficiency of fish fed the GG and YC diets was higher than that of fish fed the BB and Con diets. The protein efficiency ratio of fish fed the GG diet was higher than that of fish fed any other diet. The cumulative mortality 54 h after infection of fish fed the Con diet was higher than that of fish fed any other diet. These results indicate that YC, GG, and BB are effective dietary additive, not only improving growth performance and feed utilization but also lowering the mortality of juvenile rockfish exposed to S. iniae.

• Fisheries and Aquatic Sciences
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• v.13 no.2
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• pp.118-126
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• 2010

A feeding trial was conducted to investigate the effects of different levels of dietary n-3 highly unsaturated fatty acids (HUFA) (1.1-5.6%) and vitamin E (70 and 400 mg/kg) on the growth and body composition of juvenile rockfish. Six isonitrogenous (45% crude protein) and isolipidic (17% crude lipid) diets were formulated to contain graded levels of n-3 HUFA and vitamin E. Diets 1, 2 and 3 consist of 400 mg vitamin E/kg diet with graded levels of 1.1, 3.0, and 5.6% n-3 HUFA, respectively. Graded levels of n-3 HUFA (1.1, 3.0, and 4.0%) were added in diets 4, 5 and 6, respectively, containing 70 mg vitamin E/kg diet each. At the end of feeding trial, growth performance of rockfish was affected by neither dietary n-3 HUFA nor vitamin E levels. Feed efficiency and hepatosomatic index were slightly decreased (P<0.05) with increment of dietary n-3 HUFA at each dietary vitamin E level. Dietary vitamin E and n-3 HUFA levels did not affect proximate composition and vitamin E concentration in the dorsal muscle of rockfish. Liver moisture and crude protein contents positively related to dietary n-3 HUFA levels. Liver lipid content and hematocrit value were significantly decreased (P<0.05) by increasing dietary n-3 HUFA levels. Eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3; DHA) concentrations in the dorsal muscle significantly correlated to dietary n-3 HUFA levels, except for fish fed the diet 6 containing 4% n-3 HUFA and 70 mg vitamin E/kg diet. EPA concentration in the dorsal muscle of fish fed the diet 6 was significantly lower than that of fish fed the diets 2, 3 and 5. The present findings suggest that feeding of diets containing excessive n-3 HUFA level with varying addition of vitamin E may alter fatty acid composition in the dorsal muscle, but do not affect growth of juvenile rockfish.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.4
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• pp.412-420
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• 1995

Oxygen consumption (OC), ammonia nitrogen (AN ) excretion and body composition were measured to study the effects of energy/protein ratio (EPR) on the utilization of protein and energy in juvenile rockfish, Sebastes schiegeli. Juvenile rockfish were divided into three groups that they fed three isocaloric diets (3,5kcal/g) containing 30 (I), 40 (II) or $50\%$ crude protein (III). EPR of the three experimental diets were 11.5 (I), 8.7 (II) and 7.0kcal/g III), respectively. Juvenile rockfish (wet wt. 2.9-3.1g) were cultured in 501 aquaria with the constant environmental condition of $20-24^{\circ}C$ water temperature and $34\%o$ salinity. For 24 hr after feeding the diets, juvenile rockfish fed diet III had a higher OC than did the fish from groups fed diets I and II, and average OC of the fish fed diets I, II and III were $0,93\pm0.02^a,\;0.92\pm0.02^a\;and\;1.03\pm0.03^bml\;O_2/g/h$, respectively. AN responses of juvenile rockfish to increasing levels of dietary protein (decreasing dietary EPR) were significantly different among three groups in which dietary protein at elevated levels increased the excretion of AN for 24 hr after feeding the diets. Average AN excretion of the fish fed diets I, II and III were $9.14\pm0.39^a,\;12.41\pm 0.53^a\;and\;14.89\pm0.55^c\;{\mu}g\;N/g/h$ respectively. The body protein content of the fish fed diet II for 59 days was significantly higher than that of the fish fed the other diets. But, there were no significant differences between three groups in body lipid, carbohydrate and ash contents. These results indicate that EPR of 9.7kcal/g (diet II) could be a optimum EPR in juvenile rockfish diet.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.6
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• pp.746-752
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• 2013

An 8-week feeding experiment was conducted to evaluate three types of squid Sepia esculenta liver powder (SLP) as a dietary protein source for replacement of fish meal (FM) in the juvenile black rockfish, Sebastes schlegeli. For replacement of FM, six experimental diets were formulated with 5 or 10% of either of three types (A, B, C) of SLP: SLP-$A_5$, SLP-$A_{10}$, SLP-$B_5$, SLP-$B_{10}$, SLP-$C_5$, and SLP-$C_{10}$. One of the control diets contained 100% FM as the protein source, and the other was a commercial diet (Com). Fish with an average body weight of $6.50{\pm}0.03g$ ($mean{\pm}SD$) were allocated randomly in triplicate groups of 50 to aquaria and fed the experimental diets until satiation. The weight gain (WG) and specific growth rate (SGR) of fish fed the FM, SLP-$A_5$, SLP-$A_{10}$, and SLP-$B_5$ diets were higher than those of fish fed the Com, SLP-$B_{10}$, SLP-$C_5$ and SLP-$C_{10}$ diets. No significant differences were observed in WG and SGR among the diet groups, with the exception of the SLP-$C_{10}$ diet group. The feed efficiency (FE) and protein efficiency ratio (PER) of fish fed the SLP-$A_5$, SLP-$A_{10}$, and SLP-$B_5$ diets did not differ from those fed the control diet. However, fish fed SLP-$B_{10}$ and SLP-$C_{10}$ had lower FE and PER than the fish fed the FM, commercial, SLP-$A_5$, SLP-$A_{10}$, and SLP-$B_5$ diets. Both the SLP-A and SLP-B diets, but not the SLP-C diets, replaced up to 10% and 5% of FM for juvenile black rockfish, respectively. The results of this experiment provide information that will assist in formulating an inexpensive and practical diet containing SLP for juvenile black rockfish.

• Korean Journal of Ichthyology
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• v.10 no.1
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• pp.106-114
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• 1998

In order to estimate energy budget of the rockfish, Sebastes schlegeli juvenile, during the period from parturition to juvenile, of rockfish were reared at constant condition of water temperature($16^{\circ}C$ and $20^{\circ}C$). Energy used by the reared juveniles were calculated from estimates of data on growth, oxygen consumption, nitrogen excretion, feeding and energy content. After parturition, total length of juvenile was 4.56~5.49mm(average 4.97mm, n=20), and the average dally growth rates were 0.50mm at $20^{\circ}C$. The weight-specific oxygen consumption and nitrogen excretion rates decreased with increasing body weight. Temperature significantly affected oxygen consumption and nitrogen execretion rates, with the higher rates at $20^{\circ}C$ than $16^{\circ}C$. During the 25 days from parturition to jllveniles, feeding rates were 65.8cal at $16^{\circ}C$, and 89.2cal at $20^{\circ}C$. The assimilation effeciency estimated by nitrogen content of food and egested feces were 85.21% at $16^{\circ}C$ and $20^{\circ}C$. During the period from parturition to juvenile, energy was used the higher in body growth than in oxygen consumption. The gross growth efficiencies($K_1$)and net growth efficiencies($K_2$) of the rockfish, Sebastes schlegeli juvenile ranged from 43% to 47% and from 50% to 55%, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.3
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• pp.323-329
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• 2016

The effects of dietary antioxidant [saltwort (SW), leek (LK), and dandelion (DD)] supplementation on the growth, body composition, serum chemistry, and challenge test results of juvenile rockfish, Sebastes schlegelii, were determined. In an experiment, 320 fish were randomly distributed into eight, 50-L flow-through tanks (40 fish per tank). Four experimental diets were prepared: the control diet (Con) with synthetic antioxidant: and diets with SW, LK, or DD from natural sources. Each diet was randomly assigned to duplicate tanks of fish, which were hand-fed to satiation twice daily for 8 weeks. After the 8-week feeding trial, 20 fish from each tank were artificially infected with Streptococcus iniae and monitored for 6 days. The dietary additives did not affect survival, weight gain, specific growth rate, feed efficiency (FE), protein efficiency ratio (PER), or plasma chemistry. However, the cumulative mortality of fish fed the SW, LK and DD diets was lower than that of fish fed the control diet beginning 4 days after infection. In conclusion, dietary supplementation with SW, LK, and DD did not affect the growth, FE, PER, or plasma chemistry of rockfish. However, dietary inclusion of SW, LK, and DD lowered the mortality of rockfish following infection with S. iniae.