Effects of Light Intensity and Salinity on Growth, Survival, and Whole-Body Osmolality of Larval Southern Flounder Paralichthys lethostigma

The southern flounder Paralichthys lethosligma is a high‐valued flatfish found in estuarine and shelf waters of the south Atlantic and Gulf coasts of the United States. Wide temperature and salinity tolerances exhibited by juveniles and adults make it a versatile new candidate for commercial culture, and studies are underway in the southeastern U.S. to develop hatchery methods for this species. The objectives of this study were to establish illumination and salinity conditions that optimize growth and survival of larval southern flounder reared through the yolk‐sac and first feeding stages to 15‐d post‐hatching (15 dph). Early embryos were stocked into black 15‐L tanks under light intensities of 5, 50, 100, and 1,000 Ix and at salinities of 24 and 34 ppt in a 4 ± 2 factorial design. Significant (P 0.05) effects of both light intensity and salinity on growth and survival were obtained, with no interaction between these effects. On 11 dph and 15 dph, growth was generally maximized at the intermediate light intensities (50 and 100 Ix) and minimized at the extremes (5 and 1,000 Ix). By 15 dph, growth was higher at 34 ppt than at 24 ppt. Survival to 15 dph showed trends similar to those of growth. Survival was higher at 100 Ix (avg. = 46%, range = 41–54%) than at 5 Ix (avg. = 11%, range = 6–17%) and higher at 34 ppt (avg. = 43%, range = 3145%) than at 24 ppt (avg. = 17%, range = 8–38%). Whole‐body osmolality (mOsmol/kg) was significantly lower in larvae reared at 24 ppt (avg. = 304, range = 285–325) through 11 dph than in larvae reared at 34 ppt (avg. = 343, range = 296–405). Larvae reared under the extreme light intensity treatments (5 and 1,000 Ix) at 34 ppt appeared to exhibit osmoregulatory stress, particularly on 11 dph, when a marked increase in whole‐body osmolality was observed. The mid‐intensity treatments (50 and 100 Ix) at 34 ppt optimized growth and survival of larval southern flounder in this study; and elicited the most stable osmotic response. These conditions appear to be consistent with those that southern flounder larvae encounter in nature during this early developmental period.     

Effect of stocking density and feeding regime on larval growth,survival, and larval development of Japanese flounder,Paralichthys olivaceus,using live feeds

This research examined the effect of initial stocking density and feeding regime on larval growth and survival of Japanese flounder, Paralichthys olivaceus. Larval rearing trials were conducted in nine 50‐L tanks with different initial stocking densities combined with different feed rations (20 larvae/L with standard feed ration [LD], 80 larvae/L with standard feed ration [HD], and 80 larvae/L with four times the standard feed ration [HD+]). Larvae were stocked on 0 days posthatch (DPH) following hatching of the fertilized embryos. Larval total length (TL), survival rates, and final densities were observed on larval settlement (32 DPH) to evaluate larval rearing performance. At 32 DPH, there were no significant differences (p > .05) in TL or survival rates between the LD (46.5 ± 17.0%) and HD+ (40.3 ± 9.4%). The TL and survival rate of HD (23.1 ± 3.5%) were significantly lower than that of LD and HD+ (p < .05). However, the larval density of HD was significantly higher than that of LD (p < .05). HD+ achieved the best larvae production (32.27 ± 7.51 larvae/L), supported by sufficient food source, high water exchange, and proper water quality management (routine siphoning, surface skimming). The larval‐rearing protocols and larval development from hatching to metamorphosis is described in detail, with corresponding photographs taken during the experiment.     

Interactive effects of dietary leucine and isoleucine on growth,blood parameters,and amino acid profile of Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

A 60-day feeding trial was conducted to assess the interactions of dietary leucine (Leu) and isoleucine (Ile) on Japanese flounder. Fish of 2.69 ± 0.04 g were fed experimental diets containing two levels of Leu (2.58 and 5.08% of diet) combined with three levels of Ile (1.44, 2.21, and 4.44% of diet), respectively. After the feeding trial, growth, proximate composition, muscle total amino acid profile, blood parameters, mucus lysozyme activity, and stress tolerance to freshwater were measured. Statistically significant (P < 0.05) interactive effects of Leu and Ile were found on growth parameters (final body weight, body weight gain, and special growth rate) of Japanese flounder. Antagonism was discovered in high dietary Leu groups, while stimulatory effects were obtained for increased dietary Ile in low Leu groups. Interactive effects of these two branched-chain amino acids were also found on hepatosomatic index of test fish. In addition, crude lipid content of fish whole body was significantly altered by various diets, with antagonism observed in low dietary Leu groups. Interactive effects also existed in muscle amino acid profiles for low fish meal diets, but no interactive impacts were observed on blood parameters. Furthermore, lysozyme activities and freshwater stress were significantly affected by different diets. And antagonism was found on lysozyme activities in low Leu groups. Moreover, high Leu and high Ile levels of diet significantly altered freshwater stress tolerance of Japanese flounder. These findings suggested that dietary Leu and Ile can effect interactively, and fish fed with diets containing 2.58% Leu with 4.44% Ile and 5.08% Leu with 1.44% Ile showed better growth performance.     

Optimum dietary protein to lipid ratio for Starry flounder (Platichthys stellatus)

An 8‐week feeding trial was conducted to evaluate the optimum dietary protein to lipid ratio (P/L) for Starry flounder Platichthys stellatus (30.7 ± 0.7 g initial weight). Nine fishmeal‐based diets with three protein levels (40%, 45% and 50%) and three lipid levels (8%, 11% and 14%) were fed to 30 fish in triplicate. Results showed that the growth performance was affected by dietary P/L ratio significantly, and the best weight gain rate, specific growth rate and feed conversion ratio were appeared at fish fed P45L14 and P50L11 diets. Apparent digestibility coefficient of protein was increased with increasing dietary lipid, but lipid digestibility was decreased by dietary lipid. Lipid deposition in tissues was increased with increasing dietary lipid at each protein level and was higher for the lower protein diets. In liver, the per cent of both eicosapentaenoic acid and docosahexaenoic acid were increased by dietary protein. High dietary protein level (50%) at high lipid level (14%) increased arachidonic acid significantly. Aspartate aminotransferase and alanine aminotransferase were affected significantly by dietary P/L ratios. High density lipoprotein cholesterol and total cholesterol of 45% protein groups were significantly higher than others. The study revealed that the optimum dietary protein to lipid ratio for starry flounder was P45L14 or P50L11, or P/E ratios were 25.49 and 27.70 mg protein kJ^?1 gross energy respectively.     

Effect of prey type and size on the growth,survival and pigmentation of cod (Gadus morhua L.) larvae

The aim of this study was to investigate the effect of natural zooplankton versus rotifers and the effect of prey size on the growth and survival of cod larvae. At 20 days post hatch (DPH) myotome height, standard length and dry mass were significantly higher in larvae fed zooplankton compared to those fed rotifers. The dry mass at age 25 DPH was 135 μg (±45), 331 μg (±114), 391 μg (±121) for larvae fed rotifers, small size and large size plankton, respectively. At 25 days post hatch, the survival rates were 41.8% (±10.5), 90.7% (±2.3) and 91.4% (±1.7) for larvae reared on rotifers, small size and large size plankton, respectively. The limited growth and survival of cod larvae reared on rotifers were not mainly caused by the small size of rotifers. Large differences in skin coloration between larvae in the rotifer group and the two zooplankton groups were observed, probably caused by the large difference in astaxanthin levels in rotifers and natural zooplankton. We suggest that the nutritional composition of rotifers is a limiting factor for cod larvae growth and survival.     

Effects of soy protein ratio,lipid content and minimum level of krill meal in plant‐based diets over the growth and digestibility of the white shrimp,Litopenaeus vannamei

This study evaluated the effects of soy protein ratio, lipid content and the minimum dietary level of krill meal in plant‐based diets over the growth performance and digestibility of Litopenaeus vannamei. Nine plant‐based diets varied the soybean meal (SBM) and soy protein concentrate (SPC) inclusion ratio at 1 : 2.3, 1 : 1 and 2.5 : 1, and their dietary lipid content at 121.4 ± 9.4, 102.3 ± 1.2, and 79.9 ± 1.2 g kg^?1 (in a dry matter basis). An additional diet containing 120 g kg^?1 of fish meal (salmon by‐product) was used as a control. Krill meal was included at 0, 5, 10, 20 and 30 g kg^?1 in a new set of plant‐based diets. After 10 weeks in clear‐water tanks of 0.5 m³, no effect of SBM:SPC ratio and dietary lipid content was detected on shrimp survival. However, dietary lipid levels of 80 and 121 g kg^?1 combined with a high SPC to SBM resulted in the lowest final body weight and the poorest apparent crude protein digestibility, respectively. Krill meal increased feed intake at only 10 g kg^?1, while at 20 g kg^?1, it accelerated shrimp growth, increased yield and reduced food conversion ratio.     

Growth and nutrient utilization of Murray cod Maccullochella peelii peelii (Mitchell) fingerlings fed diets with varying levels of soybean meal and blood meal

Abstract The Australian native freshwater fish Murray cod, Maccullochella peelii pellii (Mitchell), currently supports a fledgling inland aquaculture industry, which is thought to have considerable growth potential. The aim of this study was to evaluate the suitability of two alternate protein sources [blood meal (BM) and defatted soybean meal (SBM)] as substitutes for fish meal at various levels of inclusion in diets for juvenile Murray cod. The growth performance of juvenile Murray cod in response to nine isonitrogenous and isocalorific diets (50% protein, 14% lipid, 20.2 kJ g^?1) consisting of a control diet in which protein was supplied from fish meal, and test diets in which the fish meal protein was substituted at levels of 8%, 16%, 24%, and 32% with BM or SBM was evaluated from a 70‐day growth experiment. The per cent apparent dry matter (% ADC_dm) and percentage protein digestibility (% ADC_p) of the test diets were also determined using Cr₂O₃ as a marker. Survival in all the SBM dietary treatments was high but that of fish on the BM dietary treatments was significantly (P < 0.05) lower than in all the other dietary treatments. Specific growth rate (% day^?1) of Murray cod fed SBM incorporated diets ranged from 1.63 ±  0.06 to 1.78 ±  0.10 and even at the highest level tested (32% of the dietary protein from SBM) was not significantly different (P > 0.05) from the fish fed the control diet (1.65 ±  0.09). Feed conversion ratios of the SBM dietary treatments ranged from 1.36 ±  0.08 to 1.45 ±  0.07. The protein efficiency ratios and protein conversion efficiencies of Murray cod in the soybean meal treatments were also good and for a majority of the SBM diets were better than those for the control diet. Per cent ADC_dm and ADC_p of the SBM diets tested ranged from 70.6 ±  1.46 to 72.3 ±  1.81% and 88.6 ±  0.57 to 90.3 ±  0.17%, respectively, and was not significantly different (P > 0.05) from the control diet (% ADC_dm 74.3 ±  1.63; % ADC_p 91.3 ±  0.55). The reasons for significantly poor survival and growth of Murray cod reared on BM incorporated diets, and relatively poor digestibility of these diets are discussed. The study shows that for Murray cod diets in which fish meal protein is substituted up to 32% performance or carcass composition is not compromised.     

Dietary supplemental effects of red seaweed Eucheuma denticulatum on growth performance,carcass composition and blood chemistry of juvenile Japanese flounder,Paralichthys olivaceus

A 56‐day feeding trial was conducted to determine the effects of supplementing diets of juvenile Japanese flounder, Paralichthys olivaceus, with Eucheuma denticulatum (EDP). Isonitrogenous and isolipidic test diets were prepared using a fishmeal‐based positive control diet (PC) and a fishmeal‐soy protein concentrate negative control diet (NC) supplemented with 3 (D3%), 6 (D6%) and 9% (D9%) EDP. The test diets were assigned to tanks (12 fish tank^?1, initial mean body weight of 0.42 ± 0.01 g) in triplicates. Results of the feeding trial indicated that growth rates and feed efficiency significantly improved (P < 0.05) when 3% EDP was supplemented in the diets. However, there was a significant reduction (P < 0.05) of growth and feed efficiency in fish fed diets with higher supplementation levels. Protein, lipid, dry matter and ash contents of carcass and their corresponding nutrient retention values were not markedly altered in all dietary treatments. Fish fed diets supplemented with EDP exhibited higher (P < 0.05) omega‐3 polyunsaturated fatty acid accumulation in dorsal muscle when compared with those of fish fed NC. Blood chemical parameters showed significant differences (P < 0.05) in total cholesterol and triglyceride levels. These results suggest that EDP can be efficiently utilized by Japanese flounder and can promote best growth and feed utilization at a level of 3%.     

Cryopreservation of summer flounder,Paralichthys dentatus L., sperm

The summer flounder, Paralichthys dentatus L., is a high‐value species and considerable research has been conducted to determine practices conducive for its culture. As milt can be limited in this species, experiments were conducted to develop a practical sperm cryopreservation protocol for hatchery use. Two dilution ratios (1:2 and 1:4; sperm:extender), 2 diluents (saline and sucrose‐based), 2 cryoprotectants (10% DMSO and 12% glycerol) and 3 freezing rates (?5, ?10 and ?15°C min^?1) were evaluated using differential staining to assess post‐thaw sperm survival. Seven combinations of the factors examined reduced post‐thaw viability by less than 30%. The average viability of sperm from fresh, pooled flounder milt (67.2 ± 2.9%) was not different from that of thawed milt diluted 1:4 with sucrose diluent (10% DMSO) frozen at ?5°C min^?1 (38.4 ± 7.7%) and fertilization and hatch success were not different in trials using fresh or thawed, cryopreserved sperm. From these experiments a practical sperm cryopreservation method was developed, but further refinement of the freezing protocol is necessary to optimize results.     

Synergistic effects of dietary vitamin E and selenomethionine on growth performance and tissue methylmercury accumulation on mercury‐induced toxicity in juvenile olive flounder,Paralichthys olivaceus (Temminck et Schlegel)

An 8‐week feeding trial was conducted to evaluate the synergistic effects of dietary vitamin E and selenomethionine (SeMet) on induced methylmercury (MeHg) toxicity in juvenile olive flounder Paralichthys olivaceus. Nine semi‐purified diets were formulated to contain three different vitamin E levels as DL‐α‐tocopheryl acetate (0, 100 and 200 mg TAkg^?1 diet) and three different selenium (Se) levels (0, 2 and 4 SeMet mg kg^?1 diet) on the constant mercury toxicity level (20 mg MeHgkg^?1 diet). Nine experimental diets, in a 3² factorial design (E₀Se₀, E₀Se₂, E₀Se₄, E₁₀₀Se₀, E₁₀₀Se₂, E₁₀₀Se₄, E₂₀₀Se₀, E₂₀₀Se₂ and E₂₀₀Se₄), were fed to triplicate groups of fish averaging 2.3 ± 0.04 g (mean ± SD) in the semi‐recirculation system. After 8 weeks of feeding trial, vitamin E and Se showed significant effects on weight gain (WG) of fish (P < 0.05). We found that there was a clear trend of increasing WG with elevating vitamin E and Se levels in the diets. Feed efficiency (FE), specific growth rate (SGR), protein efficiency ratio (PER) and survivability exhibited a similar trend with WG. Both antioxidants had significant interaction effects on FE and PER (P < 0.05). Methylmercury concentrations in fish muscle, liver and kidney decreases in a dose‐dependent manner as dietary vitamin E and Se levels increase. Interestingly, the most significant interactive effects of vitamin E and Se were found in liver tissue for depleting Hg concentrations (P < 0.05). These findings suggest that dietary vitamin E more than 100 mg TA kg^?1 diet with 2 or 4 mg SeMet kg^?1‐supplemented diets could have synergistic effects on growth and liver mercury bioaccumulation on MeHg‐induced toxicity in juvenile olive flounder.     

Optimum feeding rates in juvenile olive flounder,Paralichthys olivaceus,at the optimum rearing temperature

Two feeding trials were carried out to determine the optimum feeding rates in juvenile olive flounder, Paralichthys olivaceus, at the optimum rearing temperature. Fish averaging 5.0 ± 0.11 g (mean ± SD) in experiment 1 and 20.2 ± 0.54 g (mean ± SD) in experiment 2 were fed a commercial diet at the feeding rates of 0%, 3.0%, 4.0%, 4.25%, 4.5% and 4.75% body weight (BW) day^?1 and satiation (5.52% BW day^?1) in experiment 1 and 0%, 1.0%, 2.0%, 3.0% and 3.5% BW day^?1 and satiation (4.12% BW day^?1) in experiment 2 at 20 ± 1 °C. Both feeding trials lasted for 2 weeks. Results from experiment 1 indicated that weight gain (WG) and specific growth rate (SGR) of fish fed to satiation were significantly higher than those of fish fed at other feeding rates while feed efficiency (FE) and protein efficiency ratio (PER) of fish fed at 4.25% BW day^?1 were significantly higher than those of fish fed to satiation and fish fed at 3.0% BW day^?1 (P < 0.05). In experiment 2 WG, SGR and PER leveled out after the feeding rate of 3.5% BW day^?1 whereas FE reached a plateau at 3.0% BW day^?1. anova of FE indicated that the optimum feeding rates in 5.0 and 20 g juvenile olive flounder could be 4.25% and 3.0% BW day^?1, respectively. Broken line analysis of WG suggested the optimum feeding rates of 5.17% and 3.47% BW day^?1 in 5.0 and 20 g fish, respectively. Therefore, these results indicated that the optimum feeding rates could be >4.25 but <5.17% BW day^?1 for 5.0 g, and it could be >3.0 but <3.47% BW day^?1 for 20 g size of juvenile olive flounder at the optimum rearing temperature.     

Optimum dietary protein level for maximum growth of juvenile olive flounder Paralichthys olivaceus (Temminck et Schlegel)

This experiment was conducted to determine the optimum dietary protein level for juvenile olive flounder Paralichthys olivaceus (Temminck et Schlegel) fed a white fish meal and casein‐based diets for 8 weeks. Olive flounder with an initial body weight of 4.1 ± 0.02 g (mean ± SD) were fed one of the six isocaloric diets containing 35%, 45%, 50%, 55% and 65% crude protein (CP) at a feeding rate of 4–5% of wet body weight on a dry‐matter basis to triplicate groups of 20 fish per aquarium. After 8 weeks of feeding, per cent weight gain (WG) and feed efficiency ratios of fish fed the 55% CP diet were not significantly higher than those from fish fed the 50% and 65% CP diets, but significantly higher than those from fish fed the 35% and 45% CP diets. Fish fed the 50%, 55% and 65% CP diets had significant higher specific growth rates than did fish fed the 35% and 45% CP diets; however, there was no significant difference among fish fed the 50%, 55% and 65% CP diets. The protein efficiency ratio was inversely related to the dietary protein level; that is, maximum efficiency occurred at the lowest dietary protein level. Broken‐line model analysis indicated that the optimum dietary protein level was 51.2 ± 1.8% for maximum weight gain in juvenile olive flounder. The second‐order polynomial regression analysis showed that the maximum WG occurred at 57.7% and it revealed that the minimum range of protein requirement was between 44.2% and 46.4%. These findings suggest that the optimum dietary protein level for maximum growth could be greater than 46.4%, but less than 51.2% CP in fish meal and casein‐based diets containing 17.0 kJ g^?1 energy for juvenile olive flounder.     

The effect of dietary chitin on growth and nutrient digestibility in farmed Atlantic cod,Atlantic salmon and Atlantic halibut

The effect of adding 0%, 1%, 2% and 5% chitin from prawn shells in the diets for Atlantic cod, Atlantic halibut and Atlantic salmon on growth was investigated. Nutrient digestibility and feed utilization was investigated in salmon and cod. Atlantic cod grew from 186 ± 29 to 383 ± 78 g (N = 960) over 13 weeks. Dietary chitin had no effect on length, weight, condition, liver size or specific growth rate (SGR). The apparent digestibility (ADC) for protein ranged from 84.7% to 86.5%, lipid between 88.8% and 93.1% and dry matter from 96.1% to 96.6%. Feed utilization varied between 1.08 and 1.11 and was not correlated with dietary chitin content. Atlantic salmon tripled their weight from 199 ± 9 to 615 ± 75 g (N = 480) during the 13 weeks. High inclusions of chitin (>1%) reduced both growth rate and condition. Protein and lipid ADC was negatively correlated with dietary chitin. Feed utilization ranged between 0.86 and 0.90 and was not significantly affected by dietary chitin. Faecal protein increased significantly with increasing dietary chitin, while faecal dry matter and lipid did not. Individually tagged Atlantic halibut grew from 1300 ± 470 to 2061 ± 714 g (N = 70) during 6 months. Individual growth rates varied within each group from being slightly negative to 0.81%·day^?1. Diet had no significant effect on growth rates. Atlantic cod and Atlantic halibut seems unaffected by up to 5% chitin additions in the diet, while chitin >1% of diet negatively affects growth and nutrient utilization in Atlantic salmon.     

Effect of low molecular weight fish protein hydrolysate on growth performance and IGF‐I expression in Japanese flounder (Paralichthys olivaceus) fed high plant protein diets

Seven isonitrogenous and isoenergetic experimental diets were formulated to investigate the effect of low molecular weight fish protein hydrolysate (FPH) in diets on growth performance, feed utilization and liver IGF‐I mRNA levels in Japanese flounder (38.80 ± 1.11 g) fed with high plant protein diets. Fish meal protein was, respectively, replaced by 6% (FPH6), 11% (FPH11), 16% (FPH16), 21% (FPH21), 26% (FPH26) FPH of total dietary protein. FPH diets contained a constant high level of plant protein (690 g kg^?1) from soybean meal. As a positive control diet, FM2 contained about 590 g kg^?1 plant protein and 410 g kg^?1 fish meal protein, while negative control diet FM1 contained about 690 g kg^?1 plant protein and 310 g kg^?1 fish meal protein. The expression levels of liver IGF‐I mRNA were evaluated using real‐time PCR normalized against the 18S rRNA gene. The results showed that moderate low molecular weight FPH (FPH11) improved growth performance and protein retention. Fish fed with FPH11 and control diet FM2 had similar growth and feed utilization, while high‐level low molecular weight FPH did not improve growth performance and protein retention, and depressed liver IGF‐I mRNA expression in Japanese flounder.     

Influence of lipid level and supplemental lecithin in diet on growth,feed utilization and body composition of juvenile flounder (Paralichthys olivaceus) in suboptimal water temperatures

This study was conducted to investigate the influence of dietary lipid level and supplemental soy lecithin on growth, feed utilization and body composition of juvenile flounder reared at two suboptimal water temperatures, 12 and 17 °C. Three isonitrogenous (CP 50%) diets containing 1% squid liver oil (S7), 7% squid liver oil (S14), and a mixture of 2% soy lecithin and 5% squid liver oil (SL14) were formulated to obtain 7% and 14% of crude lipid. Triplicate groups of fish (6.3 ± 0.2 g) were fed to apparent satiation twice a day for 60 days. Weight gain, daily feed intake, feed efficiency and protein efficiency ratio were significantly higher for fish reared at 17 °C than at 12 °C. Daily feed intake was significantly decreased with the increase of dietary lipid level at the same water temperature, but weight gain was not affected by dietary lipid composition. At 12 °C, feed efficiency and protein efficiency ratio were significantly higher for fish fed the S14 and SL14 diets than those of fish fed the S7 diet, while at 17 °C feed efficiency and protein efficiency ratio of fish fed the S14 diet, which were not significantly different from those of fish fed the SL14 diet, were significantly higher than those of fish fed the S7 diet. There were no significant effects of dietary lipid composition or temperature range on the whole body contents of moisture, crude protein, lipid or ash. Dietary lipid composition and temperature affected the fatty acid content of the polar lipid from the liver; and the n-3HUFA contents such as 20:5n-3 and 20:6n-3 were higher at 12 °C than at 17 °C. The results of this study indicate that an increase of dietary lipid level from 7% to 14% has beneficial effects on feed utilization of flounder when reared in suboptimal water temperatures. The increase of water temperature from 12 to 17 °C improved growth and feed utilization, but 2% soy lecithin had no substantial effect on growth and feed efficiency of juvenile flounder.     

Effect of dietary supplementation of calcium chloride on growth,survival, moulting frequency and body composition of narrow‐clawed crayfish,Astacus leptodactylus (Eschscholtz, 1823)

The effects of dietary calcium chloride (CaCl₂) concentration on the growth, survival, moulting and body composition of Astacus leptodactylus were studied. Diets were prepared using supplementation of 0 (control), 30, 60 and 120 g kg^?1 calcium chloride commercial trout larvae diet containing 50% protein and 12% lipid. Astacus leptodactylus larvae with an average total length of 22.0 ± 0.05 mm (TL) and weight of 0.53 ± 0.01 g obtained from eighteen ovigerous females collected from Seydisehir Sugla Dam lake in Konya, Turkey, were stocked in 0.2‐m² aquariums at a rate of 50 crayfish m^?2 and reared for 90 days. The experiments included four treatments (diets) with three replicates each. Calcium chloride exerted positive effects on growth, moulting frequency, feed efficiency and survival of narrow‐clawed crayfish. Crayfish fed with 60 g calcium kg^?1 calcium chloride‐supplemented diet exhibited the highest weight gain and specific growth rate (SGR) but the lowest survival rate (63.3%) (P < 0.05). There were no significant differences (P > 0.05) in mean moisture (803.5 g kg^?1) and protein content (177.0 g kg^?1) in crayfish tail meat. However, lipid values were between 3.8 and 11.6 g kg^?1 and significantly different among the diets (P < 0.05). Diet with 60 g kg^?1 calcium chloride is recommended for the best growth of freshwater crayfish.     

The effect of different rotifer feeding regimes on the growth and survival of yellowtail kingfish Seriola lalandi (Valenciennes, 1833) larvae

First feeding success is critical to larval marine finfish and optimization of live feed densities is important for larval performance and the economics of commercial hatchery production. This study investigated various rotifer feeding regimes on the prey consumption, growth and survival of yellowtail kingfish Seriola lalandi larvae over the first 12 days post hatch (dph). The common practice of maintaining high densities of rotifers (10–30 ind. mL^?1) in the rearing tank was compared to a low density feeding technique, where 5–8 ind. mL^?1 of rotifers were offered. A ‘hybrid’ feeding regime offered rotifers at the high density treatment until 5 dph and the lower feeding densities thereafter. There was no significant difference in larval survival (hybrid: 28.9 ± 7%, low density: 17.3 ± 5% and high density: 17.2 ± 9%) or growth (hybrid: 6.12 ± 0.18 mm, low density: 6.03 ± 0.10 mm and high density: 6.11 ± 0.23 mm) between treatments. Rotifer ingestion was independent of rotifer density throughout the trial and increased with larval age, with larvae at 4 dph ingesting 22 ± 1.5 rotifers larvae^?1 h^?1 and by 11 dph ingesting 59 ± 1.6 rotifers larvae^?1 h^?1. These data demonstrate that from first feeding, yellowtail kingfish larvae are efficient at capturing prey at the densities presented here and consequently significant savings in rotifer production costs as well as other potential benefits such as facilitation of early weaning and improved rotifer nutritional value may be obtained by utilizing lower density rotifer feeding regimes.     

容器颜色对漠斑牙鲆白化率和成活率的影响

本文就培养容器的颜色对漠斑牙鲆稚鱼的白化率和生长率的影响进行初步研究。结果表明:用深蓝色和黑色等深色容器培养的稚鱼白化率显著低于白色和黄色等浅色容器(p<0.05),黑色、深蓝色、黄色和白色4个组别(N=100)的白化率分别为20.8%、14.4%、57.6%和86.6%;白色最高为86.6%,深蓝色最低为14.4%;而用不同颜色的容器培养漠斑牙鲆的稚幼鱼,对其成活率影响不大(p>0.05),黑色、深蓝色、黄色和白色4个组别的成活率分别为96.0%、90.0%、82.5%、93.0%;白化稚幼鱼的生长发育并无异常。     

Effects of different dietary lipid levels and fatty acids profile in the culture of white shrimp Litopenaeus vannamei (Boone) in biofloc technology: water quality,biofloc composition,growth and health

The objective of this study was to evaluate the influence of different dietary lipid and fatty acids on the nutritional value of bioflocs used as a feed, as well as shrimp performance and health. A total of 1800 Litopenaeus vannamei juveniles (2.87 ± 0.01 g) were cultured in biofloc technology, with a density of 200 shrimp m^?2, and fed with three isoproteic experimental diets at different lipid levels (85 g kg^?1, 95 g kg^?1 and 105 g kg^?1); each treatment was performed in triplicate. After 61 days, no significant difference was observed (P > 0.05) among the water quality parameters. For the shrimp performance, significant difference was observed (P = 0.011) among the values of survival, where treatments with lower lipid levels had higher survival (92.5 ± 3.5% and 91.0 ± 2.5%). Although there are significant differences in survival, no significant differences in the total haemocytes count (THC) were observed. For other growth performance, no differences were observed (P > 0.05). A positive correlation (r = 0.75) has been observed between the dietary oleic acid and bioflocs. The bioflocs showed ‘long‐chain’ polyunsaturated fat acids (lcPUFA), especially arachidonic acid. The shrimp showed similar growth and stayed healthy at the end of the experimental period.     

Pilot Production of Hatchery-Reared Summer Flounder Paralichthys dentatus in a Marine Recirculating Aquaculture System: The Effects of Ration Level on Growth, Feed Conversion, and Survival

Pilot‐scale trials were conducted to evaluate growout performance of hatchery‐reared summer flounder fingerlings in a state‐of‐the‐art recirculating aquaculture system (RAS). The outdoor RAS consisted of four 4.57‐m dia × 0.69‐m deep (vol. =11.3 m³) covered, insulated tanks and associated water treatment components. Fingerlings (85.1 g mean initial weight) supplied by a commercial hatchery were stocked into two tanks at a density of 1,014 fish/tank (7.63 kg/m³). Fish were fed an extruded dry floating diet consisting of 50% protein and 12% lipid. The temperature was maintained between 20 C and 23 C and the salinity was 34 ppt. Under these conditions, growth, growth variation (CV_wt), feed utilization, and survival of fish fed to 100% and 82% of a satiation rate were compared. Due to clear changes in growth patterns during the study, data was analyzed in three phases. During phase 1 (d 1–d 196), fish showed rapid growth, reaching a mean weight of 288 g ± 105 and 316 g ± 102, with a CV_wt of 0.36 and 0.32 and FCR's of 1.38 and 1.36 in the subsatiation and satiation groups, respectively. During phase 2 (d 196–d 454), fish displayed slower growth reaching mean weights of 392 g ± 144 and 436 g ± 121, with a CV_wt of 0.37 and 0.28, and increasing FCR's of 3.45 and 3.12 in the subsatiation and satiation groups, respectively. During phase 3 (d 454–d 614), fish showed little growth reaching mean weights of 399 g ± 153 and 440 g ± 129, with a CV_wt of 0.38 and 0.29 in the subsatiation and satiation groups, respectively. Over the entire growout period (d 1–d 614), feed conversion ratios were 2.39 and 2.37 and survival was 75% and 81 % in the subsatiation and satiation treatments, respectively. The maximum biomass density reached during the study was 32.3 kg/m³. The satiation feed rate was superior to the 82% satiation rate, since it maximized growth rates, with no effect on FCR. The higher CV_wt in the subsatiation group suggests increased competition for a restricted ration led to a slower growth with more growth variation. The decrease in growth in phases 2 and 3 was probably related to a high percentage of slower growing male fish in the population and the onset of sexual maturity. This study demonstrated that under commercial scale conditions, summer flounder can be successfully grown to a marketable size in a recirculating aquaculture system. Based on these results, it is recommended that a farmer feed at a satiation rate to minimize growout time. More research is needed to maintain high growth rates through marketable sizes through all‐female production and/or inhibition of sexual maturity.