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1.
Abstract.— Two 10-d hatchery growth trials were conducted to determine if differences in growth, body composition, and survival existed among catfish fry Ictalurus punctatus fed a diet of 100% catfish-starter (CS) or CS in combination with decapsulated Artemia cysts (DAC) at 25%, 50 % , or 75% of diet weight. A 120–d production trial was undertaken immediately following the first hatchery trial to evaluate the effects of diet on production characteristics (survival, length, weight, feed conversion ratio, and total yield) of fingerling catfish produced from hatchery-raised fry. Fry fed diets containing DAC weighed 61–98% more ( P < 0.05) than fry fed only CS. The size differential of DAC-fed fry was maintained through 120 d of growth in simulated nursery ponds (0.001-ha earthen-bottom pools). The increased growth of fry fed DAC might have been related to differences in dietary lipid content, amino acid composition, or digestibility of CS and DAC. Body weights of fingerlings produced under simulated production conditions from fry fed hatchery diets containing 50% and 75% DAC were 17% and 25% higher, respectively, 130 d post-hatch, than fingerlings produced from fry fed only CS. In addition, the total yield of fingerlings produced from fry fed 75% DAC was 17% greater that that of fingerlings produced from fry fed only CS. The increased performance of fingerlings produced from DAC-fed fry could have resulted from their larger size at stocking, since larger fry might be capable of capturing natural food organisms and ingesting prepared diets more effectively than smaller fish. CS-DAC diet combinations could be used to increase weight gain of hatchery-raised fry if the cost-benefit ratio of adding DAC to the standard hatchery diet warrants its use.  相似文献   

2.
Paddlefish are gaining increasing acceptance as an aquaculture species worldwide. Commercial trout feeds, containing high protein and lipid levels, are currently used in intensive culture; however, nutritional requirements of paddlefish are not currently known. A study was conducted examining the effects on growth, survival and fillet composition of juvenile paddlefish when fed commercial feeds differing in protein and lipid levels. Paddlefish larvae were first stocked in 14.0 m3 round tanks and fed trout starter feeds for 43 days until trained to accept a 1.6 mm pellet. Paddlefish juveniles of mean weight (±SE) 20±0.27 g were randomly stocked into six0.02 ha ponds at 12 500 ha?1 and fed floating commercial trout or catfish (lower protein and lipid) feeds, twice daily (08:00 and 15:30 hours) for 92–97 days. At harvest, there were no significant differences in final weight, percent survival, specific growth rate , relative growth and feed conversion ratio between treatments, which averaged 223.6 g, 96.2%, 2.5% day?1, 10.2 and 1.98 respectively. Surface feeding activity index was significantly higher in ponds supplied with catfish feed than in ponds supplied with trout feeds. Relative pellet buoyancy was not a factor in feeding activity. Fulton's condition factor averaged0.238, was not significantly different, and was similar to a reported value for extensively cultured paddlefish (zooplanktivore). There was no significant difference in liver somatic index between treatments, which averaged 1.91%. Percent protein and moisture of fillets averaged 14.9% and 80.9%, respectively, and were not significantly different between treatments. However, lipid content of fillets was significantly higher in paddlefish fed the trout feed (4.45%), compared with paddlefish fed the catfish feed (2.42%). Fillet lipid content for both treatments was higher than reported values for extensively cultured paddlefish. Percent abdominal fat was significantly higher (0.82%) in paddlefish fed the trout feed compared with paddlefish fed the catfish feed (0.52%). Results from this study indicate that paddlefish can be fed a commercial catfish feed labeled to contain 32% protein and 4.5% lipid without adverse effects on growth, survival and fillet composition, lowering production costs.  相似文献   

3.
Abstract– Experimental comparisons were made between release as unfed fry and release as six weeks fed parr, upon the growth and final population density of young salmon and trout over a ten week period. Salmon and trout released into experimental channels as unfed fry at densities of about 19 fish. m-2 showed rapid reduction in numbers, chiefly by downstream dispersal, accompanied by negligible growth. After substantial reduction in numbers, there was a reduced rate of dispersal and rapid growth. Salmon and trout retained in a hatchery at high density (80 to 200 fish. m-2) and fed for six weeks on proprietary food showed slow, but measurable, growth. After release into the channels these fish adjusted their numbers, mainly by downstream dispersal, and showed an increased growth rate. At the end of a ten week period, salmon introduced as fed parr had approximately twice the population density of salmon introduced as unfed fry. No similar difference in population density could be shown for trout. For both species, the fish introduced as fed parr had a lower mean weight after ten weeks than had the fish introduced as unfed fry.  相似文献   

4.
Intensive tank rearing of channel catfish (Ictalurus punctatus Rafinesque) fry can be successfully accomplished with commonly available ‘salmonid’ starter diets. Ingredient substitution in starter diets is less important from the cost perspective but growth, survival and health of fish are major concerns. Several combinations of fish meals and animal protein substitutes were evaluated in diet formulations for hatchery rearing of catfish fry. Sub‐optimal thermal conditions were used which are characteristic for the north‐central USA where catfish culture is important for stocking purposes and live‐fish markets. A diet formulated on the basis of menhaden fish meal (29.1%), herring fish meal (25.1%) and animal by‐product mixture (16.38%) gave numerically the highest growth rate after 13 weeks of feeding, although growth reductions in fish fed diets exclusively with mehaden meal (77.6%) as protein or substituted with 50% animal by‐product protein were not significant. Instantaneous mortality rates were the highest between weeks 2 and 4 of rearing and increased almost proportionally with the increased fish meal protein substitution. A diet based on menhaden fish meal had the highest concentration of phosphorus and several other essential minerals, but these were not reflected in the mineral composition of the fish body at the termination of feeding. Among activities of digestive enzymes, trypsin was depressed in fish offered diets with 75–100% fish meal protein replacement. A diet superior in terms of fish performance was defined in the present study and it was concluded that the initial feeding can greatly affect physiological status of juvenile channel catfish.  相似文献   

5.
Plant protein sources were evaluated in 32% protein grow-out feeds for channel catfish (initial weight: 180 g/fish) stocked at high densities (24,700 fish/ha) in 0.04 ha earthen ponds. Each of the eight practical-type feeds was assigned for five replicate ponds. The fish were fed to satiation once daily for 170 d. Specifically, cottonseed meal and cottonseed meal plus supplemental lysine were evaluated as replacements for soybean meal. Soybean meal, a combination of soybean meal and cottonseed meal, or a combination of soybean meal and cottonseed meal plus supplemental lysine were evaluated as a substitute for animal protein sources. Based on weight pin, feed conversion ratio, body composition, percentage visceral fat, and dressed yield, the data indicated that cottonseed meal plus lysine can be used as a total substitute for soybean meal in catfish feeds. However, it is not recommended that more than 30% cottonseed meal be used in catfish feeds until additional data are available on the effects of gossypol on reproduction in catfish. Also, data indicated that plant proteins can be used as a total replacement for animal protein without detrimental effects. Reduced weight gain was observed in fish fed a feed that contained 68% of the established available lysine requirement. However, fish fed feeds estimated to contain only 76 or 82% of the available lysine requirement did not show reduced weight gain. This suggests that lysine may be more highly available from cottonseed meal than previously estimated, or that natural food organisms in the pond contributed nutrients including lysine, or that fish were able to consume enough of the marginally deficient feeds to meet their requirement for lysine. This study was conducted with large catfish fed a 32% protein feed to satiation once daily. If smaller fish, a lower protein fed, or a restricted feeding regimen had been used, the results may have been different.  相似文献   

6.
Growth of larval sharptooth catfish Clarias gariepinus fed live Artemia nauplii , a specially prepared dry feed (MN-3), a commercial dry salmon starter feed (Silver Cup 3600), or a combination of 50% live Artemia and 50% MN-3, under conditions of either light or dark for 21 days was studied. For all diets, fish reared in darkened tanks were significantly larger than those in illuminated tanks from day 8 onwards. Fish fed a combination of live Artemia plus MN-3 grew significantly more quickly than those fed either live Artemia or MN-3 only. On day 21 of the experiment, average weight of fish fed the combined diet was 649 ± 30 mg (mean ± SEM ) in darkened tanks and 445 ± 16 mg in illuminated tanks, while those fed Artemia alone were 242 ± 9 and 198 ± 13 mg (dark and light, respectively) and fish fed MN-3 only were intermediate at 377 ± 20 and 267 ± 16 mg (dark and light, respectively). Catfish fed the salmon starter initially grew slowly, but after day 11 grew more quickly than the other groups. Mortalities were highest for fish fed salmon feed.
Permanent darkness enhances the growth of C. gariepinus larvae during and after metamorphosis. While dry diets promoted higher growth rate than live Artemia nauplii alone, a combination of the two resulted in the fastest growth.  相似文献   

7.
The suitability of some common, natural and artificial feedstuffs for the rearing of fry of Clarias lazera (C. & V.) was investigated in 2 experiments.It was found that a dry trout starter, an experimental dry feed and dried inactive yeast were not suitable feeds for rearing C. lazera fry. Neither could ground Clarias fingerlings or frozen zooplankton be used. By contrast, frozen Artemia and especially live Artemia and live zooplankton gave good results. After 4 weeks the fish thus fed had attained an average weight of 0.3 to 1 g and survival ranged from 50 to 96%.Feeding in excess of satiation and feeding 24 h/day gave the fastest growth, although the differences in comparison with feeding Artemia or live zooplankton to satiation 4 times per day were not significant. The specific growth rate (% body weight) of these fish decreased from 68% at the start of the experiment to 9% after 28 days.  相似文献   

8.
The suitability of meals derived from fish processing wastes as the protein fraction in practical diets for hatchery-reared coho salmon was investigated. The study compared the performance of coho salmon fed diets containing three products: a skin-and-bone meal (SB), a deboned meal (DM), and a whole-fish meal (WM) made directly from the fish wastes. A commercial trout diet (CO) was fed to a fourth treatment group. Diets were fed at 3% of body weight per day to juvenile coho salmon for 12 wk. Survival (> 94%) was not significantly different among treatment groups. Average fish weight, feed conversion ratio, whole body proximate and mineral composition, and protein and phosphorus retention were compared. There were no significant differences after 12 wk of feeding in fish weight between WM, DM, and CO, but SB had significantly lower weight and whole body lipid, and significantly higher ash. Compared to WM, DM had a significantly lower feed conversion ratio and higher retention of protein and phosphorus, but these indices were not significantly different from CO. It is concluded that DM is a potentially superior protein ingredient compared to WM, while specific characteristics of SB will limit its use as a protein source in feeds for salmonids. However, SB may prove to be a suitable mineral supplement when added at a low level. Utilization of fish processing wastes in salmonid diets could be a commercially viable alternative to direct disposal of processing wastes.  相似文献   

9.
Largemouth bass (LMB) Micropterus salmoides fry do not accept prepared diets at first feeding. Fry are initially reared in fertilized ponds on natural live foods until large enough to be feed trained. Unpredictable weather patterns and depletion of natural forages can affect nursery pond survival. A series of experiments was conducted to investigate the use of Artemia nauplii prepared diets and optimal feeding schedules to raise LMB fry from first feeding through habituation to a commercial dry diet. In Studies 1, 2, and 3, swim-up fry were transferred to a recirculating system and stocked into either 3-L (Studies 1 and 2) or 10-L (Study 3) acrylic aquaria. Study 1 screened candidate diets to evaluate whether LMB fry could be transitioned directly to prepared diets or if they required live foods. In Study 2 the optimum duration for feeding live Artemia (1, 2, or 3 weeks) and the appropriate size of commercial diets (<200 or 200–360 μm) were evaluated. Study 3 was designed to identify the best transitional feed. Results from Study 1 indicate that fry fed Otohime-A (<200 μm) and decapsulated Artemia cysts performed better than those fed other diets tested. However, survivals were low (6%–8%) indicating a need for live feed initially. In Trial 2, fry fed live Artemia nauplii for two weeks and then transitioned to a 200–360 μm diet (Otohime-B) performed better than other diet combinations tested. In Study 3, survival was significantly higher in treatments using decapsulated Artemia cysts or Otohime-B as transitional diets between initial live Artemia feeding and trout starter. These data indicate that LMB fry can be successfully raised from first feeding to fully habituated to a commercial trout starter by feeding live Artemia nauplii for two weeks, followed by a gradual transition to either decapsulated Artemia cysts or Otohime-B for one week, then gradually transitioning to trout starter. Surviving fish were easily transitioned to commercial floating feed (Study 4). This protocol yielded survival rates of approximately 70% and may improve the reliability of LMB fingerling production by eliminating the outdoor nursery pond phase.  相似文献   

10.
Abstract – The possibility to increase the proportion of migrating hatchery‐reared smolts by reducing their food ration was studied. Lake‐migrating, hatchery‐reared salmon (Salmo salar) and trout (Salmo trutta) smolts were either fed normal rations, based on recommendations from the fish‐farming industry, or reduced (15–20%) rations. They were released into the River Klarälven, western Sweden, and followed as they swam downstream to Lake Vänern, a distance of around 25 km. For both Atlantic salmon and brown trout, smolts fed a reduced ration migrated faster than fish fed a normal ration. Furthermore, a higher proportion of salmon smolts fed reduced rations migrated to the lake than fish fed normal rations in 2007 but not in 2006. This difference between years corresponded to greater treatment differences in size and smolt status in 2007 than in 2006. For trout, the proportion of migrating individuals and smolt development did not differ with ration size. Trout migrants fed a normal ration had a higher standard metabolic rate (SMR) than nonmigrants, whereas there was no difference in SMR between migrating and nonmigrating salmon. These results show that it is possible to use a reduced food ration to increase the migration speed of both Atlantic salmon and brown trout and to increase the proportion of migrating Atlantic salmon.  相似文献   

11.
本试验评估了(Ictalurus punctatus)主产区4种商品颗粒饲料(分别记为S1、S2、S3和S4,其中S4为膨化饲料,其他均为颗粒饲料)和自行设计的颗粒饲料(记为S5)对试验阶段生长性能、体色变异、肝胰脏组织结构及形态指标的影响。7周的饲喂试验结果显示:饲料蛋白含量为38%的S4膨化饲料可明显的提高养殖鱼的体重,平均增重率为262.6%,但存活率较低,仅为72.3%;而喂养S5饲料组的增重率为168.89%,且存活率为92.4%,高于其他饲料组。养殖结束后,不同试验组的肥满度、脏体比有所差异,但均未达到显著性水平(P>0.05)。投喂S2饲料组养殖鱼体体色发白比较明显,体色异常比例高达91%;S4饲料组养殖后体色发白也比较明显,体色异常比例为72.3%;对背部黑色素扫描研究进一步证实饲喂S2饲料和S4饲料的黑色素细胞发生了变化,黑色素细胞边缘变得模糊,而自配S5饲料的黑色素细胞树突状分支较多;饲喂S4饲料组的背部斑点比例为12.15%,而S2饲料组的背部斑点比例为26.38%,自配S5饲料组的背部斑点比例为35.69%,S4饲料组的斑点比例明显较低。  相似文献   

12.
Cottonseed meals were evaluted as partial and complete replacements for soybean meal in pond feeds for channel catfish grown at densities of 5,300/ha. The following dietary treatments were used: 1) glanded cottonseed meal (GC) in which ½ of the soybean meal was replaced; 2) glandless cottonseed meal (GLC) in which all of the soybean was replaced, 3) a control feed (C) typical of commercial catfish feeds. The feeding trial was conducted in 0.04 ha earthen ponds for a period of 176 days. Natural prey species were present in all ponds. Final weights and condition factors of fish fed the GC feed were reduced compared to those fed the GLC or C feeds. This response did not appear to be related to dietary gossypol levels. Even though the GLC feed appeared to be deficient in available lysine, final weight and feed conversion of fish fed the GLC feed were equal to those fed the C feed. Possible nutrient contributions of natural food available in the ponds could not be determined. There were no significant differences in feed conversions or dressout percentages of fish regardless of dietary treatment. Fish fed the GLC feed exhibited a higher percentage of fat and lower percentages of moisture, protein and ash (dry weight basis) in edible tissue than fish fed the other feeds. Free gossypol levels in edible fish tissue were below 100 ppm.  相似文献   

13.
The ability of poultry products to replace fish meal in diets for rainbow trout, Oncorhynchus mykiss, depends on their nutrient composition, cost, and consistency. The aim of this study was to assess the ability of three commercially available poultry products (chicken concentrate, CC, poultry by‐product blend, PBB; or chicken and egg concentrate, CE) to maintain growth and disease resistance when substituted for fish meal in a rainbow trout starter diet. A control diet was formulated to contain 48% crude protein and 18% crude lipid; 100% of the fish meal in test diets was replaced with CC, PBB, or CE. At stocking, fry were counted into groups (50 fish/tank) with six replicate tanks for each diet and fed their respective diets four times daily for 8 wk. All the poultry‐based diets supported growth (over 1600% increase over initial weight), nutrient retention, and feed conversion ratios of rainbow trout fry equal to or greater than those observed for fry fed with the fish meal‐based diet. No effect of diet on survival was observed following subcutaneous injection challenge with Flavobacterium psychrophilum. These data suggest that the examined products can be used in place of fish meal for rainbow trout fry without lowering growth and disease resistance.  相似文献   

14.
A 10-wk feeding trial was conducted in the laboratory during which channel catfish Ictalurus punctatus (average initial weight: 6.5 g/fish) were fed five practical diets containing either 0, 500, 1,000, 2,000, or 4,000 units of microbial phytase/kg diet. Fish fed diets containing 500 or more units of microbial phytase/kg consumed more feed and gained more weight than fish fed the basal diet without supplemental phytase. Feed conversion ratios (FCR) did not differ among treatments except the FCR for fish fed 1,000 units of microbial phytase/kg diet was lower than that of fish fed no supplemental phytase. Fish survival was not different among treatments. Contrast analysis showed that weight gain, feed consumption, bone ash, and bone phosphorus were higher and feed conversion ratio was lower for fish fed diets supplemented with phytase as compared to fish fed no supplemental phytase. The concentration of fecal phosphorus decreased linearly as phytase supplementation increased. Results from this study demonstrate that microbial phytase is effective in improving bioavailability of phytate phosphorus to channel catfish, which may eventually lead to a reduction in the amount of supplemental phosphorus added to commercial channel catfish feeds.  相似文献   

15.
Two marine algal products MAP3 and MAP8 were examined for their suitability as fishmeal protein substitutes in feeds of three prominent farmed species, through short‐term feeding studies. Algal meals were tested at 5 and 10% protein replacement levels for Atlantic salmon and at 25 and 40% for common carp and whiteleg shrimp. At the end of the 12‐week period, the growth and feed performance of the two fish species did not reveal any significant difference between those fish offered the algae‐based feed and those offered the control feed. The whole body proximate compositions of Atlantic salmon fed the control and algae‐based feeds were not significantly different. In common carp, the lipid content in the fish fed higher level of MAP3 was significantly lower than that of the fish fed the control feed. In whiteleg shrimp, at the end of the 9‐week feeding period, growth performance and feed utilization did not differ between the treatment groups. Protein content in the shrimp fed the higher level of MAP8 was significantly lower than that of shrimp on the control feed. The three species could accept the algal meals in their feeds at the tested levels, though there were some noticeable effects on body composition at higher inclusion levels.  相似文献   

16.
Rainbow trout, average weight 185–187 g, were fed feeds containing menhaden oil, canola oil or fish oils (pollock, pink salmon or rockfish) produced from Alaskan seafood processing waste as the added oil for 8 weeks, at which time the fish weighed 391–411 g (average 404 g, pooled SE = 5.7). The fish were previously fed from 75 g average weight fed commercial feed containing poultry oil as the added oil. No significant differences were measured in final weight or feed conversion ratio among dietary treatment groups. Significant differences were found in fillet ω‐3 fatty acid (FA) levels from fish receiving fish oil‐supplemented feeds compared to those from fish receiving feeds containing canola oil. Fillet contents of eicosapentaenoic acid (EPA; 20:5ω3) and decosahexaenoic acid (DHA; 22:6ω3) were highest in the pollock oil treatment group, although all fish oils increased highly unsaturated ω‐3 FA contents (mg 100 g?1) of fillets. Fish oil used through the production cycle was reduced by 25% by supplementing feeds with poultry oil during the middle phase of production (75–175 g) compared to using feeds containing fish oil throughout the production cycle. Fish oils recovered from Alaskan seafood processing waste were suitable alternatives to conventional fish oil as ingredients in rainbow trout production feeds.  相似文献   

17.
Use of Cottonseed Meal in Channel Catfish Feeds   总被引：3，自引：0，他引：3  
Solvent extracted cottonseed meal was substituted for soybean meal in catfish feeds on a nitrogen basis. The feeds, which contained either 0, 10, or 20% cottonseed meal, were formulated to contain about 32% protein and 2.9 kcal digestible energy/g. The fish were reared in 6 m3 net pens suspended in a 1.6 ha earthen pond. Twelve pens (four per treatment) were stocked with 400 fish with an initial average weight of 95 g/fish. All fish were fed to satiation once daily. A sample of 60 fish from each pen was weighed at 76 days to evaluate feed consumption, feed conversion, and weight gain. At the end of the experiment (132 days), fish from each net pen were weighed collectively and samples were taken to determine tissue free gossypol concentrations, proximate composition of fillets, and dressout percentages. There were no significant differences in weight gain, feed conversion, or survival of fish sampled at 76 days or of fish at the end of the experiment regardless of dietary treatment. At 76 days, feed consumption of fish fed the 20% cottonseed meal feed was significantly higher than that of other fish, but there were no significant differences in feed consumption at the end of the experiment. Free gossypol levels were below detectable limits in fish tissue. There were no significant differences in percentage dressout or in body composition, except for a slightly higher ash content in fish fed the feed containing 10% cottonseed meal. It appears that cottonseed meal can be used to partially substitute for soybean meal in catfish feeds. At the present, it is recommended that cottonseed meal be limited to 15% of the catfish diet.  相似文献   

18.
Fishery processing by‐products are a large resource from which to produce fishmeal and other products for a variety of uses. In this study, testes meal (TM) produced from pink salmon processing by‐product was evaluated as a functional ingredient in aquafeeds. Nile tilapia and rainbow trout fry were fed five isonitrogenous and isoenergetic experimental diets for 4 and 9 weeks respectively. Two diets were fishmeal‐based (FM) and three were plant protein‐based (PP). Salmon TM was added to the FM and PP diets at 7% to replace 20% of fishmeal protein (FMTM and PPTM respectively). An additional control diet was prepared in which fishmeal was added to the PP diet to supply an equivalent amount of protein as supplied by TM (PPFM). Inclusion of TM in both the FM‐ and PP‐based diets resulted in higher final body weights, although differences were only significant between rainbow trout fed FM or FMTM diets. Similar differences were calculated for other indices of fish performance, e.g. specific growth rate, feed conversion ratio, protein efficiency ratio and protein retention efficiency. Feed intake was significantly higher for fish fed FMTM compared with FM in rainbow trout. For tilapia, final weights were numerically higher, but not significantly different for fish fed diets containing TM compared with non‐TM diets (FM vs. FMTM; PP vs. PPTM). Performance of trout or tilapia fed the PPFM diet did not increase compared with the PP diet. The results indicate that TM addition to both FM and PP diets increased feed intake and also increased metabolic efficiency, demonstrating that TM can be a functional ingredient in aquafeeds.  相似文献   

19.
Two experiments were conducted to identify appropriate experimental and practical diets for bluegill Lepomis macrochirus and hybrid bluegill L. cyanellus × L. macrochirus reared in aquaria. In the first study, four experimental diets and five commercial diets were evaluated in juvenile hybrid bluegill initially weighing 4.8 g/fish. The experimental diets contained casein (CAS), casein + gelatin (CAWGEL), casein + L‐arginine‐HCI (CAS/ARG), or casein + gelatin + crystalline amino acids (CAS/AA) as sources of crude protein. The commercial diets included three diets formulated to meet the nutritional requirements of rainbow trout Oncorhynchus mykiss and two diets formulated to meet the nutritional requirements of channel catfish Ictalurus punctatus. Each diet was fed twice daily at a rate of 4% of body weigh/d to triplicate groups of fish. At the end of the 8‐wk feeding trial, weight gain was significantly higher in fish fed the best commercial rainbow trout diets (205–217%) compared to fish fed diets formulated for channel catfish (87–104%). Weight gain and feed efficiency (FE) of fish fed the experimental diets (5346% and 0.19–0.32, respectively) were significantly lower than those of fish fed the commercial rainbow trout diets (143–217% and 0.49–0.64, respectively). In the second experiment, the same dietary treatments were fed for 8 wk to juvenile bluegill initially weighing 3.7 g/fish. Each diet was fed twice daily at a rate of 4% of body weight/d to triplicate groups of fish. Weight gain was significantly higher in fish fed commercial trout diets (291–402%) compared to fish fed diets formulated for channel catfish (164–191%). Weight gain and FE of fish fed CAS/ARG were significantly higher than those of fish fed the commercial catfish diets, but significantly lower than those of fish fed the best commercial trout diets. Results of this study indicate that commercial rainbow trout diets are preferable to commercial channel catfish diets for culture of bluegill and hybrid bluegill. More research is needed to identify appropriate experimental diets for this group of fishes.  相似文献   

20.
Non‐native predators may interfere with conservation efforts for native species. For example, fisheries managers have recently become concerned that non‐native brown trout may impede efforts to restore native salmon and trout in California's Trinity River. However, the extent of brown trout predation on these species is unknown. We quantified brown trout predation on wild and hatchery‐produced salmon and trout in the Trinity River in 2015. We first estimated the total biomass of prey consumed annually by brown trout using a bioenergetics model and measurements of brown trout growth and abundance over a 64‐km study reach. Then, we used stable isotope analysis and gastric lavage to allocate total consumption to specific prey taxa. Although hatchery‐produced fish are primarily released in the spring, hatchery fish accounted for most of the annual consumption by large, piscivorous brown trout (>40 cm long). In all, the 1579 (95% CI 1,279–1,878) brown trout >20 cm long in the study reach ate 5,930 kg (95% CI 3,800–8,805 kg) of hatchery fish in 2015. Brown trout predation on hatchery fish was ca. 7% of the total biomass released from the hatchery. Brown trout only ate 924 kg (95% CI 60–3,526 kg) of wild fish in 2015, but this was potentially a large proportion of wild salmon production because wild fish were relatively small. As large brown trout rely heavily on hatchery‐produced fish, modifying hatchery practices to minimise predation may enhance survival of hatchery fish and potentially reduce the abundance of predatory brown trout.  相似文献   

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