摘要:

AbstractThe effects of temperature, salinity, irradiance and pH on the growth ofFibrocapsa japonica(Raphidophyceae) were examined to determine how environmental factors affect the distribution of this species. Optimal growth was observed at temperatures of 15–25 C, salinities of 25–35 parts per thousand (ppt), irradiances of 60–140 μmol quanta/m2per s and pH between 7.5–8.5. Growth did not occur at temperatures below 10 C or above 30 C nor at salinities below 15 ppt.Fibrocapsa japonicagrew when subjected to irradiances of 20–180 μmol quanta/m2per s, and could tolerate a pH range

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00606.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe ichthyotoxicity and toxin composition of a red‐tide producing chloromonadFibrocapsa japonica(Toriumi and Takano) were examined. The flagellate showed the highest toxicity in mid‐logarithmic phase and the lowest in the stationary phase with increased number of spherical‐shaped cells. Five neurotoxic components, FjTx‐I, FjTx‐II, FjTx‐IIIa, FjTx‐IIIb and FjTx‐IV, which corresponded to brevetoxin components, PbTx‐1, PbTx‐2, PbTx‐9, PbTx‐3 and oxidized PbTx‐2 were tentatively identified from analysis ofF. japonicatoxins on TLC and HPLC. The quantity of each component fluctuated with the age and growth stage of the culture. Among the five toxic components the yield of FjTx‐II per cell was highest in both logari

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00607.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractRainbow troutOncorhynchus mykissfry were reared at four densities ranging from 10,800 to 43,926 fish/m3(9.91 to 37.60 kg/m3) during an initial feeding period of 35 d. Each of the four initial density treatments were then split into high (3,780 fish/m3) and low (1,890 fish/m3) density groups and reared in outdoor raceways for an additional 74 d. A necropsy‐based general health and condition assessment indicated that hematocrit, plasma protein, and the thymus index were significantly elevated in the outdoor high density group. Changes in these variables were unrelated to the initial rearing density, except for plasma protein which decreased as the initial density increased at low densities. Other necropsy variables indicated normal, healthy fish. Agonistic behavior was assessed at 4, 9 and 13 wk of age by observing the number of aggressive chases in paired and group (five fish) trials. The number of chases generally increased with age, although the difference between 9 and 13 wk was variable. Feeding did not elicit more chases in this study except for 9‐wk‐old fry. Initial rearing density did not have any impact on the number of chases at 4 or 13 wk, but at 9 wk the number of chases increased with initial density for the group tests. Relative fin length measurements of all fins except the adipose indicated no combination of initial density and outdoor density was superior to another for reducing fin erosion. This study indicated that rainbow trout fry may be reared at initial densities approaching 44,000 fish/m3(Piper density index of 1.1) without negatively affecting growth and fin condition or inducing higher levels of agonistic behavior lat

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00608.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractAn economic analysis was performed of a proposed commercial‐scale 20‐ha saltwater pond culture operation for Florida red tilapia in Dorado, northern Puerto Rico. The analysis was based on actual cost and production data from a commercial‐scale hatchery, pilot‐scale grow‐out trials conducted in six 0.2‐ha saltwater (avg. = 22.7 ppt) ponds at the Dorado facility and on wholesale market prices ($4.96–5.18/kg) fetched by dressed‐out (gilled, gutted and scaled) product. The proposed 20‐ha growout facility is comprised of 25 0.8‐ha earthen ponds, each supplied with sea water, brackish well water, drainage and aeration, which account for 60.8% of the capital costs. Ponds are stocked with fingerlings (0.85 g avg. wt.) at a density of 3.0 fish/m2(30,000/ha), and are harvested at 160 and 220 d, at an average weight of 545 g for a total yield of 11,445 kg/ha per crop. Imported feed ($0.55/kg), processing and distribution ($0.50/kg) and sex‐reversed fry ($0.11/fry) are the highest variable costs, accounting for 30.7%, 15.4% and 13.9%, respectively, of the total annual costs. Salaries and benefits, and depreciation represent the highest fixed costs, accounting for 8.4% and 5.5%, respectively, of the total annual costs. Under these conditions, a wholesale price of $4.55/kg results in a positive cash flow by year eight, and a breakeven price, internal rate of return (IRR), net present value (NPV) and discounted payback period (DPP) of $4.08/kg, 7.6%, ($235,717) and>10 yr, respectively, suggesting that the proposed 20‐ha operation is not economically feasible under these conditions. The proposed enterprise is marginally feasible if stocking density is increased to 3.5 fish/m2while at 4.0 fish/m2economic outlook is favorable. Costs can be lowered considerably by targeting production and market variables most sensitive to profitability indices, using locally‐prepared feeds, and vertically integrating hatche

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00609.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe dietary iron requirement for normal growth and optimum hematological values and bioavailability was determined for channel catfishIctalurus punctatusfingerlings using egg‐white based diets supplemented with 0,5,10,20,60, and 180‐mg iron/kg from iron methionine or 20, 60, and 180‐mg iron/kg from iron sulfate. The basal diet which contained 9.2‐mg iron/kg, 34% crude protein and 3.1 kcal of digestible energy/g was fed to channel catfish fingerlings (8.5 g) in triplicate flow‐through aquariums to satiation twice daily for 8 wk. Fish fed the basal diet without iron supplementation exhibited poor growth throughout the 8‐wk period. Fish fed iron‐supplemented diets did not differ with regard to final weight gain. Survival, feed conversion, total blood cell count, mean corpuscular hemoglobin concentration, serum iron, total iron binding capacity, and transferrin saturation were not significantly affected by dietary iron level. Hemoglobin, hematocrit, mean corpuscular hemoglobin, and mean corpuscular volume were significantly lower in fish fed the basal diet. These values were also consistently lower for fish fed diets with 5 and 10‐mg iron/kg from iron methionine. However, differences were not always significant. Results of this study indicate that supplementation of 5‐mg iron from iron methionine was sufficient for growth. However, a supplemental iron level of 20‐mg/kg diet or a total iron level of 30‐mg/kg of diet appeared to be needed for optimum hematological values. Iron methionine and iron sulfate were equally effective in preventing anem

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00610.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe efficacy of using weight gain and bone mineralization to estimate phosphorus availability from feed ingredients for channel catfish was investigated at the conclusion of a 12‐wk feeding trial. Juvenile channel catfish (initial weight = 7.8 g/fish) were fed one of seven test diets each containing phosphorus from a single source. All diets were isocaloric, isonitrogenous, and met all nutrient requirements of channel catfish except for phosphorus, which was assumed to be the factor limiting growth. Phosphorus was considered to be 90% available to fish fed the diet containing monosodium phosphate, but a relative value of 100 was assigned to this treatment for purposes of comparison. All other availability values were calculated relative to this value. Phosphorus availabilities (based on weight gain) for wheat middlings, cottonseed meal, and soybean meal were 38%, 43%, and 49%, respectively, which are in the range previously reported for channel catfish. Phosphorus availability values (based on weight gain) for dicalcium phosphate, menhaden fish meal, and meat and bone/blood meal were 82%, 75%, and 84%, respectively. These values were considerably higher (93–96%) than previously reported for catfish when based on bone ash or bone phosphorus. However, availability data based on weight gain for feedstuffs of animal origin generally agreed with phosphorus availability data reported for rainbow trout. Based on our data, mineral utilization by animals in general, and on known physiology of channel catfish, we suggest that weight gain may be a reliable indicator of phosphorus availability and that phosphorus availability values may be overestimated when base on bone mineralizat

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00611.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThree experiments were conducted to evaluate the need for supplemental phosphorus in the diet of channel catfishIctalurus punctatusas well as to compare dicalcium phosphate and defluorinated phosphate as sources of supplemental phosphorus. Fingerling channel catfish were stocked into 0.04‐ha earthen ponds at a rate of 1,000 fish/pond (24,700ha). The fish were fed a feed typical of commercial catfish feeds containing 28% protein and 2.8 kcal digestible energy/g once daily to satiation during the growing season (April to October). Fish in experiment 2 were overwintered and fed at a rate of 1% body weight twice weekly when the water temperature exceeded 13 C. The basal diet used in experiments 1 and 2, which contained no supplemental phosphorus, had estimated available phosphorus concentrations of 0.26 and 0.20%, respectively. Dicalcium phosphate was added to provide available phosphorus concentrations of 0.34 and 0.41% for experiment 1, and 0.27 and 0.35% for experiment 2. Diets used in experiment 3 to compare dicalcium and defluorinated phosphates contained 0.40% available phosphorus. Data from experiments 1 and 2 indicated that a concentration of dietary phosphorus of about 0.27% was adequate for maximum weight gain and efficient conversion of feed by channel catfish. However, a concentration of about 0.35% available phosphorus was required for maximum bone mineralization in experiment 2. There were no differences in growth or bone mineralization between fish fed dicalcium or defluorinated phosphate. We conclude that the small increase in bone phosphorus (about 4%) is biologically insignificant, and suggest that 0.3% available phosphorus be adequate for channel catfish raised in earthen ponds. Also, either dicalcium or defluorinated phosphate can be used as a source of supplemental phosphorus in channel catfish diets. However, defluorinated phosphate may be desirable because of its low solubility in wate

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00612.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractA 10‐wk feeding trial was conducted in the laboratory during which channel catfishIctalurus 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 feed

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00613.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractA docosahexaenoic acid (DHA), 22:6(n‐3), rich strain ofSchizochytriumsp. was used in a spray‐dried form to evaluate the enhancement of highly unsaturated fatty acids (HUFAs) inArtemia franciscananauplii (Utah biotype) and the rotiferBrachionus plicatilis. This heterotrophic microalga was selected because of its high concentration of the longest chain HUFAs in the n‐3 and n‐6 series, DHA and docosapentaenoic acid (DPA), 22:5(n‐6), respectively. When 24‐h‐oldArtemianauplii were fed 400 mg/L of the algae for 24 h, the DHA content of the nauplii went from undetectable levels to 0.8% of dry weight and the omega‐3 HUFA eicosapentaenoic acid (EPA), 20:5n‐3, content went from 0.1% to 0.5% of dry weight in the nauplii. Similarly, 22:5(n‐6) increased in the nauplii from undetectable levels to 0.4% of dry weight, with a concomitant increase in arachidonic acid, (20:4n‐6), from trace to 0.3% of dry weight even though there was no arachidonic acid in the algal biomass. Similar enrichment patterns were observed in rotifers. The results suggest that spray‐dried cells ofSchizochytriumsp. are effective in enrichingArtemianaupli and rotifers in both n‐3 and n‐6 HUFAs. The results also suggest thatArtemianauplii and rotifers are capable of readily retroconverting 22:6(n‐3) to 20:5(n‐3) and 22:5(n‐6) to 20:4(n‐6) through the process of β‐oxid

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00614.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractTwo 10‐day hatchery experiments were conducted to evaluate s‐type (Hawaiian strain) and ss‐type (Thailand strain) rotifersBrachionus plicatilisand cryogenically preserved oysterCrassostrea gigastrochophores as first feeds for larval Nassau grouperEpinephelus striatus. Newly hatched grouper larvae were reared at densities of 11.2–20.8/L in 500‐L tanks at 36–38 ppt salinity, 25–26 C, and under a 11‐h light: 13‐h dark photoperiod. Beginning on day 2 posthatching (d2ph), prey were maintained at a density of 20 individuals/mL, while phytoplankton (Nanochloropsis oculata) was maintained at 500 × 103cells/mL. In experiment 1, survival and growth were higher (P<0.05) for fish fed small s‐type rotifers (mean lorica length = 117 μm; fish survival = 7.96%) selected by sieving than for fish fed non‐selected rotifers (mean lorica length = 161 μm; fish survival = 2.13%). These results demonstrated the advantage of small prey size and suggested that super‐small (ss‐type) rotifer strains would be beneficial. In experiment 2, three feeding regimens were compared: 1) ss‐type rotifers (mean lorica length = 147 μm); 2) oyster trochophores (mean diameter = 50 μm) gradually replaced by ss‐type rotifers from d5ph; and 3) a mixed‐prey teatment of 50% oyster trochophores and 50% ss‐type rotifers. Survival was higher (P<0.05) for larvae fed mixed prey (15.6%) than for those fed rotifers (9.73%) or trochophores and rotifers in sequence (2.55%), which also showed the slowest growth. Oyster trochophores, although inadequate when used exclusively, enhanced survival when used in combination with rotifers, possibly by improving size selectivity and dietary quality. In a pilot‐scale trial, larvae were cultured through metamorphosis in two 33.8‐m3outdoor tanks. Fertilized eggs were stocked at a density of 10 eggs/L and larvae were fed ss‐type rotifers from d2ph‐d20ph, newly hatchedArtemiafrom d15ph‐d18ph, 1‐d‐oldArtemianauplii from d18ph‐d62ph. Survival on d62ph was 1.17%, wit

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1996.tb00615.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY