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1.
Abstract. The aim of this research was lo evaluate the effect of density and feeding level (initially 8 or 16kg/m3 and 1·3% or 2% of present biomass respectively) on productive traits, meat composition and water quality output in farmed rainbow trout, Oncorhynchus mykiss (Walbaum). Individual fish growth shows significant differences in relation to density and feeding level; feed conversion rate is positively Influenced by the lower feeding level and low rearing density. At low density, specific growth rate, protein efficiency ratio and coefficient of variation of individual final weights are more favourable than at high density. Dry matter and lipid composition of meat are positively affected by feeding level; whereas no differences are recorded on the amino acid and fatty acid profiles. Water quality shows differences due to density (NO3 and NH4+) and feeding level (NO2, NH4+ and P).  相似文献   

2.
A generalized nitrogen budget was constructed to evaluate the potential role of mangrove sediments as a sink for dissolved inorganic nitrogen (DIN) in shrimp pond effluents. DIN concentrations were measured in pond effluents from three semi-intensive shrimp ponds along the Caribbean coast of Colombia between 1994–1995. Mean NH4+ concentrations in the discharge water for all farms were significantly higher (67 × 12 μg/L) than in the adjacent estuaries (33 × 8 μg/L). Average NH4+ concentrations in the pond discharge over all growout cycles were similar, representing an approximate doubling in relation to estuarine water concentrations. In contrast, NO2-+ NO3- concentrations were similar in both pond effluent and estuarine waters. Dissolved inorganic nitrogen loading of the ponds was similar. The estimated reduction of DIN in pond effluents by preliminary diversion of outflow to mangrove wetlands rather than directly to estuarine waters would be × 190 mg N/m2 per d. Based on this nitrogen loss and depending upon the enrichment rate, between 0.04 to 0.12 ha of mangrove forest is required to completely remove the DIN load from effluents produced by a 1-ha pond.  相似文献   

3.
The effects of heavy metals (Hg2+, Cd2+, Co2+, Cr3+, Pb2+, Cu2+, Fe2+. Ni2+, Zn2+, Mn7+, Mn4+ and Mn2+) on the relative hatching percentage of brine shrimp, Artemia salina were assessed. Artemia salina cysts (San Francisco Bay Brand) hatched in seawater containing various heavy metal concentrations. After 48 hours, the number of hatched nauplii were counted. A negative linear relationship between hatching rate of Ariemia salina cysts and heavy metal concentration occurred, except copper which conformed to a cubic model. The relative toxicities of heavy metals on Artemia salina cysts were as follows (Cu2+, most toxic; Mn2+, least toxic): Cu2+ > Zn2+ > Ni2+ > Co2+ > Mn7+ > Cr3+ > Cd2+ > Fe2+ > Hg2+ > Mn4+ > Pb2+ > Mn2+.  相似文献   

4.
Post-larval and juvenile Macrobrachium rosenbergii were exposed for 72 h at 29 C to four pH levels (8.5, 9.0, 9.5, 10.0) and four concentrations of un-ionized ammonia-nitrogen (0, 1, 2, and 3 mg/L NHj-N). Results indicated potentiation between NH3 and high pH. Juveniles were more tolerant of high pH and NH3 than post-larvae.
For post-larvae, estimates of 72 h LC50 for pH were 9.43, 9.21, and 8.71 at 0, 1, and 2 mg/L NH3-N, respectively; 72 h LC50 estimates for NH3-N were 2.18 and 1.45 mg/L at pH levels of 8.5 and 9.0, respectively. For juveniles, estimates of 72 h LC50 for pH were 9.91, 9.56, 9.04, and 8.76 at 0, 1, 2, and 3 mg/L NH3-N, respectively; 72 h LC50 estimates for NH3-N were 2.02 and 0.54 mg/L at pH 9.0 and 9.5, respectively.
In pond culture of M. rosenbergii , high pH levels can cause mortality at stocking. The 72 h data can be used as an indication of safe stocking levels of pH and ammonia. These data suggest that post-larvae should not be exposed to pH > 9.0 nor to NH3-N > 1 mg/L in the pH range 8.5–9.0 and juveniles should not be exposed to pH > 9.5 nor to NH3-N > 0 mg/L at pH 9.5, > 1 mg/L at pH 9.0, or > 2 mg/L at pH 8.5.  相似文献   

5.
ABSTRACT:   In order to find out the role of sodium bicarbonate (NaHCO3) on the initiation of sperm motility in the Japanese eel Anguilla japonica , interactions were investigated between NaHCO3 and various reagents (K+ channel blocker 4-aminopyridine [4-AP], ammonium chloride [NH4Cl], sodium acetate and calcium chloride [CaCl2]) that could regulate internal factors (intracellular K+, intracellular pH [[pH]i] and intracellular Ca2+) in sperm motility. Contradictory effects of NaHCO3 were observed (i.e. an inhibitory effect when 4-AP was absent and a promoting effect when 4-AP was present). Sodium bicarbonate inhibited the initiation of sperm motility in the Japanese eel. However, NaHCO3 restored the motility of immotile sperm that 4-AP inhibited. The inhibitory effect of NaHCO3 disappeared with the addition of NH4Cl, which raised [pH]i, but the promoting effect was not affected by [pH]i. Although NaHCO3 recovered motility in the presence of 4-AP, this recovery was also observed with the addition of CaCl2 instead of NaHCO3. In the initiation of sperm motility in the Japanese eel, two roles for NaHCO3 are suggested: an inhibitory role relating to the regulation of [pH]i and a promoting role relating to the uptake of another initiation factor, which could be Ca2+.  相似文献   

6.
Tolerance of snakehead Channa striatus to ammonia was tested at three pH levels (8.0, 9.0. and 10.0) in experimental tanks. At pH 8.0, ammonia LC50 estimates for snakehead at 24, 48, 72, and 96 h were >205.7, >203.5, 152.6, and 107.3 mg total ammonianitrogen (TAN)/L (or >10.3, >10.2, 7.6, and 5.4 mg NH3-N/L), respectively. At pH 9.0, ammonia LC50 estimates at 24, 48, 72, and 96 h were >52.4, 62.8, 56.1, 43.4 mg TAN/L (or >18.0, 21.6, 19.3, and 14.9 mg NH3-N/L), respectively. At pH 10.0, ammonia LC50 estimates at 24, 48, 72, and 96 h were 25.7, 21.6, 20.3, and 18.7 mg TAN/L (or 21.6, 18.1, 17.1, and 15.7 mg NH3-N/L). respectively. Our data indicate that the tolerance of snakehead to ammonia was associated with pH. Thus, we recommend that snakehead should not be subjected to prolonged exposures of NH3-N concentration more than 0.54 ma at pH 8.0, more than 1.49 mg/L at pH 9.0, or more than 1.57 mg/L at pH 10.0.  相似文献   

7.
Pcnaeus monodon juveniles (35.4 ± 2.2 mm TL) were exposed to seawater (20 ppt) having different concentrations of total ammonia (NH3+ NH,+) and nitrite. Median lethal concentration (LC50) was determined with static-renewal tests. The LC50, of total ammonia-N, NH3-N and niMte-N on shrimps decreased with increase of exposure time. The 24, 48, 72, % and 120 h LC50 were 94.96, 61.09, 47.47 45.58 and 38.00 mg/L total ammonia-N (2.68, 1.73, 135, 1.29 and 1.08 mg/L NH3-N) and 215.85, 185.33, 88.54, 54.76 and 37.97 mg/L nitrite-N, respectively. The 144h LC50 of total ammonia-N and NH3-N was 36.71 mg/L and 1.04 mgL. The "threshold" of ammonia and nitrite was found at 144h and 120h respectively, from the toxicity curve approaching asymptote. A "safe value" was 3.7 mg/L total ammonia-N, 0.1 mg/L NH3-N (20 ppt, pH 7.70, 27C) and 3.8 mg/L nitrite-N for P. monodon juvenile .  相似文献   

8.
SUMMARY: The effects of nutrient salts eluted from artificial algal reef blocks made with sea-bottom sediment (hedoro) and cement to the growth and survival rate of the gametophytes and juveniles of Eisenia bicyclis were investigated. When each sample block was submerged in filtered seawater for 28 days, the nutrient salt content from the hedoro increased with time and, in particular, the amounts of NO3−− N and NO2−− N reached a constant level on day 10. We observed that the lower the cement ratio, the higher the concentrations of eluted NH4+− N and PO43−− P. The growth of gametophytes as well as juveniles was highest in the elution of the block with the lowest cement ratio of 30%. In contrast, the survival rate of gametophytes and juveniles decreased linearly with time and the survival rate was higher for the hedoro blocks than for the block made of mortar.  相似文献   

9.
Abstract. Ammonia excretion rate of the marine bivalve Tapes decussatus (L.) varied with body weight, temperature and starvation. There was a steady state in the excretion rates, in which these rates neither increased nor decreased during the first 6 days of starvation. The highest rates of ammonia excreted during the steady state (before decline to lower level) depended on the temperature (715 ± 86 and 395 ± 55 μg NH4.N/clam/h × 10−2) at 28°C and 20°C, respectively. At 16°C, the steady state extended from 6h to 18d starvation. Ammonia excretion rates were higher for starved clams than for fed clams at all sizes, e.g. clams of 0·07 g dry flesh weight (28 ± 9 and 13 ± 5 μg NH4.N/clam/h × 10−2 respectively) at 16°C but not at 20°C and 28°C. At each temperature, weight-specific ammonia excretion rates were related to dry flesh weight of starved clams but were not related to fed ones.  相似文献   

10.
This present study was designed to investigate the effects of stocking density and water exchange on the growth rate, survival and performance index of L. setiferus postlarvae under controlled laboratory conditions. The experiment was done with postlarvae (PL10 to PL40) at densities of 50, 150, 250 and 350 shrimp/m2 and various different water exchanges rate per day (0, 6, 12 and 18%). The maximum growth rate was obtained for shrimp with 12% water exchange per day at all densities. A reduction of the maximum growth rate was observed in relation to density with the highest values in shrimp stocked in a density of 50 and 150 shrimp/m2 (mean value of 0.53 mg/d) and the lowest in shrimp stocked in a density of 350 shrimp/m2 (0.24 mg/d). The multiple regression equation obtained to relate performance index (growth rate* survival : PI), shrimp density (X1) and water exchange (X2) was: PI = 0.31 + (0.001) X1+ 0.039 X2+ 2.28 × 10−6 X12+ (−0.0017) X22+ (0.000026)X1X2, R 2= 0.78; P > 0.03. According to this equation the optimum shrimp density-water exchange comhination was between 5 to 12% of water exchange at stocking density of between 50 and 150 shrimp/m2. Salinity, ammonia-N and nitrite-N increased according to the time spent in tanks without water exchange. With no (0%) water exchange, water quality parameters measured were outside the optimum for L. setiferus postlarvae. The use of optimum density and water exchange in a nursery system for L. setiferus with optimum variables established is proposed.  相似文献   

11.
Shipping trials were conducted with adult Penaeus setiferus to determine the effect of 24 hour closed shipments on water quality, to evaluate methods of reducing water quality deterioration and to maximize packing density (biomass). Other trials were undertaken with juvenile P. setiferus and adult P. vannamei for comparison. The method utilized 8 L seawater chilled to 18–19 C, inside doubled polyethylene bags held in a Styrofoam box (42 × 42 × 23 cm deep). Gaseous O2 was injected into the water to 8 ppm (for standardization) and into the space above the water. Super-saturation of dissolved oxygen (>20 ppm for 24 hours) had no adverse effect on survival. Initial trials resulted in increased ammonia (from 0.1 to 4–6 ppm NH4-N), increased carbon dioxide (from <2 to 80–100 ppm), increased temperature (from 18–19 to 25–26 C) and decreased pH (from 8.0 to 6.0–6.4). Increases in shipping density (number or biomass of shrimp per L seawater) further intensified water quality deterioration. Carbon dioxide (with concomitant pH decline) is implicated as the major limiting factor during 24 hour closed shipment. Ammonia accumulation was reduced or totally eliminated with addition of AmQuelΘ (Kordon, Inc, Hayward, California), 2 depending on the dosage used. The buffer, Trizma® 8.3 (Sigma Chemical Co, St. Louis, Missouri), 2 limited CO2 buildup and reduced pH decline. Maintenance of low temperature over 24 hours was enhanced with addition of a frozen cold pack placed over the shipping bags. However, the control of ammonia, pH and carbon dioxide by the addition of AmQuel and Trizma did not increase survival, possibly due to toxic effects of the chemicals.  相似文献   

12.
The composition of sediment pore water was determined for ponds constructed on clayey Ultisols at Auburn, Alabama. Pore water was anaerobic and contained much higher concentrations of ferrous iron (Fe2+), soluble reactive phosphorus (SRP), total phosphorus (TP), total ammonia-nitrogen (TAN), and sulfide (S2−) than surface or bottom waters. Concentrations of SRP and TP in pore water were higher in ponds with high soil phosphorus concentrations than in a new pond with less soil phosphorus. Increased concentrations of organic matter in soil or larger inputs of feed to ponds favored greater microbial activity in soils and higher concentrations of TAN in pore water. The pH of pore water was 6.5–7.0, and pH was apparently controlled by the equilibrium:

Movement of Fe2+, SRP, and S2− from pore water into pond water apparently was prevented by the oxidized layer of soil just below the soil-water interface. Pond managers should concentrate on maintaining this oxidized layer to reduce the tendency for toxic substances to diffuse into the pond water.  相似文献   

13.
Tiger prawn Penaeus monodon postlarvae (PL6) were exposed to a mixture of ammonia and nitrite by the static renewal method. When the toxicity ratio of the ammonia-nitrite mixture was 1:1, the 48 h, 72 h and 96 h LC50 values were 2.20, 1.43 and 0.84 toxicity units which were equivalent to 12.66 mg/L ammonia-N (0.60 mg/L NH3-N) plus 14.91 mg/L nitrite-N, 8.23 mg/L ammonia-N (0.39 mg/L NH3-N) plus 9.69 mg/L nitrite-N, and 4.83 mg/L ammonia-N (0.23 mg/ L NH3-N) plus 5.69 mg/L nitrite-N. When the toxicity ratio of the ammonia-nitrite mixture was 51, the 48 h, 72 h and 96 h LC50 values were 2.50, 1.56 and 0.85 toxicity units which were equivalent to 23.98 mg/L ammonia-N (1.13 mg/L NH3-N) plus 5.65 mg/L nitrite-N; 14.96 mg/L ammonia-N (0.71 mg/L NH3-N) plus 3.52 mg/L nitrite-N, and 8.15 mg/L ammonia-N (0.39 mg/ L NH, N) plus 1.92 mg/L nitrite-N. A mixture of ammonia and nitrite exerted greater toxicity than high concentrations of either ammonia or nitrite alone. The combined effect of ammonia and nitrite on P. monodon postlarvae was antagonistic for 48 and 72 hours exposure, but synergistic after 96 hours exposure.  相似文献   

14.
Abstract. Rainbow trout, Salmo gairdneri Richardson, were reared intensively in nine aerated static-water ponds. Dissolved oxygen concentrations were maintained above 5 mg/l and un-ionized ammonia (NH3) levels were monitored in all ponds. Fish were removed periodically and gill, liver and trunk kidney samples were removed for histological examination. Average NH3 concentrations did not exceed a previously reported chronically toxic level, but average daily maximum concentrations exceeded this level in all but two ponds. Gills exhibited lesions characteristic of those attributed to ammonia exposure in all ponds and fish with the most damaged gills had livers demonstrating reduced glycogen vacuolation. No histological changes were noted in kidney tissue. Because gills were damaged even though average NH3 levels were quite low, it is recommended that research in static water carefully consider the cyclical nature of NH3 concentrations.  相似文献   

15.
Phosphorus fractions in soil and water were determined for a 22-year-old, 400m2 fish pond constructed on clayey Ultisols at Auburn, Alabama. This pond had been used in pond fertilization and fish feeding experiments each year. Total phosphorus concenlrations in bottom soil were greater in deep water than in shallow water areas. Highest concentrations of phosphorus occurred in the 5–10 cm soil layer, but phosphorus had accumulated above its original concentration to depths of 20 to 45 cm ( x = 36.8 cm). The soil phosphorus accumulation rate was 2.68 g/m2 per year. Less than 1% of the total phosphorus in soils from three ponds was extractable in distilled water or 0.5 M NaHCO3. Sequential extraction with 1 M NH4Cl, 0.5 N HCl, and 0.1 N NaOH removed less than 25% of the total phosphorus. The loosely-bound phosphorus fraction (1 M NH4Cl extractable) was 0.4 to 5.2% of the extractable phosphorus. The ability to adsorb phosphorus decreased and the capacity to release phosphorus increased in pond soils as total phosphorus concentration increased. After 22 years of aquacultural production, phosphorus adsorption sites in a pond soil were only about half-saturated. Although soluble phosphorus accounted for 37% of the phosphorus in pond water, only 7% of the total phosphorus in pond water was soluble reactive phosphorus. The phosphorus pool in pond soil was over 500 times greater than that of pond water, but most of the soil phosphorus was strongly adsorbed and unavailable.  相似文献   

16.
The effect of ammonia and pH levels on giant river prawn Macrobrachium rosenbergii larvae were evaluated to provide science-based information on safe levels of ammonia and pH for larviculture. Survival rate, developmental stage, and larval weight gain were determined for larvae kept in water with total ammonia (NH 4-N)concentrations of 0, 1, 2, 4, and 8 mg\L and pH 7, 8, and 9. The trials were conducted in two phases: phase 1, larvae from stages I through VIII and phase 2, larvae from stage VIII until metamorphose. Oxygen consumption was determined for larvae in stages I and VIII at total ammonia concentrations of 0, 4, and 8 mg/L and pH 8. Survival rate up to stage VIII varied from 86 to 98% and did not differ for total ammonia concentrations in pH 7 and 8 and for 0 mg/L NH4 N in pH 9. Survival rate was significantly lower (0–20%) for total ammonia concentrations from 1 to 8 mg/L (0.43–3.41 mg/L of unionized ammonia) in pH 9. Larval stage indexes (7.9–8.0 range) and weight gain (1.572–2.931 mg range) of larvae at the end of phase 1 of the experiment did not differ for the different ammonia concentration solutions, but were significantly lower in pH 9. In phase 2, no parameter differed among treatments for pH 7 and 8; however there was total mortality at pH 9 until 96h. Respiration rates diminished when larvae were exposed to total ammonia concentrations of 4 and 8 mg/L (0.28 and 0.55 mg/L of unionized ammonia), but development remained unaltered. Therefore, M. rosenbergii larvae tolerate high levels of total ammonia, while toxicity depends primarily on unionized ammonia concentrations. In addition, alkaline pH (9) acted directly on the larvae, curbing development and causing severe mortality. Larval tolerance to high ammonia and pH levels decreases for the last zoeal stages.  相似文献   

17.
Abstract – Perch ( Perca fluviatilis ) can act as a piscivore from larval stage VI (body size 10.3 mm) on newly hatched larval roach ( Rutilus rutilus ), bream ( Abramis brama ) and smaller siblings of its own cohort. Consumption rates at this stage were approx. 0.5 prey/perch*h at 21°C. Larval perch predation was strongly gap-limited, and the maximum size of roach consumed by perch (perch length interval 10.3–62.0 mm) under experimental conditions followed the linear regression, Pprey-max.=0.478*LPred.+1.829 ( r 2=0.99, P <0.001, n =12). Under experimental conditions, predatory 0+ perch substantially affected the size distributions of 0+ roach prey cohorts, since smaller prey individuals were predated more frequently than larger ones. In both unimodal and bimodal size distributions of prey roach, the distributions changed according to the maximum prey size consumed by the added predatory perch. Unimodal prey distributions were positively skewed when piscivorous perch were added compared with controls without predators. According to the size distributions of lake-living 0+ roach and 0+ perch and the relative size difference between prey and predator, the vulnerability of 0+ roach cohort to 0+ perch predation changed from June to September. Prey vulnerability was extremely sensitive to the relative size difference between predator and prey. Therefore differences in hatching time and growth rates between the two species will strongly influence the potential for predator-prey interactions. Note  相似文献   

18.
Abstract. Tiger shrimp, Penaeus monodon Fabricius, post-larvae (32·0±3mg, 1·43±0·03 cm) were exposed to control, 0·12, 0·60, 1·20 and 2·40mg/l ammonia-N (un-ionized plus ionized ammonia as nitrogen) which is equivalent to control, 6,32,63 and 126μg/1 NH3-N (un-ionized ammonia as nitrogen) for 8 weeks in 25 ppt, as pH of 7·85–8·18 and 26–28°C by static renewal method. Growth in weight and length of the shrimps exposed to 1·20 and 2·40 mg/l ammonia-N were significantly lower (P < 0·05) than those exposed to control. The EC50 (concentration that reduced growth by 50% of that of the controls) was 1·33 mg/l ammonia-N, 70 μg/l NH3-N for weight gain, and 2·35 mg/1 ammonia-N, 123μg/l NH3-N for length gain of P. monodon post-larvae. The'maximum acceptable toxicant concentration'(MATC) of ammonia-N and NH3-N for P. monodon post-larvae was 0·60mg/l and 32μg/l, respectively after 6 weeks of exposure.  相似文献   

19.
SUMMARY: The effectiveness of in vitro embryo culture of the giant freshwater prawn Macrobrachium rosenbergii depended on the age of the embryos at the onset of culture and on the concentrations of various compositions in the medium. Embryos that started being cultured on day 0.5 after oviposition were more sensitive to variations in the medium compositions than those that started being cultured on day 10.5 after oviposition. An optimal NaCl level was essential for embryonic development, survival, hatching and survival of the newly hatched larvae. Variations of NaCl or KCl levels dramatically altered embryonic development, and variation of the MgCl2 + MgSO4 level significantly lowered survival of the embryos that started being cultured at the early stage of development. In contrast, no significant change in embryonic development was observed upon variation of the CaCl2 level. Hatching of the embryos required the presence of NaCl and CaCl2 but not KCl or MgCl2 + MgSO4. The ionic requirements of the newly hatched larvae differed from that of the developing embryos. Variations of NaCl, KCl or CaCl2 but not MgCl2 + MgSO4 levels significantly influenced the survival of the newly hatched larvae.  相似文献   

20.
The objective of this experiment was to test the efficacy of a probiotic (Efinol®L) during transportation of marbled hatchetfish, Carnegiella strigata . Wild specimens were captured from a small stream and transported for 24 h in plastic fish boxes with a probiotic (10 mg L−1) and probiotic-free water. The boxes were sampled at 3, 12 and 24 h of transport. At the end of the experiment, the survival rate was close to 100% in both treatments. Dissolved oxygen diminished with time in both treatments, but the probiotic group had significantly higher levels. Conductivity, pH and ammonia increased significantly during the transport, demonstrating higher levels in the probiotic-free group. Fish from both treatments presented very high net Na+ and K+ effluxes after 3 h of transport. At 24 h, net K+ effluxes in fish of the probiotic treatment reached values close to zero and a significantly lower Na+ efflux was observed. Cortisol levels in both treatments at 3 and 12 h were significantly higher than that in control samples. Higher body cortisol levels were observed in the probiotic-free group than that in the probiotic group at 3 and 12 h. The results demonstrate that addition of a probiotic during fish transport improves water quality and leads to fish presenting a lower stress response intensity.  相似文献   

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