Water use and conservation for inland aquaculture ponds

The general hydrological equation, inflow = outflow ± change in storage, can be used to make accurate estimates of water use by ponds for inland aquaculture projects. The primary inflows are precipitation, runoff and regulated water additions. The main outflows are evaporation, seepage, overflow after storms and intentional discharge. Water conservation measures such as maintaining storage capacity in ponds equal to the normal, maximum daily precipitation, reduction in seepage beneath dams and through pond bottoms, fish harvest without draining ponds, and water re-use are discussed. Even with the implementation of water conservation measures, pond aquaculture is a water- intensive endeavour which consumes more water per unit of area than irrigated agriculture. However, the value of aquacultural production per unit of water used greatly exceeds that of irrigated agriculture. Reduction in effluent volume is the most effective water saving means, and not only reduces water consumption but also reduces the pollution potential of pond aquaculture.     

Feasibility of measuring dissolved carbon dioxide based on head space partial pressures

We describe an instrument prototype that measures dissolved carbon dioxide (DC) without need for standard wetted probe membranes or titration. DC is calculated using Henry’s Law, water temperature, and the steady-state partial pressure of carbon dioxide that develops within the instrument’s vertical gas–liquid contacting chamber. Gas-phase partial pressures were determined with either an infrared detector (ID) or by measuring voltage developed by a pH electrode immersed in an isolated sodium carbonate solution (SC) sparged with recirculated head space gas. Calculated DC concentrations were compared with those obtained by titration over a range of DC (2, 4, 8, 12, 16, 20, 24, and 28 mg/l), total alkalinity (35, 120, and 250 mg/l as CaCO₃), total dissolved gas pressure (−178 to 120 mmHg), and dissolved oxygen concentrations (7, 14, and 18 mg/l). Statistically significant (P<0.001) correlations were established between head space (ID) and titrimetrically determined DC concentrations (R²=0.987–0.999, N=96). Millivolt and titrimetric values from the SC solution tests were also correlated (P<0.001, R²=0.997, N=16). The absolute and relative error associated with the use of the ID and SC solution averaged 0.9 mg/l DC and 7.0% and 0.6 mg/l DC and 9.6%, respectively. The precision of DC estimates established in a second test series was good; coefficients of variation (100(SD/mean)) for the head space (ID) and titration analyses were 0.99% and 1.7%. Precision of the SC solution method was 1.3%. In a third test series, a single ID was coupled with four replicate head space units so as to permit sequential monitoring (15 min intervals) of a common water source. Here, appropriate gas samples were secured using a series of solenoid valves (1.6 mm bore) activated by a time-based controller. This system configuration reduced the capital cost per sample site from US$ 2695 to 876. Absolute error averaged 2.9, 3.1, 3.7, and 2.7 mg/l for replicates 1–4 (N=36) during a 21-day test period (DC range, 36–40 mg/l). The ID meter was then modified so as to provide for DO as well as DC measurements across components of an intensive fish production system.     

Chemistry of Sediment Pore Water in Aquaculture Ponds Built on Clayey Ultisols at Auburn, Alabama

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.     

Texture and chemical composition of soils from shrimp ponds near Choluteca, Honduras

Analyses of bottom soils from three recently-established (newer) and three older ponds on each of two, semi-intensive shrimp farms near Choluteca, Honduras, revealed that the 0 to 2.5 cm layer had greater concentrations of most variables than deeper layers. Concentrations of total carbon, nitrogen, sulphur, phosphorus, calcium, iron, manganese, and zinc were greater in older than in newer ponds on one or the other of the farms. After 8–11 y of continuous production, total carbon concentrations varied over pond bottoms, and concentrations usually were greatest (1.5–2.5%) in inlet sections. Nitrogen concentrations were about 20% those of carbon and changes in nitrogen concentration closely followed those of carbon. Precipitation of iron pyrite (FeS₂) in anaerobic soil layers was the apparent cause of sulphur accumulation in older ponds. Phosphorus accumulated in older ponds on the farm where heavy doses of fertilizer were applied. Soils of both older and newer ponds on both farms had large accumulations of major cations, a large portion of which were water-soluble salts. There was no evidence of development of adverse soil quality in older ponds.     

Pond Bottom Management at Commercial Shrimp Farms in Chantaburi Province,Thailand

Most shrimp farmers in Chantaburi Province, Thailand, use water jets to dislodge sediment from empty pond bottoms, and wastewater is held for sedimentation before discharge into natural waters. Other pond bottom management practices used by a few farmers are sediment excavation, leave sediment but till entire pond bottom, and no mechanical treatment. All four methods of pond bottom treatment are followed by sun drying for 30 d. Soil organic carbon concentration in ponds following dry‐out seldom exceeded 2%. Although shrimp production in 24 ponds supplied by the same source of water was negatively correlated with increasing soil organic carbon concentration (r = ?0.582), this observation does not confirm a causative relationship. Moreover, in trials conducted at Burapha University, Chantaburi Campus, bottom soil organic matter concentration following dry‐out differed little irrespective of treatment method. Lower soil moisture concentration revealed that dry‐out was more complete with sediment removal than without, but better dry‐out resulted in lower soil pH. Removal of sediment by excavation or flushing is expensive, and natural dry‐out combined with liming and occasional sediment removal should be investigated as a less expensive and more environment‐friendly alternative to removing sediment after each crop.     

Seasonal variations in the radiation regime within an oak-hickory forest

Seasonal variations in solar elevation, canopy phenology and leaf pigmentation result in a dynamic variation in the radiation regime within a deciduous forest. Measurements of several insolation components taken within an east Tennessee oak-hickory forest during eight combinations of season and phenological conditions of the canopy are presented. Insolation measurements were made with instruments mounted on a moving tram system at seven levels within, and at one level above the canopy.The attenuation of solar radiation is least during the leafless phenoseason since only woody biomass is present to intercept and absorb it. Net radiation is attenuated to a greater extent than shortwave and photosynthetically active radiation, which are attenuated to a similar degree, since the sparse woody biomass does not effectively trap the outgoing reflected and radiated radiation. Solar elevation did not influence the attenuation of insolation within the leafless forest under the conditions studied.The attenuation of insolation within the leafing, spring canopy increases progressively with increasing leaf area. The attenuation among the components, however, varies. Shortwave attenuation progresses at a faster rate with expanding leaf area than photosynthetically active radiation since newly expanded leaves are low in chlorophyll. The penetration of light into the leafing canopy is independent of solar elevations less than 40° and increases linearly with greater solar elevations.The radiation regime within the fully-leafed canopy is rather static. For daily mean values, no effects of leaf age or seasonal variation in solar elevation are evident. Penetration of light into the canopy, however, increases when solar elevation exceeds 65°.The attenuation of insolation components diminishes during the autumnal senescence—abscission phenoseason, in response to changes in leaf pigment and loss of foliage. Attenuation of insolation is greater in the autumn than during spring periods with similar leaf area since the sun is lower in the sky in the autumn.The depletion of photosynthetically active radiation with depth is minimal during the leafless, early leafing and autumnal phenoseasons. Moderate depletion occurs during the late leafing period and maximal depletion occurs during the fully-leafed phenoseason.     

Renal biopsy in the normal cat: examination of the effects of repeated needle biopsy

Three healthy cats were subjected to percutaneous renal biopsy of the left kidney on three occasions at monthly intervals. Three other cats were subjected to three consecutive biopsy attempts on one occasion using the left kidney. Thereafter the six cats were monitored clinically and by means of laboratory analyses of blood and urine until euthanasia four weeks after the last biopsy. Cautious insertion of the biopsy needle in an attempt to avoid over penetration of the kidney resulted in failure to obtain renal tissue on six occasions but in all 12 specimens which did contain renal tissue, glomeruli were present. Major blood vessels were present in two biopsy specimens. At necropsy, radiographic and histological studies demonstrated renal parenchymal and vascular changes in the biopsied kidneys which were similar to but less severe than those produced by a single biopsy attempt. This confirmed that avoidance of damage to major renal vessels is important and suggested that, with care, repeated biopsies need be no more harmful to the kidney than a single biopsy.     

Effects of natural mating stimuli on serum luteinizing hormone, testosterone and estradiol-17 beta in yearling beef bulls

The objective of this study was to determine the effect of natural mating stimuli on serum concentrations of LH, testosterone (T) and estradiol-17 beta (E2) in beef bulls. Twenty sexually experienced, yearling beef bulls were bled every 15 min during a 9-h period, 4 h before and 5 h after exposure to estrual females. For exposure, each bull was placed individually in an isolated pen with two restrained estrual heifers for 10 min or until one service was achieved. Timing and number of all behavioral events, including flehmen responses, abortive mounts and services, were recorded for each bull by two independent observers. Of the 20 bulls, 9 bulls mounted and were removed immediately after achieving a service, 8 bulls mounted without achieving a service and 3 bulls exhibited no interest during exposure. Twelve bulls achieved fewer than three and eight bulls achieved three or more flehmen responses during exposure. Postexposure responses in LH, T and E2 were not consistently correlated with number of mounts or presence or absence of a service. However, postexposure LH and T, but not E2, responses were highly correlated with number of flehmen responses achieved (r = .40 to .66; P = .08 to .001). In bulls that achieved three or more flehmen responses, serum LH increased within 30 min after exposure (P = .02) and serum T was increased dramatically within 1 h after exposure (P less than .01), compared with preexposure hormone concentrations, regardless of the number of mounts and regardless of the presence or absence of a service. Natural mating stimuli had no effect on serum E2, and mounting activity alone and mounting that culminated in a service did not necessarily result in increased LH or T in beef bulls. However, number of flehmen responses achieved during exposure to females dramatically influenced postexposure serum LH and T concentrations in beef bulls.     

Serum and urine concentrations of trypsinogen-activation peptide as markers for acute pancreatitis in cats

The purpose of this study was to compare the clinical utility of the serum concentration of feline trypsin-like immunoreactivity (fTLI), the plasma and urine concentrations of trypsinogen-activation peptide (TAP), and the ratio of the urine TAP and creatinine concentrations (TAP:Cr) in the diagnosis of feline acute pancreatitis. We used 13 healthy cats and 10 cats with a diagnosis of acute pancreatitis. The mean serum fTLI and plasma TAP concentrations were significantly higher in the cats with acute pancreatitis than in the healthy cats (P < 0.05); the mean urine TAP concentrations and the median urine TAP:Cr ratios were not significantly different. Among the cats examined in this study, there was no benefit of plasma TAP over serum fTLI in the evaluation of suspected acute pancreatitis.