Capture versus tagging impacts on chum salmon freshwater spawning migration travel times

The spawning migration travel times of chum salmon, Oncorhynchus keta (Walbaum), fitted with gastrically implanted radio tags vs external spaghetti tags were tested for a short [≈60 river km (rkm)] and long migration route (≈730 rkm) on the Koyukuk River, Alaska, USA. Using a novel application of statistical arrival curve models to infer travel times for uncaptured fish, migrations by chum salmon not directly handled during the study were also assessed. Results demonstrated negligible differences in travel times within migration routes between fish fitted only with spaghetti tags and fish fitted with radio tags, indicating low impacts on migration travel behaviour associated with gastric tags once deployed. Conversely, travel times for unhandled fish as inferred by statistical arrival models may have been 12%–24% shorter than those for fish captured with gillnets for tagging. These results suggest that, if present, chum salmon migration behaviour impacts may be more strongly associated with fish capture than tag deployment.     

Fish assemblage dynamics in an intermittent river of the northern Australian wet–dry tropics

Intermittent rivers make up a large portion of the global river network and are the dominant river type in northern Australia. Increased pressure is being placed on such systems, and a better understanding of their ecology is needed. We examined, over a 7‐year period, the fish fauna of the intermittent Fergusson River, a major tributary of the Daly River of the northern Australia. Changes in habitat structure with the onset of the dry season involved contraction of the riffle/run/pool habitat to a single refugial pool, the size of which was determined by antecedent wet season hydrology. The fishes present comprised a subset of species present within the Daly River main channel and consisted of the most widely distributed of northern Australia's freshwater fishes. The Fergusson River provides suitable spawning habitat for species during the wet season (e.g. Hephaestus fuliginosus, Leiopotherapon unicolor and Neosilurus catfishes) and during the dry season for a different set of species (e.g. Amniataba percoides, Melanotaenia australis and Glossogobius aureus). Little year‐to‐year variation in assemblage structure was observed early in the dry season, whereas interannual variation in late dry season assemblages was substantial. Dry season recruitment imparted some of the interannual variability in assemblage structure recorded between late dry season samples. Piscivorous fishes were an important, but temporally variable, component of the assemblage present in the late dry season refugial habitat, and predation was potentially another important source of variation in assemblage structure.     

Treatment of sustained monomorphic narrow‐complex ventricular tachycardia in a 16‐year‐old Arab mare with a constant rate of infusion of lidocaine and oral propranolol

A 16‐year‐old Arab mare was referred for treatment of a tachydysrhythmia detected on electrocardiogram by the referring veterinarian. Monomorphic, narrow‐complex ventricular tachycardia (VT) was confirmed by electro‐cardiogram in a normal base‐apex configuration. Subsequent diagnostic testing, including echocardiography and measurement of plasma cardiac troponin concentration, did not reveal a definitive cause for the dysrhythmia. Conversion of VT to ventricular bigeminy occurred following treatment with magnesium sulfate and lidocaine hydrochloride, administered intravenously. Treatment with orally administered propranolol subsequently led to conversion to sinus rhythm with intermittent ventricular premature complexes (VPCs). Oral prednisolone treatment was also initiated to address the possibility that VT resulted from underlying myocarditis. The mare was discharged with oral propranolol, a tapering course of prednisolone, and exercise restriction. Follow‐up cardiac examination 6 weeks later revealed persistent, intermittent VPCs and reversion to VT occurred during exercise. Sinus rhythm with intermittent VPCs was re‐established following the administration of lidocaine. The mare was again discharged with oral propranolol therapy, which was subsequently replaced with oral sotalol. Sudden death occurred 4 weeks later but a post mortem examination was not performed.     

Contemporary Flux of Radionuclides to Contaminated Saltmarshes in the Esk Estuary,Cumbria

The Esk estuary is approximately 10 km from the marine outfall fromBritish Nuclear Fuels plc (BNFL) Sellafield Site and saltmarshes here havereceived significant quantities of radionuclides as reported in many studiessince 1975. These studies have concentrated on the inventory ofradionuclides in the estuary, but they have not addressed the continualreworking of radionuclides from these deposits. A detailed investigation ofboth the concentration of ¹³⁷Cs in the surface 10 cm and gammaair-kerma dose rates has been made where 120 determinations were made in agrid over 14600 m² of saltmarsh. The surface microtopographyis shown to be important for the continuing deposition of contaminatedsediments to the saltmarsh surface. This study has concentrated on thedevelopment and the possible application of sediment traps made fromAstroturf (an artificial grass). They were deployed at three sites whichwere representative of the major saltmarsh units in the estuary. The trapswere used to investigate the mobile sediments during a single tide, for aweek, and for a month. The Astroturf provided a reasonable analogue for thesaltmarsh surface and was arranged such that the radionuclide concentrationof the trapped sediment was measured directly by gamma spectrometry. Sediment deposition rates of between 30 and 240 g m^-2d^-1 were determined for the study sites, and these wereconsistent with earlier studies. Measurement of the radionuclideconcentration of the deposited sediment showed the addition of between 90and 750 Bq ³¹⁷Cs m^-2 d^-1 and 200and 1400 Bq ²⁴¹Am m^-2 d-1. At thedepositional sites over the saltmarsh this would represent an annualaddition of about 90 kBq m^-2 of ¹³⁷Cs and 180kBq m^-2 of ²⁴¹Am.     

Fullerene pipes

Single-wall fullerene nanotubes were converted from nearly endless, highly tangled ropes into short, open-ended pipes that behave as individual macromolecules. Raw nanotube material was purified in large batches, and the ropes were cut into 100- to 300-nanometer lengths. The resulting pieces formed a stable colloidal suspension in water with the help of surfactants. These suspensions permit a variety of manipulations, such as sorting by length, derivatization, and tethering to gold surfaces.     

The hydrological basis for conservation of floodplain wetlands: implications of work at Narborough Bog,UK

1. Increasing concern for the environmental consequences of wetland loss has yet to be reflected in a wider application of hydrological techniques for their preservation. This paper looks at the specific example of floodplain wetlands by first considering how local hydrogeomorphological conditions may explain varied wetland occurrence. The effects of variations in individual hydrological fluxes are identified and the ability of standard hydrological monitoring programmes to represent these processes is considered. 2. These concepts are illustrated with reference to work on Narborough Bog, a small floodplain wetland in the UK. The characteristics of the wetland are outlined to illustrate how this determined the design of a monitoring programme investigating wetland hydrology and the practicalities of conservation. Measurements of water-table height were completed using a network of 30 piezometers located in the wetland and with additional measurements of river stage and meteorological variables. 3. The results of this data collection programme over the period 1991–1993 are described. The value of the data in characterizing the hydrology of the wetland is assessed and the need for sustained monitoring of variations in wetland water storage and flux is emphasized. The implications of the results for future wetland monitoring programmes are identified. 4. Hydrological data collected in this way can be used to develop a wetland mathematical model. This may be achieved by aggregating wetland sedimentological characteristics and by modelling specific periods of precipitation and evapotranspiration to determine the validity of the modelling process. Current shortcomings in the modelling process are discussed; however, wider application of this technique might help direct informed conservation of floodplain wetland landforms through improved understanding of the balance between internal and external water fluxes and their interrelationships. Similarly, models enable evaluation of the impacts of future catchment changes on wetlands. © 1997 John Wiley & Sons, Ltd.     

Vertebrate mucus stimulates biofilm development and upregulates iron acquisition genes in Flavobacterium columnare

Columnaris disease is responsible for substantial losses throughout the production of many freshwater fish species. One of the ways in which the bacterium Flavobacterium columnare is so effective in initiating disease is through the formation of biofilms on fish skin and gills. To further explore the interaction between host factors and bacterial cells, we assayed the ability of vertebrate mucus to enhance F. columnare biofilm development. Different concentrations of catfish, tilapia and pig mucus (5–60 µg/ml) increased biofilm growth at varying degrees among F. columnare isolates. Our data suggest that vertebrate mucus acts as a signalling molecule for the development of F. columnare biofilms; however, there are clear disparities in how individual isolates respond to different mucus fractions to stimulate biofilms. The expression of iron acquisition genes among two genomovar II isolates showed that ferroxidase, TonB receptor and the siderophore synthetase gene were all significantly upregulated among F. columnare biofilms. Interestingly, the siderophore acetyltransferase gene was only shown to be significantly upregulated in one of the genomovar II isolates. This work provides insight into our understanding of the interaction between F. columnare and vertebrate mucus, which likely contributes to the growth of planktonic cells and the transition into biofilms.