Assessing the abundance and distribution of eggs of sardine, Sardinops sagax, and round herring, Etrumeus whiteheadi, on the western Agulhas Bank, South Africa, using a continuous, underway fish egg sampler

A continuous, underway fish egg sampler (CUFES) was employed to assess the abundance and distribution of eggs of both sardine, Sardinops sagax , and round herring, Etrumeus whiteheadi , on the Western Agulhas Bank, South Africa, during September 1996. Samples were collected while underway along six inshore/offshore transects, and at stations along the transects. Volumetric estimates of egg density (eggs m⁻³) from on-station CUFES samples were highly correlated with both volumetric and areal (eggs m⁻²) estimates of egg density from samples collected from CalVET net hauls at these stations, demonstrating the validity of this novel sampling technique. Sardine and round herring eggs were encountered in a band running parallel to the coast and extending from 10 to 30 nautical miles offshore to the shelf edge, and highest egg densities were associated with strong north-west-flowing currents in the region of the shelf edge. Collecting samples while underway increased the precision of the estimate of mean egg density for sardine eggs but not for round herring eggs. The use of CUFES in obtaining a fine-scale resolution of sardine egg distribution, and as a tool for stock assessment, are discussed.     

Remotely sensed spawning habitat of Pacific sardine (Sardinops sagax) and Northern anchovy (Engraulis mordax) within the California Current

We use trivariate kernel density estimation to define spawning habitat of northern anchovy ( Engraulis mordax ) and Pacific sardine ( Sardinops sagax ) in the California Current using satellite data and in situ egg samples from the Continuous Underway Fish Egg Sampler (CUFES) deployed during surveys in April by the California Cooperative Oceanic Fisheries Investigations (CalCOFI). Observed egg distributions were compared with monthly composite satellite sea surface temperature (SST) and surface chlorophyll a (chl a ) data. Based on the preferred spawning habitat, as defined in SST and chl a space, the satellite data were used to predict potential spawning habitat along two areas of the west coast of North America. Data from the southern area (21.5 to 39°N) were compared to observations from the CUFES data for the period 1998–2005. Northern anchovy and Pacific sardine exhibited distinctly different spawning habitat distributions. A significant relationship was found between satellite-based spawning area and that measured during surveys for sardine. CUFES area estimated for sardine was similar in magnitude to that estimated from satellite data (∼60 000 km²). In contrast, spawning habitat of anchovy averaged between 1000 and 200 000 km² for the period 1998–2005, for CUFES and satellite estimates, respectively. Interannual variability in the area (km²) and duration (months) of estimates of suitable habitat varied between species and between the northern (39 to 50.5°N) and southern portions of the California Current. Long-term monitoring of habitat variability using remote sensing data is possible in the southern portion of the California Current, and could be improved upon in the northern area with the addition of surveys better timed to describe relationships between observed and estimated spawning habitats.     

Selenium nutrition of hybrid striped bass (Morone chrysops × M. saxatilis) bioavailability, toxicity and interaction with vitamin E

Two concurrent 12-week feeding trials were conducted to evaluate the bioavailability of inorganic sodium selenite and organic seleno-DL-methionine and to investigate the potential interaction between selenium and vitamin E in juvenile hybrid striped bass. In experiment 1, purified diets utilizing casein, gelatin and an amino acid premix as protein sources with a basal selenium concentration of 0.11 mg Se   kg⁻¹ were supplemented with either Na₂SeO₃ to provide selenium concentrations of 1.19, 2.00, 5.17 and 21.23 mg Se kg⁻¹ or with seleno-DL-methionine to provide 0.90, 1.26 and 2.55 mg Se kg⁻¹ and fed to juvenile hybrid striped bass in aquaria. A second experiment evaluated potential interactions by feeding these purified diets with or without supplemental vitamin E or sodium selenite, singularly or in combination. No overt selenium deficiency signs were exhibited by fish in either of the experiments; however, signs of selenium toxicity including retarded weight gain (WG), reduced feed intake and feed efficiency ratio (FER) as well as increased mortality, were observed in fish fed the diet containing more than 20 mg Se kg⁻¹. Whole-body selenium and whole-body selenium retention were linearly influenced by sodium selenite and selenomethionine. However, there was no significant effect of dietary selenium, vitamin E or their interaction on WG, FER and survival. Slope-ratio analysis showed that bioavailability of seleno-DL-methionine as a selenium source for juvenile hybrid striped bass was significantly ( P  < 0.01) higher (3.3-fold) than sodium selenite.     

Comparing river basins world-wide and contrasting inland fisheries in Africa and Central Amazonia

An analysis of covariance relating basin area ( A , km²) to river length ( L , km) and discharge rate ( D , m³ s^–1) was performed for two continents and showed that the two covariates ( L and D ) were highly significant and that the strength of the relationship changed between continents. For comparison, D was excluded but the result remained the same. Although geomorphological models are useful for establishing global levels of production, these regressions should be applied with caution. Historically, simple statistical models were developed to predict fish catches in rivers. These, based upon regression of catches on channel length or basin area for Africa and Central Amazonia, are contrasted in this paper because of their generally similar approach.     

Responses to Pathogen-induced Disturbance: Decomposition, Nutrient Availability, and Tree Vigour

In the Oregon subalpine zone, extensive dieback occurs in relativelypure stands of 150 to 250-year-old mountain hemlock growingon very infertile soils. Tree death is caused by a root-rotfungus, Phellinus weirii. Young trees that become establishedfollowing death of the original forest are apparently not reinfectedby the pathogen until 80–140 years later. whereon mortalityoccurs again. We examined the effects.of this natural disturbanceand subsequent regrowth on a number of ecosystem characteristics. Decomposition rates and nitrogen availability measured by insitu exchange resins increased in the zones of young regrowth,but dropped to values common for old growth as the forest agedand the canopy closed. Phosphorus and potassium accumulationon exchange resins showed trends opposite to nitrogen, and mayhave been associated with changes in biomass. Increased nitrogenconcentrations and decreased lignin concentrations in fine rootsin the zone of young regrowth suggested improved tree nutritionunder conditions of higher N availability and lower leaf areaindex. Tree vigour, estimated as wood production per unit leafarea, also was significantly increased in the zones where youngforests grew. Circumstantial evidence suggests that increasesin nutrient availability and light following death of the matureforest improved photosynthesis leading to increased resistanceof young trees against infection by the pathogen.     

Antimicrobial prophylaxis in canine surgery

In 1961, Burke showed that antibiotics affect primary wound infections favourably only if they are administered before or shortly after bacterial contamination. The effect is optimal if there is already an effective tissue concentration at the time of contamination. During surgery the animal's resistance is strongly reduced, and consequently an infection may be caused by an inoculum present in a rather low concentration, at least lower than in normal circumstances. This reduced resistance lasts until only a few hours after operation. Prophylactic use of antibiotics therefore needs to be continued only for a short time after the final stage of the operation. A great number of clinical trials in human surgery have shown that short term peri-operative prophylactic use of antibiotics causes a reduction in the incidence of post-operative septic complications, in certain categories of operations and in selected groups of patients. Until properly designed, prospective, randomized and controlled clinical trials have been done in small animal clinics, it seems sensible to apply the abundant results from research with experimental animals and from clinical trials in human medicine to small animal surgery. Prophylactic use of antibiotics is indicated if the infection risks or dangers of possible complications are greater than the disadvantages of regular use of antibiotics. The risk factors in the development of wound infections and the choice of antibiotics are discussed.     

Time scales and heterogeneous structure in geodynamic earth models

Computer models of mantle convection constrained by the history of Cenozoic and Mesozoic plate motions explain some deep-mantle structural heterogeneity imaged by seismic tomography, especially those related to subduction. They also reveal a 150-million-year time scale for generating thermal heterogeneity in the mantle, comparable to the record of plate motion reconstructions, so that the problem of unknown initial conditions can be overcome. The pattern of lowermost mantle structure at the core-mantle boundary is controlled by subduction history, although seismic tomography reveals intense large-scale hot (low-velocity) upwelling features not explicitly predicted by the models.     

Functional and morphological studies on blood platelets in a thrombasthenic horse

A four-year-old Standardbred gelding presented with a 3.5 year history of intermittent epistaxis and spontaneous submucosal petechiae and ecchymoses in the nares and the mouth. Routine haematological and biochemical examinations were unremarkable. A thrombocytopathy was suspected when activated partial thromboplastin time, one stage prothrombin time, plasma fibrinogen and the platelet count were all normal. The patient's platelets failed to aggregate with serotonin, adenosine diphosphate, collagen (at 20 micrograms/ml) or the endoperoxide analogue U46619. Very high levels of collagen (100 micrograms/ml) did cause aggregation. The response to the calcium ionophore A23187 was reduced and although complete degranulation occurred the resulting aggregates were unstable. Thromboxane generation in response to collagen and ADP was inferred from the concentration of its stable metabolite thromboxane B2 and was reduced. A diagnosis of a thrombasthenia-like syndrome possibly equivalent to Type II Glanzmann's thrombasthenia in people was made.