The Fraser River plume: some preliminary observations on the distribution of juvenile salmon, herring, and their prey

Zooplankton and fish densities in the southern Strait of Georgia were observed to coincide with variations in surface salinities resulting from the outflow of the Fraser River. Vertical net hauls in the euphotic zone revealed that copepods, amphipods, and euphausiids were significantly more abundant per m³ in the brackish estuarine plume (surface salinities - 10–15 ppt) when compared to the area covered by the freshwater of the Fraser River plume (0–10 ppt) and the region of the Strait of Georgia (25–30 ppt) unaffected by the outflow of the Fraser River.
The estuarine and riverine plumes had significantly higher fish densities (adult and juvenile herring, and juvenile salmonids [excluding chinook]) than the Strait of Georgia region, with no significant differences in densities of juvenile chinook salmon observed between regions. The highest catches of juvenile salmonids were at the boundary between the estuarine plume and the Strait of Georgia. Zooplankton found in the stomach contents of both adult and juvenile herring suggested that the herring were filter-feeding on the zooplankton in the estuarine plume. Juvenile salmonids fed primarily on small unidentifiable juvenile fish. The existence of increased densities of prey items in the estuarine plume is proposed to be the primary mechanism resulting in increased residence time in this region by outmigrating juvenile salmonids. Utilization of aggregated zooplankton could lead to increased salmonid growth rates and therefore to enhanced survival of individuals utilizing the Fraser River plume environment.     

Transfer of chlortetracycline from contaminated feedingstuff to cows' milk

Three groups of four Friesian cows in mid-lactation were fed a compound feedingstuff contaminated with 2, 10 or 300 mg chlortetracycline/kg for 21 days, and were then fed an uncontaminated diet for seven days. A fourth group of four cows was fed an uncontaminated diet throughout the study. Daily pooled milk samples from each cow were analysed by high performance liquid chromatography (HPLC) with a detection limit of 50 microg chlortetracycline/litre. Chlortetracycline was detected in only two milk samples taken from one of the animals fed feed containing 300 mg 300 mg chlortetracycline/kg, and both contained less than the maximum residue limit (MRL) specified by the European Union (100 microg/litre). All the milk samples were also analysed by the Delvotest SP microbiological assay, which has a detection limit of 300 microg chlortetracycline/litre. During the treatment period, this method gave four presumptive false-positive results, because they were not confirmed by HPLC. Selected daily pooled samples from each treatment group were also analysed by the semi-quantitative Charm II radioreceptor assay with a detection limit of 10 microg chlortetracycline/litre. Immunoreactive chlortetracycline was detected only in the animals fed feed containing 300 mg chlortetracycline/kg and several of the results exceeded the EU MRL during the treatment period. No significant treatment effects on animal performance were observed. However, there was a trend towards a higher milk fat concentration (P<0.09) and a lower milk protein concentration (P<0.07) with increasing concentration of chlortetracycline in the diet.     

Association of Pythium coloratum and Pythium sulcatum with cavity spot disease of carrots in Western Australia

All 170 Pythium isolates from carrot cavity spot lesions from a field in Western Australia were found to belong to either P. coloratum or P. sulcatum . All isolates of P. coloratum produced large, brownish-black, water-soaked and depressed lesions on mature carrots inoculated with agar plugs colonized by the pathogen. In comparison, only a few isolates of P. sulcatum produced lesions and these were small. In glasshouse trials, P. coloratum produced substantial and numerous lesions at an inoculum density of 0.5% (weight of millet seed-based inoculum/weight of soil), whilst P. sulcatum produced few and small lesions at inoculum densities of 0.8 and 1% and none at 0.5%. This is the first record of P. coloratum as a causal agent of cavity spot of carrots.     

The early development of disease caused by Phytophthora cinnamomi in Eucalyptus marginata and Eucalyptus calophylla grooving in rehabilitated bauxite mined areas

The soil-borne plant pathogen Phytophthora cinnamomi is widely distributed in the jarrah ( Eucalyptus marginata ) forest of Western Australia. Infested areas of the forest are mined for bauxite and the presence of the pathogen could after the survival of trees re-established after mining. Monitoring of 21 revegetated bauxite mined areas found that survival of jarrah and marri ( Eucalyptus calophylla ) trees was high (85–92% and 93–99%, respectively) after 5–7 years but P. cinnamomi was recovered from dead trees. To identify trees for more detailed study, plant symptoms of stress such as suppressed growth, wilting, yellowing of crown, coppice and epicormic growth and visible stem lesions were used. Over a period of 15 months, 30 E. marginata and 28 E. calophylla were carefully excavated and examined for lesions and the presence of P. cinnamomi. P. cinnamomi was consistently isolated from the lignotuber and collar regions of both hosts but never from the roots alone, except in one instance from E. calophylla where it was isolated from a non-lesioned root. In E. calophylla , the lignotuber appears to be very susceptible to invasion by P. cinnamomi in contrast to the roots which appear resistant. The invasion of the pathogen into the lignotuber and collar regions of both species was consistently associated with ponding of water around the plants. This ponding persists for many hours to days after rain and appears to provide an infection court for P. cinnamomi. Development of rehabilitation procedures to reduce this ponding will minimize the risk of tree deaths caused by this pathogen.     

The ability of Phytophthora cinnamomi to infect through unwounded and wounded periderm tissue of Eucalyptus matginata

Unwounded and wounded periderm tissue of 1-year old stems of Eucalyptus marginata were infected and lesioned after 5 days'exposure to either mycelium or motile zoospores of Phytophthora cinnamomi. Lesions produced by P. cinnamomi were longer in wounded than in unwounded stems. The inclusion of non-sterile mine site soil with inocula in the unwounded treatments did not affect the rate or extent to which P. cinnamomi colonized E. marginata stem tissue. The ability of P. cinnamomi zoospores to infect unwounded suberized woody tissue of E. marginata , has important implications for mine site rehabilitation in P. cinnamomi infested areas. This is the first study to demonstrate clearly that zoospores of P. cinnamomi can infect and invade unwounded suberized tissue.     

A comparison of the direct and residual response of dairy cows to once or twice-daily milking, in late lactation

Two experiments were undertaken to examine the direct and residual responses of late lactation (mean of 232 days calved) autumn calving dairy cows (Experiment 1), and late lactation (mean of 240 days calved) spring calving dairy cows (Experiment 2), to once-daily milking. Experiments 1 and 2 involved 50 and 44 Holstein–Friesian dairy cows respectively. In each of the two experiments, cows were milked either once daily (ODM) or twice daily (TDM), during the late lactation period (mean of 79 and 66 days in Experiments 1 and 2 respectively). Cows in Experiment 1 were managed within a grazing system, and were offered 3.0 kg of concentrate/day, while cows in Experiment 2 were housed, and offered grass silage supplemented with 6.0 kg concentrate/day. Forty-one cows from Experiment 1, and 32 cows from Experiment 2, completed the first eight weeks of the subsequent lactation on a twice-daily milking regime. Food intakes were not measured in Experiment 1, while treatment had no significant effect on dry matter intake in Experiment 2 (P > 0.05). In each of Experiments 1 and 2, total milk output was increased with twice-daily milking (P ≤ 0.05), while milk fat (P ≤ 0.01) and protein (P < 0.001) concentrations increased with once-daily milking. Somatic cell counts were higher with animals milked once daily in Experiment 1 (P < 0.001), while not being significantly affected by milking frequency in Experiment 2 (P > 0.05). Milking frequency had no significant effect on cow live weight or on cow condition score at the point of drying off in either Experiment (P > 0.05). Milking time per cow during morning milking was unaffected by treatment in either experiment, while total daily milking time per cow (morning and evening combined) was significantly longer with the TDM treatment (P < 0.001). In Experiment 1, milk flow rates during the morning milking were higher with animals on the ODM treatment, compared to those on TDM treatment (P < 0.001), while being unaffected by treatment in Experiment 2 (P > 0.05). Neither daily milk yield, milk fat content, milk protein content, or somatic cell count during the subsequent lactation, were affected by previous lactation milking frequency in either of Experiments 1 or 2 (P > 0.05).     

Preliminary trials of the BioBaler working in Brazilian eucalypt plantations

The increasing demand for renewable energy feedstock has raised interest in growing eucalypts for fuel wood production, which is achieved by establishing very dense plantations cut every 18–24 months. The high moisture content of fresh Eucalyptus may handicap cut-and-chip operations, and offers a unique opportunity for supply chains based on baling. Therefore, the Canadian-made BioBaler was tested in Brazil on a eucalypt energy plantation, as well as on the resprouts generated by a conventional pulpwood plantation after severe frost damage. The BioBaler coped well with both crops, achieving high productivity levels: 7.1 and 3.3 t h^?1 in the energy plantation and the failed crop treatments, respectively. Harvesting cost was estimated at €13 t^?1 and €26 t^?1 for the energy plantation and the failed crop, respectively. Productivity and harvesting cost were comparable with those reported in previous studies conducted in other countries on similar crops. Productivity was directly proportional to field stocking. Future studies should test the machine on a wider range of work conditions and include bale extraction, storage, processing and transportation, in order to estimate an overall supply chain cost and allow direct comparison with alternative options.