Habitat characteristics affecting occurrence of a fluvial species in a watershed altered by a large reservoir

Flooding river valleys following construction of dams restrict fluvial environments to reaches that were formerly headwaters. Whether remaining habitat is suitable for all life stages of fluvial species is poorly understood. A fluvial species, Arctic grayling Thymallus arcticus, showed a dramatic decline following flooding of the Upper Peace River and the formation of the Williston Reservoir. We related landscape and field site‐specific features with occurrence of juvenile Arctic grayling using an information theoretic approach. For the landscape model, an association was identified between stream order and Arctic grayling occurrence although stream order alone was a poor predictor. A positive association between juvenile Arctic grayling occurrence and distance from the Williston reservoir and stream order, as well as a negative association with water temperature and temperature variance, was deemed important for the field site model. Both modelling approaches indicated size of stream system to be an important influence on occurrence of juvenile grayling in the Williston watershed. River length required for suitable river habitat for salmonids has not previously been identified, but should be factored into future management plans when evaluating the impact of proposed hydroelectric dams and subsequent flooding of river systems.     

Comparative persistence of pesticides on selected cultivars of specialty vegetables

The behavior and dissipation of several pesticides on selected cultivars of specialty vegetable crops were compared to determine appropriate preharvest intervals for compliance with maximum residue limits. To reduce application variability, a tank mix of pesticides was applied for each trial. Residues of eight pesticides applied to bok choi, Chinese broccoli, and fuzzy squash were similar for the two leafy vegetables; residues were higher than on squash because of the latter's larger mass-to-surface area ratio. Whereas residues of five of the nine pesticides applied to cabbage, Chinese cabbage, and bok choi did not differ significantly from 3 to 14 days after application, residues of cypermethrin and three fungicides were significantly higher on Chinese cabbage and bok choi. The residue deposits of the pesticides were about 50% lower on Chinese cabbage and 90% lower on cabbage than on bok choi. Dissipation of residues on different cultivars of lettuce and cabbage were compared after application of nine pesticides. With the exception of captan, residues on head lettuce were lower than on the other lettuces on day 1; cultivar differences were not significant for most of the nine applied pesticides on days 3 and 8. Generally, residues of the nine individual pesticides on storage cabbage, savoy cabbage, Chinese cabbage, and tah tsai did not differ significantly from day 1 to day 7 after application. Residue concentrations were generally significantly higher on bok choi than on the other cultivars. Residue deposits generally correlated with the rate of application; residues of captan, however, were about 50% of the predicted value. Significant differences in deposit and dissipation were observed among cultivars and pesticides, with dramatic initial decreases for diazinon and parathion. Because of their higher exposed surface area-to-mass ratios, leafier crops had higher residue concentrations than head varieties. Residues on lettuce cultivars were higher than on the cabbages. The results clearly indicate that structure significantly affects residue deposit and dissipation, and pesticide recommendations cannot always be extended to specialty crops without an investigation of the changes in preharvest intervals to prevent violations of the maximum residue limits.     

Initial pesticide residues in relation to vapour pressure

Field tests, in which several insecticides were applied at equal rates by ground sprayer to oats, rye and alfalfa, showed that residues 1 h after application were much lower for highly volatile compounds than for those of lower volatility. Varying the distance from spray release to target canopy from 10 to 40 cm did not significantly affect the deposits. Results indicate that applying insecticides with a vapour pressure greater than about 10^?4 mmHg (20°C) in aqueous media is very inefficient.     

Fatal ancylostomiasis in a dog

Abstract

Extract

Canine hookworm disease is a general term used to describe morbidity associated with infection by certain small-intestinal nematode parasites of dogs. It is now known, however, that there are at leastthree and possibly four species of canine hookworms and that these vary considerably in their pathogenicity (Miller, 1971 Miller, T. A. 1971. “Vaccination against the canine hookworm diseases”. In Advances in Parasitology, Edited by: Dawes, B. Vol. 9, 153–183. London: Academic Press.  [Google Scholar]). In New Zealand, the occurrence of only one of these species, Unoinaria stenocephalia, appears to be recorded in the literature although verbal reports of the existence of a second, Ancylostoma caninum, have been received occasionally. This report describes the occurrence of an A. caninum infection in a dog which resulted in what is believed to be the first recorded case of fatal ancylostomiasis in New Zealand.     

Chlorination in poultry processing

The effect of relatively high concentrations of available chlorine in the tanks used for chilling freshly eviscerated chickens on their shelf‐life at 1° C. and on their appearance, taste and odour has been studied.

The nominal initial concentrations of available chlorine that were used were (in p.p.m.): 50, 100, 200, 400, 1000, 2000, 4000 and 8000. The carcasses were immersed in the slush ice for 4 hr. and after this time 20–30 per cent of the initial level, up to 200 p.p.m., was detected as combined chlorine when the contents of the tanks had been stirred between the 2nd and 3rd hr.

Under these conditions and with an initial nominal concentration of available chlorine of 200 p.p.m. shelf‐life at 1° C. was extended by about 20 per cent. Panels of observers detected no significant effect on appearance, taste or odour and the results of a small‐scale consumer trial supported these findings. Initial concentrations of available chlorine of 500 p.p.m. and more resulted in tainted carcasses.