Notes: Isoflurane 0.75% was compared with halothane 0.5% as the volatile supplement in a normocapnic technique for intra-ocular surgery. Both agents gave satisfactory conditions for operation with a comparable reduction in intra-ocular pressure during the procedure. Systolic arterial pressure, however, was significantly lower in the isoflurane group at the end of surgery and after tracheal extubation than in the halothane group. Isoflurane provides a useful alternative to halothane in anaesthesia for intraocular surgery.

Notes: The number of perch caught weekly in traps set in Slapton Ley, Devon has been considered. Five traps were laid in each of six regions during 1970 and 1971. The numbers caught in each region were averaged for eight lifts during 8 weeks and the logarithms of these numbers calculated. The figures obtained showed marked seasonal trends in the catch of the traps and these trends were consistent when both years were compared. If single traps were considered there was marked variability at one time which was attributed to differences in habitat. However, the combined data from each region did give a good comparison of the density of perch between regions.

Notes: SUMMARY. Perch were sampled for their stomach contents at regular intervals throughout 24 h from June until October in 1973 and from February 1975 until January 1976. They were found to feed on benthic organisms from November until April, on benthos and plankton during May and June and on perch fry and zooplankton from July until October. Perch over a wide size range feed on similar prey. Fish showed great variability in the weight of their stomach contents. A method based on a points system was developed to estimate the weight of food in the stomach for a given weight of fish at a known time. A diel feeding pattern which varied with the season was apparent from these data. Rates of gastric evacuation were assumed to be exponential and were calculated from the drop in night-time stomach content weights when food intake was assumed to be zero. The rates ranged from 0.18 mg h−1 at a mean water temperature of 11°C in May to 0.35 mg h−1 at a mean water temperature of 17°C in July. Assuming that food consumption followed a linear rate of intake, the standard Bajkov method was considered an adequate model to calculate daily food consumption. Daily food consumption (mg dry weight) was calculated for 150 g perch for all months of the year (November to April and September and October being combined). A second series of values was calculated making corrections for the time spent in the fishing gears when food intake was zero but gastric evacuation continued. Daily food consumption figures for 150g male perch based on Winberg's hypotheses (1956) and growth data showed no significant differences from this second series of values, when both were expressed in energy terms. When certain assumptions have been tested, growth data and Winberg's equations together may be a suitable method for calculating an energy budget for the Windermere perch population.

Notes: SUMMARY. Four methods were used to determine the energy content of somatic tissues of Perca fluviatilis. Two forms of direct calorimetry (both adiabatic and non-adiabatic) and wet (dichromate) oxidation gave similar results. When energy contents were calculated from proximate analysis using accepted conversion factors (9.45 cal mg−1 for lipid, 5.65 cal mg−1 for protein) results were higher than those from the other methods. The discrepancy was eliminated when a lower, directly determined energy content for the extracted lipid fraction was used.Some historic and technical aspects of the comparison are discussed.

Notes: The potential for increasing the utilization of lower quality grades and cuts of beef was dependent on controlling the level of objectionable components, such as connective tissue and developing an economical means of creating starting material for further processing. Colorimetric methods were used to distinguish connective tissue and all other objectionable components in beef chuck slices. Using the tristimuius color values (L, aL, and bL) and the color difference indices for total color difference (E), chromaticity (ΔC) and the yellowness index (YI), each component was optically differentiated. These discriminations, coupled with decision models directing disposition of the various components, can be used to control an excision system for providing suitable starting material for further processing chucks into products such as restructured beef.

Notes: The principal cause of off-flavor in explosion-puffed, air-packed potato dice at 23°C is autoxidation. A butylated hydroxyanisole/butylated hydroxytoluene system applied to the dice retarded autoxidation and samples were stored successfully for 12 months. The standard (nitrogen-pack, 23°C) was not significantly different from samples stored at -18°C. A trained taste panel found significant deterioration in air-packed samples, without antioxidant, after 3 months. Gas-liquid chromatographic analysis of the headspace in all samples allowed the monitoring of n-hexanal. Relative concentrations of this compound correlated highly with flavor degradation. Explosion-puffed potato dice showed similar storage stability when packaged in oxygen scavenger pouches or in nitrogen. Pouches, however, showed susceptibility to pinhole leaks.

Notes: Results are presented from a survey of walleye and northern pike in Ethel, Marie and Wolf Lakes, Alberta conducted May-September, 1983. Three types of experimental gill net were fished, mainly inshore. Northern pike were abundant in all three lakes but white sucker and yellow perch also were common. Walleye were caught in largest numbers in Wolf Lake. Age and growth of both walleye and northern pike were determined from examination of the opercular bones. The walleye in the three lakes were represented by a few strong year classes but there was no synchronism between the lakes. The strong 1975 year class in Ethel and Wolf Lakes may have been correlated with high spring precipitation and heavy run-off. Although there were dominant year classes in the northern pike populations (especially the 1979 year class) the variability was not so marked as in the walleye. There were no significant differences between length-at-age for year classes of walleye in Ethel and Marie or northern pike in all three lakes. In Wolf Lake the 1978 and 1979 year classes grew faster than in previous years. Walleye and northern pike growth was well described by the von Bertalanffy growth model. Females of both species grew to a greater ultimate length and had a longer lifespan than the males. Fecundity data are presented for walleye from Wolf Lake (log10 absolute fecundity = 0.856 + 2.441 log10 length) and northern pike from Marie Lake (log10 absolute fecundity =−2.671+4.052 log10 length). The stomach contents of both species were examined during May and June. The majority of walleye had empty stomachs. Walleye and northern pike in Ethel and Wolf Lakes fed on a variety of fish and invertebrate species but both fed mainly on fish (in particular whitefish) in Marie Lake. The similarity of diet suggests competition for prey species. A walleye yield to commercial fishermen of c. 0.69 kg ha−1 year−1 in Wolf Lake has made up 8% of the total catch. Since 1970/71 when mesh size of nets was increased, the yield has been reduced to c. 0.30 kg ha−1 year−1. Anglers remove an additional c. 0.48 kg ha−1 year−1 walleye from Wolf Lake. Northern pike yields to commercial fishermen have been c. 2.00 kg ha−1 year−1 in Wolf Lake. Ethel and Marie Lakes have yielded only poor catches of walleye and northern pike. A yield model was used to illustrate that faster-growing northern pike have higher potential yields than walleye. Walleye produce higher yields in Wolf Lake than in Marie Lake, the reverse being true for northern pike. It is suggested that northern pike could be cropped at a higher rate in Marie and Wolf Lakes with a possible improvement in walleye stocks.

Notes: Three types of multi-mesh gillnet were fished in three lakes in Alberta during spring and summer of 1983. Eight species offish were caught in a total of 89 lifts. The variability of the catches was analysed after a transformation into y= log (x+1). For the major species (apart from yellow perch) there were remarkable similarities between species for error variances associated with catches from nets and from meshes. The total error variance associated with a catch from any net was 0-0575 (C.V. = 59-7%). Total error variance associated with a catch from a single mesh was 0-0852 (C.V. = 75-6%). These values are compared to those from other studies and an error variance estimate of 0-0868 (C.V. = 76-5%) was considered to be an appropriate value for gillnet catches in fresh waters. In sampling programmes more than six nets would need to be used for confidence limits to be below half or more than twice the geometric mean.

Notes: Abstract. The geographical distribution of an epizootic of perch Perca fluviatilis L., characterized by severe epidermal lesions and marked fish kills, is described. A wide variety of fungal and bacterial infections were found in diseased fish but the evidence suggests that they were not the primary cause of this condition. The primary pathogenic agent (assuming that it exists) or predisposing environmental factor has yet to be discovered. The severity of this disease is illustrated by monitoring the course of the epizootic in the perch population in Windermere. All age groups of fish were affected during the course of one year although the fish at spawning time appeared to be particularly vulnerable. There was a dramatic increase in the perch mortality in Windermere in 1976 and it is estimated that over 98% of the adult population (over 1 million fish) died in that year.

Notes: Scientists at Eastern Regional Research Center have successfully continuously explosion-puffed potatoes for dehydration. By using a newly designed and fabricated puffing unit, they demonstrated that this equipment can be used in a continuous explosion puffing system (CEPS). Equipment development was carried out to effect commercial reliability, acceptable products and a high output rate. Potato dice, 1.0 cm (3/8 in.), at 27% moisture were processed in CEPS at a maximum rate of 454 kg/hr (1000 1b/hr). With mechanical refinements largely complete, an optimization study was made. Using product rehydration and flavor as criteria, a puffing pressure of 345 kilo pascals (50 psig) at a moisture content of about 26% was optimal for the 1.0 cm dice.